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This requires a number of steps. 1) Move value_use_iterator into the Value class as an implementation detail 2) Change it to actually be a *Use* iterator rather than a *User* iterator. 3) Add an adaptor which is a User iterator that always looks through the Use to the User. 4) Wrap these in Value::use_iterator and Value::user_iterator typedefs. 5) Add the range adaptors as Value::uses() and Value::users(). 6) Update *all* of the callers to correctly distinguish between whether they wanted a use_iterator (and to explicitly dig out the User when needed), or a user_iterator which makes the Use itself totally opaque. Because #6 requires churning essentially everything that walked the Use-Def chains, I went ahead and added all of the range adaptors and switched them to range-based loops where appropriate. Also because the renaming requires at least churning every line of code, it didn't make any sense to split these up into multiple commits -- all of which would touch all of the same lies of code. The result is still not quite optimal. The Value::use_iterator is a nice regular iterator, but Value::user_iterator is an iterator over User*s rather than over the User objects themselves. As a consequence, it fits a bit awkwardly into the range-based world and it has the weird extra-dereferencing 'operator->' that so many of our iterators have. I think this could be fixed by providing something which transforms a range of T&s into a range of T*s, but that *can* be separated into another patch, and it isn't yet 100% clear whether this is the right move. However, this change gets us most of the benefit and cleans up a substantial amount of code around Use and User. =] git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203364 91177308-0d34-0410-b5e6-96231b3b80d8
133 lines
4.5 KiB
C++
133 lines
4.5 KiB
C++
//===- Reg2Mem.cpp - Convert registers to allocas -------------------------===//
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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 file demotes all registers to memory references. It is intended to be
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// the inverse of PromoteMemoryToRegister. By converting to loads, the only
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// values live across basic blocks are allocas and loads before phi nodes.
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// It is intended that this should make CFG hacking much easier.
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// To make later hacking easier, the entry block is split into two, such that
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// all introduced allocas and nothing else are in the entry block.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "reg2mem"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/IR/BasicBlock.h"
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#include "llvm/IR/CFG.h"
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#include "llvm/IR/Function.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/Pass.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include <list>
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using namespace llvm;
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STATISTIC(NumRegsDemoted, "Number of registers demoted");
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STATISTIC(NumPhisDemoted, "Number of phi-nodes demoted");
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namespace {
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struct RegToMem : public FunctionPass {
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static char ID; // Pass identification, replacement for typeid
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RegToMem() : FunctionPass(ID) {
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initializeRegToMemPass(*PassRegistry::getPassRegistry());
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.addRequiredID(BreakCriticalEdgesID);
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AU.addPreservedID(BreakCriticalEdgesID);
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}
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bool valueEscapes(const Instruction *Inst) const {
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const BasicBlock *BB = Inst->getParent();
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for (const User *U : Inst->users()) {
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const Instruction *UI = cast<Instruction>(U);
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if (UI->getParent() != BB || isa<PHINode>(UI))
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return true;
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}
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return false;
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}
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bool runOnFunction(Function &F) override;
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};
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}
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char RegToMem::ID = 0;
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INITIALIZE_PASS_BEGIN(RegToMem, "reg2mem", "Demote all values to stack slots",
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false, false)
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INITIALIZE_PASS_DEPENDENCY(BreakCriticalEdges)
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INITIALIZE_PASS_END(RegToMem, "reg2mem", "Demote all values to stack slots",
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false, false)
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bool RegToMem::runOnFunction(Function &F) {
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if (F.isDeclaration())
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return false;
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// Insert all new allocas into entry block.
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BasicBlock *BBEntry = &F.getEntryBlock();
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assert(pred_begin(BBEntry) == pred_end(BBEntry) &&
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"Entry block to function must not have predecessors!");
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// Find first non-alloca instruction and create insertion point. This is
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// safe if block is well-formed: it always have terminator, otherwise
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// we'll get and assertion.
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BasicBlock::iterator I = BBEntry->begin();
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while (isa<AllocaInst>(I)) ++I;
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CastInst *AllocaInsertionPoint =
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new BitCastInst(Constant::getNullValue(Type::getInt32Ty(F.getContext())),
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Type::getInt32Ty(F.getContext()),
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"reg2mem alloca point", I);
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// Find the escaped instructions. But don't create stack slots for
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// allocas in entry block.
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std::list<Instruction*> WorkList;
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for (Function::iterator ibb = F.begin(), ibe = F.end();
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ibb != ibe; ++ibb)
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for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
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iib != iie; ++iib) {
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if (!(isa<AllocaInst>(iib) && iib->getParent() == BBEntry) &&
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valueEscapes(iib)) {
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WorkList.push_front(&*iib);
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}
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}
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// Demote escaped instructions
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NumRegsDemoted += WorkList.size();
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for (std::list<Instruction*>::iterator ilb = WorkList.begin(),
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ile = WorkList.end(); ilb != ile; ++ilb)
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DemoteRegToStack(**ilb, false, AllocaInsertionPoint);
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WorkList.clear();
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// Find all phi's
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for (Function::iterator ibb = F.begin(), ibe = F.end();
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ibb != ibe; ++ibb)
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for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
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iib != iie; ++iib)
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if (isa<PHINode>(iib))
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WorkList.push_front(&*iib);
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// Demote phi nodes
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NumPhisDemoted += WorkList.size();
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for (std::list<Instruction*>::iterator ilb = WorkList.begin(),
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ile = WorkList.end(); ilb != ile; ++ilb)
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DemotePHIToStack(cast<PHINode>(*ilb), AllocaInsertionPoint);
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return true;
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}
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// createDemoteRegisterToMemory - Provide an entry point to create this pass.
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char &llvm::DemoteRegisterToMemoryID = RegToMem::ID;
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FunctionPass *llvm::createDemoteRegisterToMemoryPass() {
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return new RegToMem();
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}
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