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IRCE eliminates range checks of the form 0 <= A * I + B < Length by splitting a loop's iteration space into three segments in a way that the check is completely redundant in the middle segment. As an example, IRCE will convert len = < known positive > for (i = 0; i < n; i++) { if (0 <= i && i < len) { do_something(); } else { throw_out_of_bounds(); } } to len = < known positive > limit = smin(n, len) // no first segment for (i = 0; i < limit; i++) { if (0 <= i && i < len) { // this check is fully redundant do_something(); } else { throw_out_of_bounds(); } } for (i = limit; i < n; i++) { if (0 <= i && i < len) { do_something(); } else { throw_out_of_bounds(); } } IRCE can deal with multiple range checks in the same loop (it takes the intersection of the ranges that will make each of them redundant individually). Currently IRCE does not do any profitability analysis. That is a TODO. Please note that the status of this pass is *experimental*, and it is not part of any default pass pipeline. Having said that, I will love to get feedback and general input from people interested in trying this out. This pass was originally r226201. It was reverted because it used C++ features not supported by MSVC 2012. Differential Revision: http://reviews.llvm.org/D6693 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226238 91177308-0d34-0410-b5e6-96231b3b80d8
418 lines
14 KiB
C++
418 lines
14 KiB
C++
//===-- Scalar.h - Scalar Transformations -----------------------*- C++ -*-===//
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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 header file defines prototypes for accessor functions that expose passes
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// in the Scalar transformations library.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_TRANSFORMS_SCALAR_H
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#define LLVM_TRANSFORMS_SCALAR_H
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#include "llvm/ADT/StringRef.h"
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namespace llvm {
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class BasicBlockPass;
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class FunctionPass;
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class Pass;
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class GetElementPtrInst;
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class PassInfo;
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class TerminatorInst;
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class TargetLowering;
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class TargetMachine;
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//===----------------------------------------------------------------------===//
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//
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// ConstantPropagation - A worklist driven constant propagation pass
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//
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FunctionPass *createConstantPropagationPass();
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//===----------------------------------------------------------------------===//
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//
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// AlignmentFromAssumptions - Use assume intrinsics to set load/store
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// alignments.
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//
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FunctionPass *createAlignmentFromAssumptionsPass();
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//===----------------------------------------------------------------------===//
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//
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// SCCP - Sparse conditional constant propagation.
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//
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FunctionPass *createSCCPPass();
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//===----------------------------------------------------------------------===//
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//
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// DeadInstElimination - This pass quickly removes trivially dead instructions
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// without modifying the CFG of the function. It is a BasicBlockPass, so it
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// runs efficiently when queued next to other BasicBlockPass's.
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//
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Pass *createDeadInstEliminationPass();
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//===----------------------------------------------------------------------===//
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//
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// DeadCodeElimination - This pass is more powerful than DeadInstElimination,
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// because it is worklist driven that can potentially revisit instructions when
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// their other instructions become dead, to eliminate chains of dead
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// computations.
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//
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FunctionPass *createDeadCodeEliminationPass();
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//===----------------------------------------------------------------------===//
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//
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// DeadStoreElimination - This pass deletes stores that are post-dominated by
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// must-aliased stores and are not loaded used between the stores.
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//
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FunctionPass *createDeadStoreEliminationPass();
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//===----------------------------------------------------------------------===//
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//
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// AggressiveDCE - This pass uses the SSA based Aggressive DCE algorithm. This
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// algorithm assumes instructions are dead until proven otherwise, which makes
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// it more successful are removing non-obviously dead instructions.
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//
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FunctionPass *createAggressiveDCEPass();
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//===----------------------------------------------------------------------===//
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//
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// SROA - Replace aggregates or pieces of aggregates with scalar SSA values.
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//
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FunctionPass *createSROAPass(bool RequiresDomTree = true);
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//===----------------------------------------------------------------------===//
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//
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// ScalarReplAggregates - Break up alloca's of aggregates into multiple allocas
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// if possible.
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//
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FunctionPass *createScalarReplAggregatesPass(signed Threshold = -1,
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bool UseDomTree = true,
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signed StructMemberThreshold = -1,
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signed ArrayElementThreshold = -1,
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signed ScalarLoadThreshold = -1);
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//===----------------------------------------------------------------------===//
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//
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// InductiveRangeCheckElimination - Transform loops to elide range checks on
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// linear functions of the induction variable.
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//
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Pass *createInductiveRangeCheckEliminationPass();
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//===----------------------------------------------------------------------===//
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//
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// InductionVariableSimplify - Transform induction variables in a program to all
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// use a single canonical induction variable per loop.
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//
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Pass *createIndVarSimplifyPass();
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//===----------------------------------------------------------------------===//
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//
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// InstructionCombining - Combine instructions to form fewer, simple
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// instructions. This pass does not modify the CFG, and has a tendency to make
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// instructions dead, so a subsequent DCE pass is useful.
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//
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// This pass combines things like:
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// %Y = add int 1, %X
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// %Z = add int 1, %Y
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// into:
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// %Z = add int 2, %X
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//
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FunctionPass *createInstructionCombiningPass();
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//===----------------------------------------------------------------------===//
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//
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// LICM - This pass is a loop invariant code motion and memory promotion pass.
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//
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Pass *createLICMPass();
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//===----------------------------------------------------------------------===//
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//
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// LoopStrengthReduce - This pass is strength reduces GEP instructions that use
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// a loop's canonical induction variable as one of their indices.
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//
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Pass *createLoopStrengthReducePass();
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Pass *createGlobalMergePass(const TargetMachine *TM = nullptr);
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//===----------------------------------------------------------------------===//
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//
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// LoopUnswitch - This pass is a simple loop unswitching pass.
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//
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Pass *createLoopUnswitchPass(bool OptimizeForSize = false);
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//===----------------------------------------------------------------------===//
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//
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// LoopInstSimplify - This pass simplifies instructions in a loop's body.
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//
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Pass *createLoopInstSimplifyPass();
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//===----------------------------------------------------------------------===//
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//
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// LoopUnroll - This pass is a simple loop unrolling pass.
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//
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Pass *createLoopUnrollPass(int Threshold = -1, int Count = -1,
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int AllowPartial = -1, int Runtime = -1);
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// Create an unrolling pass for full unrolling only.
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Pass *createSimpleLoopUnrollPass();
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//===----------------------------------------------------------------------===//
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//
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// LoopReroll - This pass is a simple loop rerolling pass.
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//
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Pass *createLoopRerollPass();
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//===----------------------------------------------------------------------===//
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//
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// LoopRotate - This pass is a simple loop rotating pass.
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//
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Pass *createLoopRotatePass(int MaxHeaderSize = -1);
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//===----------------------------------------------------------------------===//
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//
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// LoopIdiom - This pass recognizes and replaces idioms in loops.
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//
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Pass *createLoopIdiomPass();
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//===----------------------------------------------------------------------===//
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//
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// PromoteMemoryToRegister - This pass is used to promote memory references to
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// be register references. A simple example of the transformation performed by
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// this pass is:
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//
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// FROM CODE TO CODE
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// %X = alloca i32, i32 1 ret i32 42
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// store i32 42, i32 *%X
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// %Y = load i32* %X
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// ret i32 %Y
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//
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FunctionPass *createPromoteMemoryToRegisterPass();
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//===----------------------------------------------------------------------===//
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//
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// DemoteRegisterToMemoryPass - This pass is used to demote registers to memory
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// references. In basically undoes the PromoteMemoryToRegister pass to make cfg
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// hacking easier.
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//
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FunctionPass *createDemoteRegisterToMemoryPass();
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extern char &DemoteRegisterToMemoryID;
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//===----------------------------------------------------------------------===//
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//
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// Reassociate - This pass reassociates commutative expressions in an order that
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// is designed to promote better constant propagation, GCSE, LICM, PRE...
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//
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// For example: 4 + (x + 5) -> x + (4 + 5)
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//
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FunctionPass *createReassociatePass();
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//===----------------------------------------------------------------------===//
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//
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// JumpThreading - Thread control through mult-pred/multi-succ blocks where some
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// preds always go to some succ. Thresholds other than minus one override the
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// internal BB duplication default threshold.
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//
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FunctionPass *createJumpThreadingPass(int Threshold = -1);
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//===----------------------------------------------------------------------===//
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//
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// CFGSimplification - Merge basic blocks, eliminate unreachable blocks,
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// simplify terminator instructions, etc...
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//
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FunctionPass *createCFGSimplificationPass(int Threshold = -1);
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//===----------------------------------------------------------------------===//
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//
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// FlattenCFG - flatten CFG, reduce number of conditional branches by using
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// parallel-and and parallel-or mode, etc...
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//
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FunctionPass *createFlattenCFGPass();
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//===----------------------------------------------------------------------===//
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//
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// CFG Structurization - Remove irreducible control flow
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//
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Pass *createStructurizeCFGPass();
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//===----------------------------------------------------------------------===//
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//
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// BreakCriticalEdges - Break all of the critical edges in the CFG by inserting
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// a dummy basic block. This pass may be "required" by passes that cannot deal
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// with critical edges. For this usage, a pass must call:
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//
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// AU.addRequiredID(BreakCriticalEdgesID);
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//
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// This pass obviously invalidates the CFG, but can update forward dominator
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// (set, immediate dominators, tree, and frontier) information.
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//
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FunctionPass *createBreakCriticalEdgesPass();
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extern char &BreakCriticalEdgesID;
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//===----------------------------------------------------------------------===//
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//
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// LoopSimplify - Insert Pre-header blocks into the CFG for every function in
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// the module. This pass updates dominator information, loop information, and
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// does not add critical edges to the CFG.
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//
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// AU.addRequiredID(LoopSimplifyID);
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//
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Pass *createLoopSimplifyPass();
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extern char &LoopSimplifyID;
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//===----------------------------------------------------------------------===//
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//
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// TailCallElimination - This pass eliminates call instructions to the current
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// function which occur immediately before return instructions.
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//
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FunctionPass *createTailCallEliminationPass();
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//===----------------------------------------------------------------------===//
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//
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// LowerSwitch - This pass converts SwitchInst instructions into a sequence of
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// chained binary branch instructions.
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//
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FunctionPass *createLowerSwitchPass();
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extern char &LowerSwitchID;
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//===----------------------------------------------------------------------===//
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//
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// LowerInvoke - This pass removes invoke instructions, converting them to call
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// instructions.
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//
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FunctionPass *createLowerInvokePass();
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extern char &LowerInvokePassID;
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//===----------------------------------------------------------------------===//
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//
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// LCSSA - This pass inserts phi nodes at loop boundaries to simplify other loop
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// optimizations.
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//
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Pass *createLCSSAPass();
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extern char &LCSSAID;
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//===----------------------------------------------------------------------===//
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//
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// EarlyCSE - This pass performs a simple and fast CSE pass over the dominator
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// tree.
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//
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FunctionPass *createEarlyCSEPass();
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//===----------------------------------------------------------------------===//
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//
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// MergedLoadStoreMotion - This pass merges loads and stores in diamonds. Loads
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// are hoisted into the header, while stores sink into the footer.
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//
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FunctionPass *createMergedLoadStoreMotionPass();
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//===----------------------------------------------------------------------===//
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//
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// GVN - This pass performs global value numbering and redundant load
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// elimination cotemporaneously.
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//
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FunctionPass *createGVNPass(bool NoLoads = false);
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//===----------------------------------------------------------------------===//
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//
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// MemCpyOpt - This pass performs optimizations related to eliminating memcpy
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// calls and/or combining multiple stores into memset's.
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//
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FunctionPass *createMemCpyOptPass();
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//===----------------------------------------------------------------------===//
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//
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// LoopDeletion - This pass performs DCE of non-infinite loops that it
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// can prove are dead.
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//
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Pass *createLoopDeletionPass();
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//===----------------------------------------------------------------------===//
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//
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// ConstantHoisting - This pass prepares a function for expensive constants.
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//
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FunctionPass *createConstantHoistingPass();
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//===----------------------------------------------------------------------===//
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//
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// InstructionNamer - Give any unnamed non-void instructions "tmp" names.
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//
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FunctionPass *createInstructionNamerPass();
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extern char &InstructionNamerID;
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//===----------------------------------------------------------------------===//
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//
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// Sink - Code Sinking
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//
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FunctionPass *createSinkingPass();
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//===----------------------------------------------------------------------===//
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//
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// LowerAtomic - Lower atomic intrinsics to non-atomic form
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//
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Pass *createLowerAtomicPass();
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//===----------------------------------------------------------------------===//
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//
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// ValuePropagation - Propagate CFG-derived value information
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//
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Pass *createCorrelatedValuePropagationPass();
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//===----------------------------------------------------------------------===//
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//
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// InstructionSimplifier - Remove redundant instructions.
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//
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FunctionPass *createInstructionSimplifierPass();
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extern char &InstructionSimplifierID;
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//===----------------------------------------------------------------------===//
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//
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// LowerExpectIntrinsics - Removes llvm.expect intrinsics and creates
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// "block_weights" metadata.
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FunctionPass *createLowerExpectIntrinsicPass();
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//===----------------------------------------------------------------------===//
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//
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// PartiallyInlineLibCalls - Tries to inline the fast path of library
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// calls such as sqrt.
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//
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FunctionPass *createPartiallyInlineLibCallsPass();
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//===----------------------------------------------------------------------===//
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//
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// SampleProfilePass - Loads sample profile data from disk and generates
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// IR metadata to reflect the profile.
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FunctionPass *createSampleProfileLoaderPass();
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FunctionPass *createSampleProfileLoaderPass(StringRef Name);
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//===----------------------------------------------------------------------===//
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//
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// ScalarizerPass - Converts vector operations into scalar operations
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//
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FunctionPass *createScalarizerPass();
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//===----------------------------------------------------------------------===//
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//
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// AddDiscriminators - Add DWARF path discriminators to the IR.
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FunctionPass *createAddDiscriminatorsPass();
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//===----------------------------------------------------------------------===//
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//
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// SeparateConstOffsetFromGEP - Split GEPs for better CSE
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//
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FunctionPass *
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createSeparateConstOffsetFromGEPPass(const TargetMachine *TM = nullptr,
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bool LowerGEP = false);
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//===----------------------------------------------------------------------===//
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//
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// LoadCombine - Combine loads into bigger loads.
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//
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BasicBlockPass *createLoadCombinePass();
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} // End llvm namespace
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#endif
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