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This is to be consistent with StringSet and ultimately with the standard library's associative container insert function. This lead to updating SmallSet::insert to return pair<iterator, bool>, and then to update SmallPtrSet::insert to return pair<iterator, bool>, and then to update all the existing users of those functions... git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222334 91177308-0d34-0410-b5e6-96231b3b80d8
1495 lines
53 KiB
C++
1495 lines
53 KiB
C++
//===- MergeFunctions.cpp - Merge identical functions ---------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass looks for equivalent functions that are mergable and folds them.
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//
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// Order relation is defined on set of functions. It was made through
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// special function comparison procedure that returns
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// 0 when functions are equal,
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// -1 when Left function is less than right function, and
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// 1 for opposite case. We need total-ordering, so we need to maintain
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// four properties on the functions set:
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// a <= a (reflexivity)
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// if a <= b and b <= a then a = b (antisymmetry)
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// if a <= b and b <= c then a <= c (transitivity).
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// for all a and b: a <= b or b <= a (totality).
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//
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// Comparison iterates through each instruction in each basic block.
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// Functions are kept on binary tree. For each new function F we perform
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// lookup in binary tree.
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// In practice it works the following way:
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// -- We define Function* container class with custom "operator<" (FunctionPtr).
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// -- "FunctionPtr" instances are stored in std::set collection, so every
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// std::set::insert operation will give you result in log(N) time.
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//
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// When a match is found the functions are folded. If both functions are
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// overridable, we move the functionality into a new internal function and
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// leave two overridable thunks to it.
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//
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//===----------------------------------------------------------------------===//
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//
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// Future work:
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//
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// * virtual functions.
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//
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// Many functions have their address taken by the virtual function table for
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// the object they belong to. However, as long as it's only used for a lookup
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// and call, this is irrelevant, and we'd like to fold such functions.
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//
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// * be smarter about bitcasts.
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//
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// In order to fold functions, we will sometimes add either bitcast instructions
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// or bitcast constant expressions. Unfortunately, this can confound further
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// analysis since the two functions differ where one has a bitcast and the
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// other doesn't. We should learn to look through bitcasts.
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//
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// * Compare complex types with pointer types inside.
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// * Compare cross-reference cases.
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// * Compare complex expressions.
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//
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// All the three issues above could be described as ability to prove that
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// fA == fB == fC == fE == fF == fG in example below:
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//
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// void fA() {
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// fB();
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// }
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// void fB() {
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// fA();
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// }
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//
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// void fE() {
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// fF();
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// }
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// void fF() {
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// fG();
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// }
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// void fG() {
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// fE();
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// }
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//
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// Simplest cross-reference case (fA <--> fB) was implemented in previous
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// versions of MergeFunctions, though it presented only in two function pairs
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// in test-suite (that counts >50k functions)
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// Though possibility to detect complex cross-referencing (e.g.: A->B->C->D->A)
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// could cover much more cases.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/IPO.h"
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#include "llvm/ADT/DenseSet.h"
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#include "llvm/ADT/FoldingSet.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/IR/CallSite.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/InlineAsm.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/LLVMContext.h"
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#include "llvm/IR/Module.h"
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#include "llvm/IR/Operator.h"
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#include "llvm/IR/ValueHandle.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include <vector>
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using namespace llvm;
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#define DEBUG_TYPE "mergefunc"
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STATISTIC(NumFunctionsMerged, "Number of functions merged");
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STATISTIC(NumThunksWritten, "Number of thunks generated");
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STATISTIC(NumAliasesWritten, "Number of aliases generated");
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STATISTIC(NumDoubleWeak, "Number of new functions created");
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static cl::opt<unsigned> NumFunctionsForSanityCheck(
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"mergefunc-sanity",
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cl::desc("How many functions in module could be used for "
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"MergeFunctions pass sanity check. "
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"'0' disables this check. Works only with '-debug' key."),
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cl::init(0), cl::Hidden);
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namespace {
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/// FunctionComparator - Compares two functions to determine whether or not
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/// they will generate machine code with the same behaviour. DataLayout is
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/// used if available. The comparator always fails conservatively (erring on the
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/// side of claiming that two functions are different).
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class FunctionComparator {
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public:
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FunctionComparator(const DataLayout *DL, const Function *F1,
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const Function *F2)
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: FnL(F1), FnR(F2), DL(DL) {}
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/// Test whether the two functions have equivalent behaviour.
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int compare();
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private:
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/// Test whether two basic blocks have equivalent behaviour.
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int compare(const BasicBlock *BBL, const BasicBlock *BBR);
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/// Constants comparison.
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/// Its analog to lexicographical comparison between hypothetical numbers
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/// of next format:
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/// <bitcastability-trait><raw-bit-contents>
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///
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/// 1. Bitcastability.
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/// Check whether L's type could be losslessly bitcasted to R's type.
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/// On this stage method, in case when lossless bitcast is not possible
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/// method returns -1 or 1, thus also defining which type is greater in
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/// context of bitcastability.
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/// Stage 0: If types are equal in terms of cmpTypes, then we can go straight
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/// to the contents comparison.
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/// If types differ, remember types comparison result and check
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/// whether we still can bitcast types.
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/// Stage 1: Types that satisfies isFirstClassType conditions are always
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/// greater then others.
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/// Stage 2: Vector is greater then non-vector.
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/// If both types are vectors, then vector with greater bitwidth is
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/// greater.
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/// If both types are vectors with the same bitwidth, then types
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/// are bitcastable, and we can skip other stages, and go to contents
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/// comparison.
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/// Stage 3: Pointer types are greater than non-pointers. If both types are
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/// pointers of the same address space - go to contents comparison.
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/// Different address spaces: pointer with greater address space is
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/// greater.
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/// Stage 4: Types are neither vectors, nor pointers. And they differ.
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/// We don't know how to bitcast them. So, we better don't do it,
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/// and return types comparison result (so it determines the
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/// relationship among constants we don't know how to bitcast).
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///
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/// Just for clearance, let's see how the set of constants could look
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/// on single dimension axis:
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///
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/// [NFCT], [FCT, "others"], [FCT, pointers], [FCT, vectors]
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/// Where: NFCT - Not a FirstClassType
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/// FCT - FirstClassTyp:
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///
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/// 2. Compare raw contents.
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/// It ignores types on this stage and only compares bits from L and R.
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/// Returns 0, if L and R has equivalent contents.
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/// -1 or 1 if values are different.
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/// Pretty trivial:
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/// 2.1. If contents are numbers, compare numbers.
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/// Ints with greater bitwidth are greater. Ints with same bitwidths
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/// compared by their contents.
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/// 2.2. "And so on". Just to avoid discrepancies with comments
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/// perhaps it would be better to read the implementation itself.
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/// 3. And again about overall picture. Let's look back at how the ordered set
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/// of constants will look like:
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/// [NFCT], [FCT, "others"], [FCT, pointers], [FCT, vectors]
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///
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/// Now look, what could be inside [FCT, "others"], for example:
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/// [FCT, "others"] =
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/// [
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/// [double 0.1], [double 1.23],
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/// [i32 1], [i32 2],
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/// { double 1.0 }, ; StructTyID, NumElements = 1
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/// { i32 1 }, ; StructTyID, NumElements = 1
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/// { double 1, i32 1 }, ; StructTyID, NumElements = 2
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/// { i32 1, double 1 } ; StructTyID, NumElements = 2
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/// ]
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///
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/// Let's explain the order. Float numbers will be less than integers, just
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/// because of cmpType terms: FloatTyID < IntegerTyID.
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/// Floats (with same fltSemantics) are sorted according to their value.
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/// Then you can see integers, and they are, like a floats,
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/// could be easy sorted among each others.
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/// The structures. Structures are grouped at the tail, again because of their
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/// TypeID: StructTyID > IntegerTyID > FloatTyID.
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/// Structures with greater number of elements are greater. Structures with
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/// greater elements going first are greater.
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/// The same logic with vectors, arrays and other possible complex types.
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///
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/// Bitcastable constants.
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/// Let's assume, that some constant, belongs to some group of
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/// "so-called-equal" values with different types, and at the same time
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/// belongs to another group of constants with equal types
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/// and "really" equal values.
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///
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/// Now, prove that this is impossible:
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///
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/// If constant A with type TyA is bitcastable to B with type TyB, then:
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/// 1. All constants with equal types to TyA, are bitcastable to B. Since
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/// those should be vectors (if TyA is vector), pointers
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/// (if TyA is pointer), or else (if TyA equal to TyB), those types should
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/// be equal to TyB.
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/// 2. All constants with non-equal, but bitcastable types to TyA, are
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/// bitcastable to B.
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/// Once again, just because we allow it to vectors and pointers only.
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/// This statement could be expanded as below:
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/// 2.1. All vectors with equal bitwidth to vector A, has equal bitwidth to
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/// vector B, and thus bitcastable to B as well.
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/// 2.2. All pointers of the same address space, no matter what they point to,
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/// bitcastable. So if C is pointer, it could be bitcasted to A and to B.
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/// So any constant equal or bitcastable to A is equal or bitcastable to B.
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/// QED.
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///
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/// In another words, for pointers and vectors, we ignore top-level type and
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/// look at their particular properties (bit-width for vectors, and
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/// address space for pointers).
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/// If these properties are equal - compare their contents.
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int cmpConstants(const Constant *L, const Constant *R);
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/// Assign or look up previously assigned numbers for the two values, and
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/// return whether the numbers are equal. Numbers are assigned in the order
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/// visited.
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/// Comparison order:
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/// Stage 0: Value that is function itself is always greater then others.
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/// If left and right values are references to their functions, then
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/// they are equal.
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/// Stage 1: Constants are greater than non-constants.
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/// If both left and right are constants, then the result of
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/// cmpConstants is used as cmpValues result.
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/// Stage 2: InlineAsm instances are greater than others. If both left and
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/// right are InlineAsm instances, InlineAsm* pointers casted to
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/// integers and compared as numbers.
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/// Stage 3: For all other cases we compare order we meet these values in
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/// their functions. If right value was met first during scanning,
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/// then left value is greater.
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/// In another words, we compare serial numbers, for more details
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/// see comments for sn_mapL and sn_mapR.
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int cmpValues(const Value *L, const Value *R);
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/// Compare two Instructions for equivalence, similar to
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/// Instruction::isSameOperationAs but with modifications to the type
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/// comparison.
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/// Stages are listed in "most significant stage first" order:
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/// On each stage below, we do comparison between some left and right
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/// operation parts. If parts are non-equal, we assign parts comparison
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/// result to the operation comparison result and exit from method.
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/// Otherwise we proceed to the next stage.
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/// Stages:
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/// 1. Operations opcodes. Compared as numbers.
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/// 2. Number of operands.
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/// 3. Operation types. Compared with cmpType method.
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/// 4. Compare operation subclass optional data as stream of bytes:
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/// just convert it to integers and call cmpNumbers.
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/// 5. Compare in operation operand types with cmpType in
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/// most significant operand first order.
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/// 6. Last stage. Check operations for some specific attributes.
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/// For example, for Load it would be:
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/// 6.1.Load: volatile (as boolean flag)
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/// 6.2.Load: alignment (as integer numbers)
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/// 6.3.Load: synch-scope (as integer numbers)
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/// 6.4.Load: range metadata (as integer numbers)
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/// On this stage its better to see the code, since its not more than 10-15
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/// strings for particular instruction, and could change sometimes.
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int cmpOperations(const Instruction *L, const Instruction *R) const;
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/// Compare two GEPs for equivalent pointer arithmetic.
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/// Parts to be compared for each comparison stage,
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/// most significant stage first:
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/// 1. Address space. As numbers.
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/// 2. Constant offset, (if "DataLayout *DL" field is not NULL,
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/// using GEPOperator::accumulateConstantOffset method).
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/// 3. Pointer operand type (using cmpType method).
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/// 4. Number of operands.
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/// 5. Compare operands, using cmpValues method.
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int cmpGEPs(const GEPOperator *GEPL, const GEPOperator *GEPR);
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int cmpGEPs(const GetElementPtrInst *GEPL, const GetElementPtrInst *GEPR) {
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return cmpGEPs(cast<GEPOperator>(GEPL), cast<GEPOperator>(GEPR));
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}
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/// cmpType - compares two types,
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/// defines total ordering among the types set.
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///
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/// Return values:
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/// 0 if types are equal,
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/// -1 if Left is less than Right,
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/// +1 if Left is greater than Right.
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///
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/// Description:
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/// Comparison is broken onto stages. Like in lexicographical comparison
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/// stage coming first has higher priority.
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/// On each explanation stage keep in mind total ordering properties.
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///
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/// 0. Before comparison we coerce pointer types of 0 address space to
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/// integer.
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/// We also don't bother with same type at left and right, so
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/// just return 0 in this case.
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///
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/// 1. If types are of different kind (different type IDs).
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/// Return result of type IDs comparison, treating them as numbers.
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/// 2. If types are vectors or integers, compare Type* values as numbers.
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/// 3. Types has same ID, so check whether they belongs to the next group:
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/// * Void
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/// * Float
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/// * Double
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/// * X86_FP80
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/// * FP128
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/// * PPC_FP128
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/// * Label
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/// * Metadata
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/// If so - return 0, yes - we can treat these types as equal only because
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/// their IDs are same.
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/// 4. If Left and Right are pointers, return result of address space
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/// comparison (numbers comparison). We can treat pointer types of same
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/// address space as equal.
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/// 5. If types are complex.
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/// Then both Left and Right are to be expanded and their element types will
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/// be checked with the same way. If we get Res != 0 on some stage, return it.
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/// Otherwise return 0.
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/// 6. For all other cases put llvm_unreachable.
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int cmpTypes(Type *TyL, Type *TyR) const;
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int cmpNumbers(uint64_t L, uint64_t R) const;
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int cmpAPInts(const APInt &L, const APInt &R) const;
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int cmpAPFloats(const APFloat &L, const APFloat &R) const;
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int cmpStrings(StringRef L, StringRef R) const;
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int cmpAttrs(const AttributeSet L, const AttributeSet R) const;
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// The two functions undergoing comparison.
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const Function *FnL, *FnR;
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const DataLayout *DL;
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/// Assign serial numbers to values from left function, and values from
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/// right function.
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/// Explanation:
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/// Being comparing functions we need to compare values we meet at left and
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/// right sides.
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/// Its easy to sort things out for external values. It just should be
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/// the same value at left and right.
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/// But for local values (those were introduced inside function body)
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/// we have to ensure they were introduced at exactly the same place,
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/// and plays the same role.
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/// Let's assign serial number to each value when we meet it first time.
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/// Values that were met at same place will be with same serial numbers.
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/// In this case it would be good to explain few points about values assigned
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/// to BBs and other ways of implementation (see below).
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///
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/// 1. Safety of BB reordering.
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/// It's safe to change the order of BasicBlocks in function.
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/// Relationship with other functions and serial numbering will not be
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/// changed in this case.
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/// As follows from FunctionComparator::compare(), we do CFG walk: we start
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/// from the entry, and then take each terminator. So it doesn't matter how in
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/// fact BBs are ordered in function. And since cmpValues are called during
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/// this walk, the numbering depends only on how BBs located inside the CFG.
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/// So the answer is - yes. We will get the same numbering.
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///
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/// 2. Impossibility to use dominance properties of values.
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/// If we compare two instruction operands: first is usage of local
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/// variable AL from function FL, and second is usage of local variable AR
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/// from FR, we could compare their origins and check whether they are
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/// defined at the same place.
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/// But, we are still not able to compare operands of PHI nodes, since those
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/// could be operands from further BBs we didn't scan yet.
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/// So it's impossible to use dominance properties in general.
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DenseMap<const Value*, int> sn_mapL, sn_mapR;
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};
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class FunctionNode {
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AssertingVH<Function> F;
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const DataLayout *DL;
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public:
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FunctionNode(Function *F, const DataLayout *DL) : F(F), DL(DL) {}
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Function *getFunc() const { return F; }
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void release() { F = 0; }
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bool operator<(const FunctionNode &RHS) const {
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return (FunctionComparator(DL, F, RHS.getFunc()).compare()) == -1;
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}
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};
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}
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int FunctionComparator::cmpNumbers(uint64_t L, uint64_t R) const {
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if (L < R) return -1;
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if (L > R) return 1;
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return 0;
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}
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int FunctionComparator::cmpAPInts(const APInt &L, const APInt &R) const {
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if (int Res = cmpNumbers(L.getBitWidth(), R.getBitWidth()))
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return Res;
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if (L.ugt(R)) return 1;
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if (R.ugt(L)) return -1;
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return 0;
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}
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int FunctionComparator::cmpAPFloats(const APFloat &L, const APFloat &R) const {
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if (int Res = cmpNumbers((uint64_t)&L.getSemantics(),
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(uint64_t)&R.getSemantics()))
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return Res;
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return cmpAPInts(L.bitcastToAPInt(), R.bitcastToAPInt());
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}
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int FunctionComparator::cmpStrings(StringRef L, StringRef R) const {
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// Prevent heavy comparison, compare sizes first.
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if (int Res = cmpNumbers(L.size(), R.size()))
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return Res;
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// Compare strings lexicographically only when it is necessary: only when
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// strings are equal in size.
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return L.compare(R);
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}
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int FunctionComparator::cmpAttrs(const AttributeSet L,
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const AttributeSet R) const {
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if (int Res = cmpNumbers(L.getNumSlots(), R.getNumSlots()))
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return Res;
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|
for (unsigned i = 0, e = L.getNumSlots(); i != e; ++i) {
|
|
AttributeSet::iterator LI = L.begin(i), LE = L.end(i), RI = R.begin(i),
|
|
RE = R.end(i);
|
|
for (; LI != LE && RI != RE; ++LI, ++RI) {
|
|
Attribute LA = *LI;
|
|
Attribute RA = *RI;
|
|
if (LA < RA)
|
|
return -1;
|
|
if (RA < LA)
|
|
return 1;
|
|
}
|
|
if (LI != LE)
|
|
return 1;
|
|
if (RI != RE)
|
|
return -1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/// Constants comparison:
|
|
/// 1. Check whether type of L constant could be losslessly bitcasted to R
|
|
/// type.
|
|
/// 2. Compare constant contents.
|
|
/// For more details see declaration comments.
|
|
int FunctionComparator::cmpConstants(const Constant *L, const Constant *R) {
|
|
|
|
Type *TyL = L->getType();
|
|
Type *TyR = R->getType();
|
|
|
|
// Check whether types are bitcastable. This part is just re-factored
|
|
// Type::canLosslesslyBitCastTo method, but instead of returning true/false,
|
|
// we also pack into result which type is "less" for us.
|
|
int TypesRes = cmpTypes(TyL, TyR);
|
|
if (TypesRes != 0) {
|
|
// Types are different, but check whether we can bitcast them.
|
|
if (!TyL->isFirstClassType()) {
|
|
if (TyR->isFirstClassType())
|
|
return -1;
|
|
// Neither TyL nor TyR are values of first class type. Return the result
|
|
// of comparing the types
|
|
return TypesRes;
|
|
}
|
|
if (!TyR->isFirstClassType()) {
|
|
if (TyL->isFirstClassType())
|
|
return 1;
|
|
return TypesRes;
|
|
}
|
|
|
|
// Vector -> Vector conversions are always lossless if the two vector types
|
|
// have the same size, otherwise not.
|
|
unsigned TyLWidth = 0;
|
|
unsigned TyRWidth = 0;
|
|
|
|
if (const VectorType *VecTyL = dyn_cast<VectorType>(TyL))
|
|
TyLWidth = VecTyL->getBitWidth();
|
|
if (const VectorType *VecTyR = dyn_cast<VectorType>(TyR))
|
|
TyRWidth = VecTyR->getBitWidth();
|
|
|
|
if (TyLWidth != TyRWidth)
|
|
return cmpNumbers(TyLWidth, TyRWidth);
|
|
|
|
// Zero bit-width means neither TyL nor TyR are vectors.
|
|
if (!TyLWidth) {
|
|
PointerType *PTyL = dyn_cast<PointerType>(TyL);
|
|
PointerType *PTyR = dyn_cast<PointerType>(TyR);
|
|
if (PTyL && PTyR) {
|
|
unsigned AddrSpaceL = PTyL->getAddressSpace();
|
|
unsigned AddrSpaceR = PTyR->getAddressSpace();
|
|
if (int Res = cmpNumbers(AddrSpaceL, AddrSpaceR))
|
|
return Res;
|
|
}
|
|
if (PTyL)
|
|
return 1;
|
|
if (PTyR)
|
|
return -1;
|
|
|
|
// TyL and TyR aren't vectors, nor pointers. We don't know how to
|
|
// bitcast them.
|
|
return TypesRes;
|
|
}
|
|
}
|
|
|
|
// OK, types are bitcastable, now check constant contents.
|
|
|
|
if (L->isNullValue() && R->isNullValue())
|
|
return TypesRes;
|
|
if (L->isNullValue() && !R->isNullValue())
|
|
return 1;
|
|
if (!L->isNullValue() && R->isNullValue())
|
|
return -1;
|
|
|
|
if (int Res = cmpNumbers(L->getValueID(), R->getValueID()))
|
|
return Res;
|
|
|
|
switch (L->getValueID()) {
|
|
case Value::UndefValueVal: return TypesRes;
|
|
case Value::ConstantIntVal: {
|
|
const APInt &LInt = cast<ConstantInt>(L)->getValue();
|
|
const APInt &RInt = cast<ConstantInt>(R)->getValue();
|
|
return cmpAPInts(LInt, RInt);
|
|
}
|
|
case Value::ConstantFPVal: {
|
|
const APFloat &LAPF = cast<ConstantFP>(L)->getValueAPF();
|
|
const APFloat &RAPF = cast<ConstantFP>(R)->getValueAPF();
|
|
return cmpAPFloats(LAPF, RAPF);
|
|
}
|
|
case Value::ConstantArrayVal: {
|
|
const ConstantArray *LA = cast<ConstantArray>(L);
|
|
const ConstantArray *RA = cast<ConstantArray>(R);
|
|
uint64_t NumElementsL = cast<ArrayType>(TyL)->getNumElements();
|
|
uint64_t NumElementsR = cast<ArrayType>(TyR)->getNumElements();
|
|
if (int Res = cmpNumbers(NumElementsL, NumElementsR))
|
|
return Res;
|
|
for (uint64_t i = 0; i < NumElementsL; ++i) {
|
|
if (int Res = cmpConstants(cast<Constant>(LA->getOperand(i)),
|
|
cast<Constant>(RA->getOperand(i))))
|
|
return Res;
|
|
}
|
|
return 0;
|
|
}
|
|
case Value::ConstantStructVal: {
|
|
const ConstantStruct *LS = cast<ConstantStruct>(L);
|
|
const ConstantStruct *RS = cast<ConstantStruct>(R);
|
|
unsigned NumElementsL = cast<StructType>(TyL)->getNumElements();
|
|
unsigned NumElementsR = cast<StructType>(TyR)->getNumElements();
|
|
if (int Res = cmpNumbers(NumElementsL, NumElementsR))
|
|
return Res;
|
|
for (unsigned i = 0; i != NumElementsL; ++i) {
|
|
if (int Res = cmpConstants(cast<Constant>(LS->getOperand(i)),
|
|
cast<Constant>(RS->getOperand(i))))
|
|
return Res;
|
|
}
|
|
return 0;
|
|
}
|
|
case Value::ConstantVectorVal: {
|
|
const ConstantVector *LV = cast<ConstantVector>(L);
|
|
const ConstantVector *RV = cast<ConstantVector>(R);
|
|
unsigned NumElementsL = cast<VectorType>(TyL)->getNumElements();
|
|
unsigned NumElementsR = cast<VectorType>(TyR)->getNumElements();
|
|
if (int Res = cmpNumbers(NumElementsL, NumElementsR))
|
|
return Res;
|
|
for (uint64_t i = 0; i < NumElementsL; ++i) {
|
|
if (int Res = cmpConstants(cast<Constant>(LV->getOperand(i)),
|
|
cast<Constant>(RV->getOperand(i))))
|
|
return Res;
|
|
}
|
|
return 0;
|
|
}
|
|
case Value::ConstantExprVal: {
|
|
const ConstantExpr *LE = cast<ConstantExpr>(L);
|
|
const ConstantExpr *RE = cast<ConstantExpr>(R);
|
|
unsigned NumOperandsL = LE->getNumOperands();
|
|
unsigned NumOperandsR = RE->getNumOperands();
|
|
if (int Res = cmpNumbers(NumOperandsL, NumOperandsR))
|
|
return Res;
|
|
for (unsigned i = 0; i < NumOperandsL; ++i) {
|
|
if (int Res = cmpConstants(cast<Constant>(LE->getOperand(i)),
|
|
cast<Constant>(RE->getOperand(i))))
|
|
return Res;
|
|
}
|
|
return 0;
|
|
}
|
|
case Value::FunctionVal:
|
|
case Value::GlobalVariableVal:
|
|
case Value::GlobalAliasVal:
|
|
default: // Unknown constant, cast L and R pointers to numbers and compare.
|
|
return cmpNumbers((uint64_t)L, (uint64_t)R);
|
|
}
|
|
}
|
|
|
|
/// cmpType - compares two types,
|
|
/// defines total ordering among the types set.
|
|
/// See method declaration comments for more details.
|
|
int FunctionComparator::cmpTypes(Type *TyL, Type *TyR) const {
|
|
|
|
PointerType *PTyL = dyn_cast<PointerType>(TyL);
|
|
PointerType *PTyR = dyn_cast<PointerType>(TyR);
|
|
|
|
if (DL) {
|
|
if (PTyL && PTyL->getAddressSpace() == 0) TyL = DL->getIntPtrType(TyL);
|
|
if (PTyR && PTyR->getAddressSpace() == 0) TyR = DL->getIntPtrType(TyR);
|
|
}
|
|
|
|
if (TyL == TyR)
|
|
return 0;
|
|
|
|
if (int Res = cmpNumbers(TyL->getTypeID(), TyR->getTypeID()))
|
|
return Res;
|
|
|
|
switch (TyL->getTypeID()) {
|
|
default:
|
|
llvm_unreachable("Unknown type!");
|
|
// Fall through in Release mode.
|
|
case Type::IntegerTyID:
|
|
case Type::VectorTyID:
|
|
// TyL == TyR would have returned true earlier.
|
|
return cmpNumbers((uint64_t)TyL, (uint64_t)TyR);
|
|
|
|
case Type::VoidTyID:
|
|
case Type::FloatTyID:
|
|
case Type::DoubleTyID:
|
|
case Type::X86_FP80TyID:
|
|
case Type::FP128TyID:
|
|
case Type::PPC_FP128TyID:
|
|
case Type::LabelTyID:
|
|
case Type::MetadataTyID:
|
|
return 0;
|
|
|
|
case Type::PointerTyID: {
|
|
assert(PTyL && PTyR && "Both types must be pointers here.");
|
|
return cmpNumbers(PTyL->getAddressSpace(), PTyR->getAddressSpace());
|
|
}
|
|
|
|
case Type::StructTyID: {
|
|
StructType *STyL = cast<StructType>(TyL);
|
|
StructType *STyR = cast<StructType>(TyR);
|
|
if (STyL->getNumElements() != STyR->getNumElements())
|
|
return cmpNumbers(STyL->getNumElements(), STyR->getNumElements());
|
|
|
|
if (STyL->isPacked() != STyR->isPacked())
|
|
return cmpNumbers(STyL->isPacked(), STyR->isPacked());
|
|
|
|
for (unsigned i = 0, e = STyL->getNumElements(); i != e; ++i) {
|
|
if (int Res = cmpTypes(STyL->getElementType(i), STyR->getElementType(i)))
|
|
return Res;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
case Type::FunctionTyID: {
|
|
FunctionType *FTyL = cast<FunctionType>(TyL);
|
|
FunctionType *FTyR = cast<FunctionType>(TyR);
|
|
if (FTyL->getNumParams() != FTyR->getNumParams())
|
|
return cmpNumbers(FTyL->getNumParams(), FTyR->getNumParams());
|
|
|
|
if (FTyL->isVarArg() != FTyR->isVarArg())
|
|
return cmpNumbers(FTyL->isVarArg(), FTyR->isVarArg());
|
|
|
|
if (int Res = cmpTypes(FTyL->getReturnType(), FTyR->getReturnType()))
|
|
return Res;
|
|
|
|
for (unsigned i = 0, e = FTyL->getNumParams(); i != e; ++i) {
|
|
if (int Res = cmpTypes(FTyL->getParamType(i), FTyR->getParamType(i)))
|
|
return Res;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
case Type::ArrayTyID: {
|
|
ArrayType *ATyL = cast<ArrayType>(TyL);
|
|
ArrayType *ATyR = cast<ArrayType>(TyR);
|
|
if (ATyL->getNumElements() != ATyR->getNumElements())
|
|
return cmpNumbers(ATyL->getNumElements(), ATyR->getNumElements());
|
|
return cmpTypes(ATyL->getElementType(), ATyR->getElementType());
|
|
}
|
|
}
|
|
}
|
|
|
|
// Determine whether the two operations are the same except that pointer-to-A
|
|
// and pointer-to-B are equivalent. This should be kept in sync with
|
|
// Instruction::isSameOperationAs.
|
|
// Read method declaration comments for more details.
|
|
int FunctionComparator::cmpOperations(const Instruction *L,
|
|
const Instruction *R) const {
|
|
// Differences from Instruction::isSameOperationAs:
|
|
// * replace type comparison with calls to isEquivalentType.
|
|
// * we test for I->hasSameSubclassOptionalData (nuw/nsw/tail) at the top
|
|
// * because of the above, we don't test for the tail bit on calls later on
|
|
if (int Res = cmpNumbers(L->getOpcode(), R->getOpcode()))
|
|
return Res;
|
|
|
|
if (int Res = cmpNumbers(L->getNumOperands(), R->getNumOperands()))
|
|
return Res;
|
|
|
|
if (int Res = cmpTypes(L->getType(), R->getType()))
|
|
return Res;
|
|
|
|
if (int Res = cmpNumbers(L->getRawSubclassOptionalData(),
|
|
R->getRawSubclassOptionalData()))
|
|
return Res;
|
|
|
|
// We have two instructions of identical opcode and #operands. Check to see
|
|
// if all operands are the same type
|
|
for (unsigned i = 0, e = L->getNumOperands(); i != e; ++i) {
|
|
if (int Res =
|
|
cmpTypes(L->getOperand(i)->getType(), R->getOperand(i)->getType()))
|
|
return Res;
|
|
}
|
|
|
|
// Check special state that is a part of some instructions.
|
|
if (const LoadInst *LI = dyn_cast<LoadInst>(L)) {
|
|
if (int Res = cmpNumbers(LI->isVolatile(), cast<LoadInst>(R)->isVolatile()))
|
|
return Res;
|
|
if (int Res =
|
|
cmpNumbers(LI->getAlignment(), cast<LoadInst>(R)->getAlignment()))
|
|
return Res;
|
|
if (int Res =
|
|
cmpNumbers(LI->getOrdering(), cast<LoadInst>(R)->getOrdering()))
|
|
return Res;
|
|
if (int Res =
|
|
cmpNumbers(LI->getSynchScope(), cast<LoadInst>(R)->getSynchScope()))
|
|
return Res;
|
|
return cmpNumbers((uint64_t)LI->getMetadata(LLVMContext::MD_range),
|
|
(uint64_t)cast<LoadInst>(R)->getMetadata(LLVMContext::MD_range));
|
|
}
|
|
if (const StoreInst *SI = dyn_cast<StoreInst>(L)) {
|
|
if (int Res =
|
|
cmpNumbers(SI->isVolatile(), cast<StoreInst>(R)->isVolatile()))
|
|
return Res;
|
|
if (int Res =
|
|
cmpNumbers(SI->getAlignment(), cast<StoreInst>(R)->getAlignment()))
|
|
return Res;
|
|
if (int Res =
|
|
cmpNumbers(SI->getOrdering(), cast<StoreInst>(R)->getOrdering()))
|
|
return Res;
|
|
return cmpNumbers(SI->getSynchScope(), cast<StoreInst>(R)->getSynchScope());
|
|
}
|
|
if (const CmpInst *CI = dyn_cast<CmpInst>(L))
|
|
return cmpNumbers(CI->getPredicate(), cast<CmpInst>(R)->getPredicate());
|
|
if (const CallInst *CI = dyn_cast<CallInst>(L)) {
|
|
if (int Res = cmpNumbers(CI->getCallingConv(),
|
|
cast<CallInst>(R)->getCallingConv()))
|
|
return Res;
|
|
if (int Res =
|
|
cmpAttrs(CI->getAttributes(), cast<CallInst>(R)->getAttributes()))
|
|
return Res;
|
|
return cmpNumbers(
|
|
(uint64_t)CI->getMetadata(LLVMContext::MD_range),
|
|
(uint64_t)cast<CallInst>(R)->getMetadata(LLVMContext::MD_range));
|
|
}
|
|
if (const InvokeInst *CI = dyn_cast<InvokeInst>(L)) {
|
|
if (int Res = cmpNumbers(CI->getCallingConv(),
|
|
cast<InvokeInst>(R)->getCallingConv()))
|
|
return Res;
|
|
if (int Res =
|
|
cmpAttrs(CI->getAttributes(), cast<InvokeInst>(R)->getAttributes()))
|
|
return Res;
|
|
return cmpNumbers(
|
|
(uint64_t)CI->getMetadata(LLVMContext::MD_range),
|
|
(uint64_t)cast<InvokeInst>(R)->getMetadata(LLVMContext::MD_range));
|
|
}
|
|
if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(L)) {
|
|
ArrayRef<unsigned> LIndices = IVI->getIndices();
|
|
ArrayRef<unsigned> RIndices = cast<InsertValueInst>(R)->getIndices();
|
|
if (int Res = cmpNumbers(LIndices.size(), RIndices.size()))
|
|
return Res;
|
|
for (size_t i = 0, e = LIndices.size(); i != e; ++i) {
|
|
if (int Res = cmpNumbers(LIndices[i], RIndices[i]))
|
|
return Res;
|
|
}
|
|
}
|
|
if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(L)) {
|
|
ArrayRef<unsigned> LIndices = EVI->getIndices();
|
|
ArrayRef<unsigned> RIndices = cast<ExtractValueInst>(R)->getIndices();
|
|
if (int Res = cmpNumbers(LIndices.size(), RIndices.size()))
|
|
return Res;
|
|
for (size_t i = 0, e = LIndices.size(); i != e; ++i) {
|
|
if (int Res = cmpNumbers(LIndices[i], RIndices[i]))
|
|
return Res;
|
|
}
|
|
}
|
|
if (const FenceInst *FI = dyn_cast<FenceInst>(L)) {
|
|
if (int Res =
|
|
cmpNumbers(FI->getOrdering(), cast<FenceInst>(R)->getOrdering()))
|
|
return Res;
|
|
return cmpNumbers(FI->getSynchScope(), cast<FenceInst>(R)->getSynchScope());
|
|
}
|
|
|
|
if (const AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(L)) {
|
|
if (int Res = cmpNumbers(CXI->isVolatile(),
|
|
cast<AtomicCmpXchgInst>(R)->isVolatile()))
|
|
return Res;
|
|
if (int Res = cmpNumbers(CXI->isWeak(),
|
|
cast<AtomicCmpXchgInst>(R)->isWeak()))
|
|
return Res;
|
|
if (int Res = cmpNumbers(CXI->getSuccessOrdering(),
|
|
cast<AtomicCmpXchgInst>(R)->getSuccessOrdering()))
|
|
return Res;
|
|
if (int Res = cmpNumbers(CXI->getFailureOrdering(),
|
|
cast<AtomicCmpXchgInst>(R)->getFailureOrdering()))
|
|
return Res;
|
|
return cmpNumbers(CXI->getSynchScope(),
|
|
cast<AtomicCmpXchgInst>(R)->getSynchScope());
|
|
}
|
|
if (const AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(L)) {
|
|
if (int Res = cmpNumbers(RMWI->getOperation(),
|
|
cast<AtomicRMWInst>(R)->getOperation()))
|
|
return Res;
|
|
if (int Res = cmpNumbers(RMWI->isVolatile(),
|
|
cast<AtomicRMWInst>(R)->isVolatile()))
|
|
return Res;
|
|
if (int Res = cmpNumbers(RMWI->getOrdering(),
|
|
cast<AtomicRMWInst>(R)->getOrdering()))
|
|
return Res;
|
|
return cmpNumbers(RMWI->getSynchScope(),
|
|
cast<AtomicRMWInst>(R)->getSynchScope());
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
// Determine whether two GEP operations perform the same underlying arithmetic.
|
|
// Read method declaration comments for more details.
|
|
int FunctionComparator::cmpGEPs(const GEPOperator *GEPL,
|
|
const GEPOperator *GEPR) {
|
|
|
|
unsigned int ASL = GEPL->getPointerAddressSpace();
|
|
unsigned int ASR = GEPR->getPointerAddressSpace();
|
|
|
|
if (int Res = cmpNumbers(ASL, ASR))
|
|
return Res;
|
|
|
|
// When we have target data, we can reduce the GEP down to the value in bytes
|
|
// added to the address.
|
|
if (DL) {
|
|
unsigned BitWidth = DL->getPointerSizeInBits(ASL);
|
|
APInt OffsetL(BitWidth, 0), OffsetR(BitWidth, 0);
|
|
if (GEPL->accumulateConstantOffset(*DL, OffsetL) &&
|
|
GEPR->accumulateConstantOffset(*DL, OffsetR))
|
|
return cmpAPInts(OffsetL, OffsetR);
|
|
}
|
|
|
|
if (int Res = cmpNumbers((uint64_t)GEPL->getPointerOperand()->getType(),
|
|
(uint64_t)GEPR->getPointerOperand()->getType()))
|
|
return Res;
|
|
|
|
if (int Res = cmpNumbers(GEPL->getNumOperands(), GEPR->getNumOperands()))
|
|
return Res;
|
|
|
|
for (unsigned i = 0, e = GEPL->getNumOperands(); i != e; ++i) {
|
|
if (int Res = cmpValues(GEPL->getOperand(i), GEPR->getOperand(i)))
|
|
return Res;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/// Compare two values used by the two functions under pair-wise comparison. If
|
|
/// this is the first time the values are seen, they're added to the mapping so
|
|
/// that we will detect mismatches on next use.
|
|
/// See comments in declaration for more details.
|
|
int FunctionComparator::cmpValues(const Value *L, const Value *R) {
|
|
// Catch self-reference case.
|
|
if (L == FnL) {
|
|
if (R == FnR)
|
|
return 0;
|
|
return -1;
|
|
}
|
|
if (R == FnR) {
|
|
if (L == FnL)
|
|
return 0;
|
|
return 1;
|
|
}
|
|
|
|
const Constant *ConstL = dyn_cast<Constant>(L);
|
|
const Constant *ConstR = dyn_cast<Constant>(R);
|
|
if (ConstL && ConstR) {
|
|
if (L == R)
|
|
return 0;
|
|
return cmpConstants(ConstL, ConstR);
|
|
}
|
|
|
|
if (ConstL)
|
|
return 1;
|
|
if (ConstR)
|
|
return -1;
|
|
|
|
const InlineAsm *InlineAsmL = dyn_cast<InlineAsm>(L);
|
|
const InlineAsm *InlineAsmR = dyn_cast<InlineAsm>(R);
|
|
|
|
if (InlineAsmL && InlineAsmR)
|
|
return cmpNumbers((uint64_t)L, (uint64_t)R);
|
|
if (InlineAsmL)
|
|
return 1;
|
|
if (InlineAsmR)
|
|
return -1;
|
|
|
|
auto LeftSN = sn_mapL.insert(std::make_pair(L, sn_mapL.size())),
|
|
RightSN = sn_mapR.insert(std::make_pair(R, sn_mapR.size()));
|
|
|
|
return cmpNumbers(LeftSN.first->second, RightSN.first->second);
|
|
}
|
|
// Test whether two basic blocks have equivalent behaviour.
|
|
int FunctionComparator::compare(const BasicBlock *BBL, const BasicBlock *BBR) {
|
|
BasicBlock::const_iterator InstL = BBL->begin(), InstLE = BBL->end();
|
|
BasicBlock::const_iterator InstR = BBR->begin(), InstRE = BBR->end();
|
|
|
|
do {
|
|
if (int Res = cmpValues(InstL, InstR))
|
|
return Res;
|
|
|
|
const GetElementPtrInst *GEPL = dyn_cast<GetElementPtrInst>(InstL);
|
|
const GetElementPtrInst *GEPR = dyn_cast<GetElementPtrInst>(InstR);
|
|
|
|
if (GEPL && !GEPR)
|
|
return 1;
|
|
if (GEPR && !GEPL)
|
|
return -1;
|
|
|
|
if (GEPL && GEPR) {
|
|
if (int Res =
|
|
cmpValues(GEPL->getPointerOperand(), GEPR->getPointerOperand()))
|
|
return Res;
|
|
if (int Res = cmpGEPs(GEPL, GEPR))
|
|
return Res;
|
|
} else {
|
|
if (int Res = cmpOperations(InstL, InstR))
|
|
return Res;
|
|
assert(InstL->getNumOperands() == InstR->getNumOperands());
|
|
|
|
for (unsigned i = 0, e = InstL->getNumOperands(); i != e; ++i) {
|
|
Value *OpL = InstL->getOperand(i);
|
|
Value *OpR = InstR->getOperand(i);
|
|
if (int Res = cmpValues(OpL, OpR))
|
|
return Res;
|
|
if (int Res = cmpNumbers(OpL->getValueID(), OpR->getValueID()))
|
|
return Res;
|
|
// TODO: Already checked in cmpOperation
|
|
if (int Res = cmpTypes(OpL->getType(), OpR->getType()))
|
|
return Res;
|
|
}
|
|
}
|
|
|
|
++InstL, ++InstR;
|
|
} while (InstL != InstLE && InstR != InstRE);
|
|
|
|
if (InstL != InstLE && InstR == InstRE)
|
|
return 1;
|
|
if (InstL == InstLE && InstR != InstRE)
|
|
return -1;
|
|
return 0;
|
|
}
|
|
|
|
// Test whether the two functions have equivalent behaviour.
|
|
int FunctionComparator::compare() {
|
|
|
|
sn_mapL.clear();
|
|
sn_mapR.clear();
|
|
|
|
if (int Res = cmpAttrs(FnL->getAttributes(), FnR->getAttributes()))
|
|
return Res;
|
|
|
|
if (int Res = cmpNumbers(FnL->hasGC(), FnR->hasGC()))
|
|
return Res;
|
|
|
|
if (FnL->hasGC()) {
|
|
if (int Res = cmpNumbers((uint64_t)FnL->getGC(), (uint64_t)FnR->getGC()))
|
|
return Res;
|
|
}
|
|
|
|
if (int Res = cmpNumbers(FnL->hasSection(), FnR->hasSection()))
|
|
return Res;
|
|
|
|
if (FnL->hasSection()) {
|
|
if (int Res = cmpStrings(FnL->getSection(), FnR->getSection()))
|
|
return Res;
|
|
}
|
|
|
|
if (int Res = cmpNumbers(FnL->isVarArg(), FnR->isVarArg()))
|
|
return Res;
|
|
|
|
// TODO: if it's internal and only used in direct calls, we could handle this
|
|
// case too.
|
|
if (int Res = cmpNumbers(FnL->getCallingConv(), FnR->getCallingConv()))
|
|
return Res;
|
|
|
|
if (int Res = cmpTypes(FnL->getFunctionType(), FnR->getFunctionType()))
|
|
return Res;
|
|
|
|
assert(FnL->arg_size() == FnR->arg_size() &&
|
|
"Identically typed functions have different numbers of args!");
|
|
|
|
// Visit the arguments so that they get enumerated in the order they're
|
|
// passed in.
|
|
for (Function::const_arg_iterator ArgLI = FnL->arg_begin(),
|
|
ArgRI = FnR->arg_begin(),
|
|
ArgLE = FnL->arg_end();
|
|
ArgLI != ArgLE; ++ArgLI, ++ArgRI) {
|
|
if (cmpValues(ArgLI, ArgRI) != 0)
|
|
llvm_unreachable("Arguments repeat!");
|
|
}
|
|
|
|
// We do a CFG-ordered walk since the actual ordering of the blocks in the
|
|
// linked list is immaterial. Our walk starts at the entry block for both
|
|
// functions, then takes each block from each terminator in order. As an
|
|
// artifact, this also means that unreachable blocks are ignored.
|
|
SmallVector<const BasicBlock *, 8> FnLBBs, FnRBBs;
|
|
SmallSet<const BasicBlock *, 128> VisitedBBs; // in terms of F1.
|
|
|
|
FnLBBs.push_back(&FnL->getEntryBlock());
|
|
FnRBBs.push_back(&FnR->getEntryBlock());
|
|
|
|
VisitedBBs.insert(FnLBBs[0]);
|
|
while (!FnLBBs.empty()) {
|
|
const BasicBlock *BBL = FnLBBs.pop_back_val();
|
|
const BasicBlock *BBR = FnRBBs.pop_back_val();
|
|
|
|
if (int Res = cmpValues(BBL, BBR))
|
|
return Res;
|
|
|
|
if (int Res = compare(BBL, BBR))
|
|
return Res;
|
|
|
|
const TerminatorInst *TermL = BBL->getTerminator();
|
|
const TerminatorInst *TermR = BBR->getTerminator();
|
|
|
|
assert(TermL->getNumSuccessors() == TermR->getNumSuccessors());
|
|
for (unsigned i = 0, e = TermL->getNumSuccessors(); i != e; ++i) {
|
|
if (!VisitedBBs.insert(TermL->getSuccessor(i)).second)
|
|
continue;
|
|
|
|
FnLBBs.push_back(TermL->getSuccessor(i));
|
|
FnRBBs.push_back(TermR->getSuccessor(i));
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
namespace {
|
|
|
|
/// MergeFunctions finds functions which will generate identical machine code,
|
|
/// by considering all pointer types to be equivalent. Once identified,
|
|
/// MergeFunctions will fold them by replacing a call to one to a call to a
|
|
/// bitcast of the other.
|
|
///
|
|
class MergeFunctions : public ModulePass {
|
|
public:
|
|
static char ID;
|
|
MergeFunctions()
|
|
: ModulePass(ID), HasGlobalAliases(false) {
|
|
initializeMergeFunctionsPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
bool runOnModule(Module &M) override;
|
|
|
|
private:
|
|
typedef std::set<FunctionNode> FnTreeType;
|
|
|
|
/// A work queue of functions that may have been modified and should be
|
|
/// analyzed again.
|
|
std::vector<WeakVH> Deferred;
|
|
|
|
/// Checks the rules of order relation introduced among functions set.
|
|
/// Returns true, if sanity check has been passed, and false if failed.
|
|
bool doSanityCheck(std::vector<WeakVH> &Worklist);
|
|
|
|
/// Insert a ComparableFunction into the FnTree, or merge it away if it's
|
|
/// equal to one that's already present.
|
|
bool insert(Function *NewFunction);
|
|
|
|
/// Remove a Function from the FnTree and queue it up for a second sweep of
|
|
/// analysis.
|
|
void remove(Function *F);
|
|
|
|
/// Find the functions that use this Value and remove them from FnTree and
|
|
/// queue the functions.
|
|
void removeUsers(Value *V);
|
|
|
|
/// Replace all direct calls of Old with calls of New. Will bitcast New if
|
|
/// necessary to make types match.
|
|
void replaceDirectCallers(Function *Old, Function *New);
|
|
|
|
/// Merge two equivalent functions. Upon completion, G may be deleted, or may
|
|
/// be converted into a thunk. In either case, it should never be visited
|
|
/// again.
|
|
void mergeTwoFunctions(Function *F, Function *G);
|
|
|
|
/// Replace G with a thunk or an alias to F. Deletes G.
|
|
void writeThunkOrAlias(Function *F, Function *G);
|
|
|
|
/// Replace G with a simple tail call to bitcast(F). Also replace direct uses
|
|
/// of G with bitcast(F). Deletes G.
|
|
void writeThunk(Function *F, Function *G);
|
|
|
|
/// Replace G with an alias to F. Deletes G.
|
|
void writeAlias(Function *F, Function *G);
|
|
|
|
/// The set of all distinct functions. Use the insert() and remove() methods
|
|
/// to modify it.
|
|
FnTreeType FnTree;
|
|
|
|
/// DataLayout for more accurate GEP comparisons. May be NULL.
|
|
const DataLayout *DL;
|
|
|
|
/// Whether or not the target supports global aliases.
|
|
bool HasGlobalAliases;
|
|
};
|
|
|
|
} // end anonymous namespace
|
|
|
|
char MergeFunctions::ID = 0;
|
|
INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false)
|
|
|
|
ModulePass *llvm::createMergeFunctionsPass() {
|
|
return new MergeFunctions();
|
|
}
|
|
|
|
bool MergeFunctions::doSanityCheck(std::vector<WeakVH> &Worklist) {
|
|
if (const unsigned Max = NumFunctionsForSanityCheck) {
|
|
unsigned TripleNumber = 0;
|
|
bool Valid = true;
|
|
|
|
dbgs() << "MERGEFUNC-SANITY: Started for first " << Max << " functions.\n";
|
|
|
|
unsigned i = 0;
|
|
for (std::vector<WeakVH>::iterator I = Worklist.begin(), E = Worklist.end();
|
|
I != E && i < Max; ++I, ++i) {
|
|
unsigned j = i;
|
|
for (std::vector<WeakVH>::iterator J = I; J != E && j < Max; ++J, ++j) {
|
|
Function *F1 = cast<Function>(*I);
|
|
Function *F2 = cast<Function>(*J);
|
|
int Res1 = FunctionComparator(DL, F1, F2).compare();
|
|
int Res2 = FunctionComparator(DL, F2, F1).compare();
|
|
|
|
// If F1 <= F2, then F2 >= F1, otherwise report failure.
|
|
if (Res1 != -Res2) {
|
|
dbgs() << "MERGEFUNC-SANITY: Non-symmetric; triple: " << TripleNumber
|
|
<< "\n";
|
|
F1->dump();
|
|
F2->dump();
|
|
Valid = false;
|
|
}
|
|
|
|
if (Res1 == 0)
|
|
continue;
|
|
|
|
unsigned k = j;
|
|
for (std::vector<WeakVH>::iterator K = J; K != E && k < Max;
|
|
++k, ++K, ++TripleNumber) {
|
|
if (K == J)
|
|
continue;
|
|
|
|
Function *F3 = cast<Function>(*K);
|
|
int Res3 = FunctionComparator(DL, F1, F3).compare();
|
|
int Res4 = FunctionComparator(DL, F2, F3).compare();
|
|
|
|
bool Transitive = true;
|
|
|
|
if (Res1 != 0 && Res1 == Res4) {
|
|
// F1 > F2, F2 > F3 => F1 > F3
|
|
Transitive = Res3 == Res1;
|
|
} else if (Res3 != 0 && Res3 == -Res4) {
|
|
// F1 > F3, F3 > F2 => F1 > F2
|
|
Transitive = Res3 == Res1;
|
|
} else if (Res4 != 0 && -Res3 == Res4) {
|
|
// F2 > F3, F3 > F1 => F2 > F1
|
|
Transitive = Res4 == -Res1;
|
|
}
|
|
|
|
if (!Transitive) {
|
|
dbgs() << "MERGEFUNC-SANITY: Non-transitive; triple: "
|
|
<< TripleNumber << "\n";
|
|
dbgs() << "Res1, Res3, Res4: " << Res1 << ", " << Res3 << ", "
|
|
<< Res4 << "\n";
|
|
F1->dump();
|
|
F2->dump();
|
|
F3->dump();
|
|
Valid = false;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
dbgs() << "MERGEFUNC-SANITY: " << (Valid ? "Passed." : "Failed.") << "\n";
|
|
return Valid;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
bool MergeFunctions::runOnModule(Module &M) {
|
|
bool Changed = false;
|
|
DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
|
|
DL = DLP ? &DLP->getDataLayout() : nullptr;
|
|
|
|
for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
|
|
if (!I->isDeclaration() && !I->hasAvailableExternallyLinkage())
|
|
Deferred.push_back(WeakVH(I));
|
|
}
|
|
|
|
do {
|
|
std::vector<WeakVH> Worklist;
|
|
Deferred.swap(Worklist);
|
|
|
|
DEBUG(doSanityCheck(Worklist));
|
|
|
|
DEBUG(dbgs() << "size of module: " << M.size() << '\n');
|
|
DEBUG(dbgs() << "size of worklist: " << Worklist.size() << '\n');
|
|
|
|
// Insert only strong functions and merge them. Strong function merging
|
|
// always deletes one of them.
|
|
for (std::vector<WeakVH>::iterator I = Worklist.begin(),
|
|
E = Worklist.end(); I != E; ++I) {
|
|
if (!*I) continue;
|
|
Function *F = cast<Function>(*I);
|
|
if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
|
|
!F->mayBeOverridden()) {
|
|
Changed |= insert(F);
|
|
}
|
|
}
|
|
|
|
// Insert only weak functions and merge them. By doing these second we
|
|
// create thunks to the strong function when possible. When two weak
|
|
// functions are identical, we create a new strong function with two weak
|
|
// weak thunks to it which are identical but not mergable.
|
|
for (std::vector<WeakVH>::iterator I = Worklist.begin(),
|
|
E = Worklist.end(); I != E; ++I) {
|
|
if (!*I) continue;
|
|
Function *F = cast<Function>(*I);
|
|
if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
|
|
F->mayBeOverridden()) {
|
|
Changed |= insert(F);
|
|
}
|
|
}
|
|
DEBUG(dbgs() << "size of FnTree: " << FnTree.size() << '\n');
|
|
} while (!Deferred.empty());
|
|
|
|
FnTree.clear();
|
|
|
|
return Changed;
|
|
}
|
|
|
|
// Replace direct callers of Old with New.
|
|
void MergeFunctions::replaceDirectCallers(Function *Old, Function *New) {
|
|
Constant *BitcastNew = ConstantExpr::getBitCast(New, Old->getType());
|
|
for (auto UI = Old->use_begin(), UE = Old->use_end(); UI != UE;) {
|
|
Use *U = &*UI;
|
|
++UI;
|
|
CallSite CS(U->getUser());
|
|
if (CS && CS.isCallee(U)) {
|
|
remove(CS.getInstruction()->getParent()->getParent());
|
|
U->set(BitcastNew);
|
|
}
|
|
}
|
|
}
|
|
|
|
// Replace G with an alias to F if possible, or else a thunk to F. Deletes G.
|
|
void MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
|
|
if (HasGlobalAliases && G->hasUnnamedAddr()) {
|
|
if (G->hasExternalLinkage() || G->hasLocalLinkage() ||
|
|
G->hasWeakLinkage()) {
|
|
writeAlias(F, G);
|
|
return;
|
|
}
|
|
}
|
|
|
|
writeThunk(F, G);
|
|
}
|
|
|
|
// Helper for writeThunk,
|
|
// Selects proper bitcast operation,
|
|
// but a bit simpler then CastInst::getCastOpcode.
|
|
static Value *createCast(IRBuilder<false> &Builder, Value *V, Type *DestTy) {
|
|
Type *SrcTy = V->getType();
|
|
if (SrcTy->isStructTy()) {
|
|
assert(DestTy->isStructTy());
|
|
assert(SrcTy->getStructNumElements() == DestTy->getStructNumElements());
|
|
Value *Result = UndefValue::get(DestTy);
|
|
for (unsigned int I = 0, E = SrcTy->getStructNumElements(); I < E; ++I) {
|
|
Value *Element = createCast(
|
|
Builder, Builder.CreateExtractValue(V, makeArrayRef(I)),
|
|
DestTy->getStructElementType(I));
|
|
|
|
Result =
|
|
Builder.CreateInsertValue(Result, Element, makeArrayRef(I));
|
|
}
|
|
return Result;
|
|
}
|
|
assert(!DestTy->isStructTy());
|
|
if (SrcTy->isIntegerTy() && DestTy->isPointerTy())
|
|
return Builder.CreateIntToPtr(V, DestTy);
|
|
else if (SrcTy->isPointerTy() && DestTy->isIntegerTy())
|
|
return Builder.CreatePtrToInt(V, DestTy);
|
|
else
|
|
return Builder.CreateBitCast(V, DestTy);
|
|
}
|
|
|
|
// Replace G with a simple tail call to bitcast(F). Also replace direct uses
|
|
// of G with bitcast(F). Deletes G.
|
|
void MergeFunctions::writeThunk(Function *F, Function *G) {
|
|
if (!G->mayBeOverridden()) {
|
|
// Redirect direct callers of G to F.
|
|
replaceDirectCallers(G, F);
|
|
}
|
|
|
|
// If G was internal then we may have replaced all uses of G with F. If so,
|
|
// stop here and delete G. There's no need for a thunk.
|
|
if (G->hasLocalLinkage() && G->use_empty()) {
|
|
G->eraseFromParent();
|
|
return;
|
|
}
|
|
|
|
Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "",
|
|
G->getParent());
|
|
BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG);
|
|
IRBuilder<false> Builder(BB);
|
|
|
|
SmallVector<Value *, 16> Args;
|
|
unsigned i = 0;
|
|
FunctionType *FFTy = F->getFunctionType();
|
|
for (Function::arg_iterator AI = NewG->arg_begin(), AE = NewG->arg_end();
|
|
AI != AE; ++AI) {
|
|
Args.push_back(createCast(Builder, (Value*)AI, FFTy->getParamType(i)));
|
|
++i;
|
|
}
|
|
|
|
CallInst *CI = Builder.CreateCall(F, Args);
|
|
CI->setTailCall();
|
|
CI->setCallingConv(F->getCallingConv());
|
|
if (NewG->getReturnType()->isVoidTy()) {
|
|
Builder.CreateRetVoid();
|
|
} else {
|
|
Builder.CreateRet(createCast(Builder, CI, NewG->getReturnType()));
|
|
}
|
|
|
|
NewG->copyAttributesFrom(G);
|
|
NewG->takeName(G);
|
|
removeUsers(G);
|
|
G->replaceAllUsesWith(NewG);
|
|
G->eraseFromParent();
|
|
|
|
DEBUG(dbgs() << "writeThunk: " << NewG->getName() << '\n');
|
|
++NumThunksWritten;
|
|
}
|
|
|
|
// Replace G with an alias to F and delete G.
|
|
void MergeFunctions::writeAlias(Function *F, Function *G) {
|
|
PointerType *PTy = G->getType();
|
|
auto *GA = GlobalAlias::create(PTy->getElementType(), PTy->getAddressSpace(),
|
|
G->getLinkage(), "", F);
|
|
F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
|
|
GA->takeName(G);
|
|
GA->setVisibility(G->getVisibility());
|
|
removeUsers(G);
|
|
G->replaceAllUsesWith(GA);
|
|
G->eraseFromParent();
|
|
|
|
DEBUG(dbgs() << "writeAlias: " << GA->getName() << '\n');
|
|
++NumAliasesWritten;
|
|
}
|
|
|
|
// Merge two equivalent functions. Upon completion, Function G is deleted.
|
|
void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
|
|
if (F->mayBeOverridden()) {
|
|
assert(G->mayBeOverridden());
|
|
|
|
if (HasGlobalAliases) {
|
|
// Make them both thunks to the same internal function.
|
|
Function *H = Function::Create(F->getFunctionType(), F->getLinkage(), "",
|
|
F->getParent());
|
|
H->copyAttributesFrom(F);
|
|
H->takeName(F);
|
|
removeUsers(F);
|
|
F->replaceAllUsesWith(H);
|
|
|
|
unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment());
|
|
|
|
writeAlias(F, G);
|
|
writeAlias(F, H);
|
|
|
|
F->setAlignment(MaxAlignment);
|
|
F->setLinkage(GlobalValue::PrivateLinkage);
|
|
} else {
|
|
// We can't merge them. Instead, pick one and update all direct callers
|
|
// to call it and hope that we improve the instruction cache hit rate.
|
|
replaceDirectCallers(G, F);
|
|
}
|
|
|
|
++NumDoubleWeak;
|
|
} else {
|
|
writeThunkOrAlias(F, G);
|
|
}
|
|
|
|
++NumFunctionsMerged;
|
|
}
|
|
|
|
// Insert a ComparableFunction into the FnTree, or merge it away if equal to one
|
|
// that was already inserted.
|
|
bool MergeFunctions::insert(Function *NewFunction) {
|
|
std::pair<FnTreeType::iterator, bool> Result =
|
|
FnTree.insert(FunctionNode(NewFunction, DL));
|
|
|
|
if (Result.second) {
|
|
DEBUG(dbgs() << "Inserting as unique: " << NewFunction->getName() << '\n');
|
|
return false;
|
|
}
|
|
|
|
const FunctionNode &OldF = *Result.first;
|
|
|
|
// Don't merge tiny functions, since it can just end up making the function
|
|
// larger.
|
|
// FIXME: Should still merge them if they are unnamed_addr and produce an
|
|
// alias.
|
|
if (NewFunction->size() == 1) {
|
|
if (NewFunction->front().size() <= 2) {
|
|
DEBUG(dbgs() << NewFunction->getName()
|
|
<< " is to small to bother merging\n");
|
|
return false;
|
|
}
|
|
}
|
|
|
|
// Never thunk a strong function to a weak function.
|
|
assert(!OldF.getFunc()->mayBeOverridden() || NewFunction->mayBeOverridden());
|
|
|
|
DEBUG(dbgs() << " " << OldF.getFunc()->getName()
|
|
<< " == " << NewFunction->getName() << '\n');
|
|
|
|
Function *DeleteF = NewFunction;
|
|
mergeTwoFunctions(OldF.getFunc(), DeleteF);
|
|
return true;
|
|
}
|
|
|
|
// Remove a function from FnTree. If it was already in FnTree, add
|
|
// it to Deferred so that we'll look at it in the next round.
|
|
void MergeFunctions::remove(Function *F) {
|
|
// We need to make sure we remove F, not a function "equal" to F per the
|
|
// function equality comparator.
|
|
FnTreeType::iterator found = FnTree.find(FunctionNode(F, DL));
|
|
size_t Erased = 0;
|
|
if (found != FnTree.end() && found->getFunc() == F) {
|
|
Erased = 1;
|
|
FnTree.erase(found);
|
|
}
|
|
|
|
if (Erased) {
|
|
DEBUG(dbgs() << "Removed " << F->getName()
|
|
<< " from set and deferred it.\n");
|
|
Deferred.push_back(F);
|
|
}
|
|
}
|
|
|
|
// For each instruction used by the value, remove() the function that contains
|
|
// the instruction. This should happen right before a call to RAUW.
|
|
void MergeFunctions::removeUsers(Value *V) {
|
|
std::vector<Value *> Worklist;
|
|
Worklist.push_back(V);
|
|
while (!Worklist.empty()) {
|
|
Value *V = Worklist.back();
|
|
Worklist.pop_back();
|
|
|
|
for (User *U : V->users()) {
|
|
if (Instruction *I = dyn_cast<Instruction>(U)) {
|
|
remove(I->getParent()->getParent());
|
|
} else if (isa<GlobalValue>(U)) {
|
|
// do nothing
|
|
} else if (Constant *C = dyn_cast<Constant>(U)) {
|
|
for (User *UU : C->users())
|
|
Worklist.push_back(UU);
|
|
}
|
|
}
|
|
}
|
|
}
|