Jingyue Wu 2918efd551 Add straight-line strength reduction to LLVM
Summary:
Straight-line strength reduction (SLSR) is implemented in GCC but not yet in
LLVM. It has proven to effectively simplify statements derived from an unrolled
loop, and can potentially benefit many other cases too. For example,

LLVM unrolls

  #pragma unroll
  foo (int i = 0; i < 3; ++i) {
    sum += foo((b + i) * s);
  }

into

  sum += foo(b * s);
  sum += foo((b + 1) * s);
  sum += foo((b + 2) * s);

However, no optimizations yet reduce the internal redundancy of the three
expressions:

  b * s
  (b + 1) * s
  (b + 2) * s

With SLSR, LLVM can optimize these three expressions into:

  t1 = b * s
  t2 = t1 + s
  t3 = t2 + s

This commit is only an initial step towards implementing a series of such
optimizations. I will implement more (see TODO in the file commentary) in the
near future. This optimization is enabled for the NVPTX backend for now.
However, I am more than happy to push it to the standard optimization pipeline
after more thorough performance tests.

Test Plan: test/StraightLineStrengthReduce/slsr.ll

Reviewers: eliben, HaoLiu, meheff, hfinkel, jholewinski, atrick

Reviewed By: jholewinski, atrick

Subscribers: karthikthecool, jholewinski, llvm-commits

Differential Revision: http://reviews.llvm.org/D7310

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228016 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-03 19:37:06 +00:00

229 lines
7.0 KiB
C++

//===-- Scalar.cpp --------------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements common infrastructure for libLLVMScalarOpts.a, which
// implements several scalar transformations over the LLVM intermediate
// representation, including the C bindings for that library.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar.h"
#include "llvm-c/Initialization.h"
#include "llvm-c/Transforms/Scalar.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Verifier.h"
#include "llvm/InitializePasses.h"
#include "llvm/PassManager.h"
using namespace llvm;
/// initializeScalarOptsPasses - Initialize all passes linked into the
/// ScalarOpts library.
void llvm::initializeScalarOpts(PassRegistry &Registry) {
initializeADCEPass(Registry);
initializeAlignmentFromAssumptionsPass(Registry);
initializeSampleProfileLoaderPass(Registry);
initializeConstantHoistingPass(Registry);
initializeConstantPropagationPass(Registry);
initializeCorrelatedValuePropagationPass(Registry);
initializeDCEPass(Registry);
initializeDeadInstEliminationPass(Registry);
initializeScalarizerPass(Registry);
initializeDSEPass(Registry);
initializeGVNPass(Registry);
initializeEarlyCSELegacyPassPass(Registry);
initializeFlattenCFGPassPass(Registry);
initializeInductiveRangeCheckEliminationPass(Registry);
initializeIndVarSimplifyPass(Registry);
initializeJumpThreadingPass(Registry);
initializeLICMPass(Registry);
initializeLoopDeletionPass(Registry);
initializeLoopInstSimplifyPass(Registry);
initializeLoopRotatePass(Registry);
initializeLoopStrengthReducePass(Registry);
initializeLoopRerollPass(Registry);
initializeLoopUnrollPass(Registry);
initializeLoopUnswitchPass(Registry);
initializeLoopIdiomRecognizePass(Registry);
initializeLowerAtomicPass(Registry);
initializeLowerExpectIntrinsicPass(Registry);
initializeMemCpyOptPass(Registry);
initializeMergedLoadStoreMotionPass(Registry);
initializePartiallyInlineLibCallsPass(Registry);
initializeReassociatePass(Registry);
initializeRegToMemPass(Registry);
initializeSCCPPass(Registry);
initializeIPSCCPPass(Registry);
initializeSROAPass(Registry);
initializeSROA_DTPass(Registry);
initializeSROA_SSAUpPass(Registry);
initializeCFGSimplifyPassPass(Registry);
initializeStructurizeCFGPass(Registry);
initializeSinkingPass(Registry);
initializeTailCallElimPass(Registry);
initializeSeparateConstOffsetFromGEPPass(Registry);
initializeStraightLineStrengthReducePass(Registry);
initializeLoadCombinePass(Registry);
}
void LLVMInitializeScalarOpts(LLVMPassRegistryRef R) {
initializeScalarOpts(*unwrap(R));
}
void LLVMAddAggressiveDCEPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createAggressiveDCEPass());
}
void LLVMAddAlignmentFromAssumptionsPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createAlignmentFromAssumptionsPass());
}
void LLVMAddCFGSimplificationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createCFGSimplificationPass());
}
void LLVMAddDeadStoreEliminationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createDeadStoreEliminationPass());
}
void LLVMAddScalarizerPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createScalarizerPass());
}
void LLVMAddGVNPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createGVNPass());
}
void LLVMAddMergedLoadStoreMotionPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createMergedLoadStoreMotionPass());
}
void LLVMAddIndVarSimplifyPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createIndVarSimplifyPass());
}
void LLVMAddInstructionCombiningPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createInstructionCombiningPass());
}
void LLVMAddJumpThreadingPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createJumpThreadingPass());
}
void LLVMAddLICMPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLICMPass());
}
void LLVMAddLoopDeletionPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopDeletionPass());
}
void LLVMAddLoopIdiomPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopIdiomPass());
}
void LLVMAddLoopRotatePass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopRotatePass());
}
void LLVMAddLoopRerollPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopRerollPass());
}
void LLVMAddLoopUnrollPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopUnrollPass());
}
void LLVMAddLoopUnswitchPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopUnswitchPass());
}
void LLVMAddMemCpyOptPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createMemCpyOptPass());
}
void LLVMAddPartiallyInlineLibCallsPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createPartiallyInlineLibCallsPass());
}
void LLVMAddLowerSwitchPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLowerSwitchPass());
}
void LLVMAddPromoteMemoryToRegisterPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createPromoteMemoryToRegisterPass());
}
void LLVMAddReassociatePass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createReassociatePass());
}
void LLVMAddSCCPPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createSCCPPass());
}
void LLVMAddScalarReplAggregatesPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createScalarReplAggregatesPass());
}
void LLVMAddScalarReplAggregatesPassSSA(LLVMPassManagerRef PM) {
unwrap(PM)->add(createScalarReplAggregatesPass(-1, false));
}
void LLVMAddScalarReplAggregatesPassWithThreshold(LLVMPassManagerRef PM,
int Threshold) {
unwrap(PM)->add(createScalarReplAggregatesPass(Threshold));
}
void LLVMAddSimplifyLibCallsPass(LLVMPassManagerRef PM) {
// NOTE: The simplify-libcalls pass has been removed.
}
void LLVMAddTailCallEliminationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createTailCallEliminationPass());
}
void LLVMAddConstantPropagationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createConstantPropagationPass());
}
void LLVMAddDemoteMemoryToRegisterPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createDemoteRegisterToMemoryPass());
}
void LLVMAddVerifierPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createVerifierPass());
// FIXME: should this also add createDebugInfoVerifierPass()?
}
void LLVMAddCorrelatedValuePropagationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createCorrelatedValuePropagationPass());
}
void LLVMAddEarlyCSEPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createEarlyCSEPass());
}
void LLVMAddTypeBasedAliasAnalysisPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createTypeBasedAliasAnalysisPass());
}
void LLVMAddScopedNoAliasAAPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createScopedNoAliasAAPass());
}
void LLVMAddBasicAliasAnalysisPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createBasicAliasAnalysisPass());
}
void LLVMAddLowerExpectIntrinsicPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLowerExpectIntrinsicPass());
}