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llvm-mirror/lib/Transforms/Scalar/Scalar.cpp
Alexey Zhikhartsev 6516543c4b Add jump-threading optimization for deterministic finite automata
The current JumpThreading pass does not jump thread loops since it can
result in irreducible control flow that harms other optimizations. This
prevents switch statements inside a loop from being optimized to use
unconditional branches.

This code pattern occurs in the core_state_transition function of
Coremark. The state machine can be implemented manually with goto
statements resulting in a large runtime improvement, and this transform
makes the switch implementation match the goto version in performance.

This patch specifically targets switch statements inside a loop that
have the opportunity to be threaded. Once it identifies an opportunity,
it creates new paths that branch directly to the correct code block.
For example, the left CFG could be transformed to the right CFG:

```
          sw.bb                        sw.bb
        /   |   \                    /   |   \
   case1  case2  case3          case1  case2  case3
        \   |   /                /       |       \
        latch.bb             latch.2  latch.3  latch.1
         br sw.bb              /         |         \
                           sw.bb.2     sw.bb.3     sw.bb.1
                            br case2    br case3    br case1
```

Co-author: Justin Kreiner @jkreiner
Co-author: Ehsan Amiri @amehsan

Reviewed By: SjoerdMeijer

Differential Revision: https://reviews.llvm.org/D99205
2021-07-27 14:34:04 -04:00

309 lines
10 KiB
C++

//===-- Scalar.cpp --------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// 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/BasicAliasAnalysis.h"
#include "llvm/Analysis/Passes.h"
#include "llvm/Analysis/ScopedNoAliasAA.h"
#include "llvm/Analysis/TypeBasedAliasAnalysis.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Verifier.h"
#include "llvm/InitializePasses.h"
#include "llvm/Transforms/Scalar/GVN.h"
#include "llvm/Transforms/Scalar/Scalarizer.h"
#include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h"
#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
using namespace llvm;
/// initializeScalarOptsPasses - Initialize all passes linked into the
/// ScalarOpts library.
void llvm::initializeScalarOpts(PassRegistry &Registry) {
initializeADCELegacyPassPass(Registry);
initializeAnnotationRemarksLegacyPass(Registry);
initializeBDCELegacyPassPass(Registry);
initializeAlignmentFromAssumptionsPass(Registry);
initializeCallSiteSplittingLegacyPassPass(Registry);
initializeConstantHoistingLegacyPassPass(Registry);
initializeConstraintEliminationPass(Registry);
initializeCorrelatedValuePropagationPass(Registry);
initializeDCELegacyPassPass(Registry);
initializeDivRemPairsLegacyPassPass(Registry);
initializeScalarizerLegacyPassPass(Registry);
initializeDSELegacyPassPass(Registry);
initializeGuardWideningLegacyPassPass(Registry);
initializeLoopGuardWideningLegacyPassPass(Registry);
initializeGVNLegacyPassPass(Registry);
initializeNewGVNLegacyPassPass(Registry);
initializeEarlyCSELegacyPassPass(Registry);
initializeEarlyCSEMemSSALegacyPassPass(Registry);
initializeMakeGuardsExplicitLegacyPassPass(Registry);
initializeGVNHoistLegacyPassPass(Registry);
initializeGVNSinkLegacyPassPass(Registry);
initializeFlattenCFGPassPass(Registry);
initializeIRCELegacyPassPass(Registry);
initializeIndVarSimplifyLegacyPassPass(Registry);
initializeInferAddressSpacesPass(Registry);
initializeInstSimplifyLegacyPassPass(Registry);
initializeJumpThreadingPass(Registry);
initializeDFAJumpThreadingLegacyPassPass(Registry);
initializeLegacyLICMPassPass(Registry);
initializeLegacyLoopSinkPassPass(Registry);
initializeLoopFuseLegacyPass(Registry);
initializeLoopDataPrefetchLegacyPassPass(Registry);
initializeLoopDeletionLegacyPassPass(Registry);
initializeLoopAccessLegacyAnalysisPass(Registry);
initializeLoopInstSimplifyLegacyPassPass(Registry);
initializeLoopInterchangeLegacyPassPass(Registry);
initializeLoopFlattenLegacyPassPass(Registry);
initializeLoopPredicationLegacyPassPass(Registry);
initializeLoopRotateLegacyPassPass(Registry);
initializeLoopStrengthReducePass(Registry);
initializeLoopRerollLegacyPassPass(Registry);
initializeLoopUnrollPass(Registry);
initializeLoopUnrollAndJamPass(Registry);
initializeLoopUnswitchPass(Registry);
initializeWarnMissedTransformationsLegacyPass(Registry);
initializeLoopVersioningLICMLegacyPassPass(Registry);
initializeLoopIdiomRecognizeLegacyPassPass(Registry);
initializeLowerAtomicLegacyPassPass(Registry);
initializeLowerConstantIntrinsicsPass(Registry);
initializeLowerExpectIntrinsicPass(Registry);
initializeLowerGuardIntrinsicLegacyPassPass(Registry);
initializeLowerMatrixIntrinsicsLegacyPassPass(Registry);
initializeLowerMatrixIntrinsicsMinimalLegacyPassPass(Registry);
initializeLowerWidenableConditionLegacyPassPass(Registry);
initializeMemCpyOptLegacyPassPass(Registry);
initializeMergeICmpsLegacyPassPass(Registry);
initializeMergedLoadStoreMotionLegacyPassPass(Registry);
initializeNaryReassociateLegacyPassPass(Registry);
initializePartiallyInlineLibCallsLegacyPassPass(Registry);
initializeReassociateLegacyPassPass(Registry);
initializeRedundantDbgInstEliminationPass(Registry);
initializeRegToMemLegacyPass(Registry);
initializeRewriteStatepointsForGCLegacyPassPass(Registry);
initializeScalarizeMaskedMemIntrinLegacyPassPass(Registry);
initializeSCCPLegacyPassPass(Registry);
initializeSROALegacyPassPass(Registry);
initializeCFGSimplifyPassPass(Registry);
initializeStructurizeCFGLegacyPassPass(Registry);
initializeSimpleLoopUnswitchLegacyPassPass(Registry);
initializeSinkingLegacyPassPass(Registry);
initializeTailCallElimPass(Registry);
initializeSeparateConstOffsetFromGEPLegacyPassPass(Registry);
initializeSpeculativeExecutionLegacyPassPass(Registry);
initializeStraightLineStrengthReduceLegacyPassPass(Registry);
initializePlaceBackedgeSafepointsImplPass(Registry);
initializePlaceSafepointsPass(Registry);
initializeFloat2IntLegacyPassPass(Registry);
initializeLoopDistributeLegacyPass(Registry);
initializeLoopLoadEliminationPass(Registry);
initializeLoopSimplifyCFGLegacyPassPass(Registry);
initializeLoopVersioningLegacyPassPass(Registry);
initializeEntryExitInstrumenterPass(Registry);
initializePostInlineEntryExitInstrumenterPass(Registry);
}
void LLVMAddLoopSimplifyCFGPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopSimplifyCFGPass());
}
void LLVMInitializeScalarOpts(LLVMPassRegistryRef R) {
initializeScalarOpts(*unwrap(R));
}
void LLVMAddAggressiveDCEPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createAggressiveDCEPass());
}
void LLVMAddDCEPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createDeadCodeEliminationPass());
}
void LLVMAddBitTrackingDCEPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createBitTrackingDCEPass());
}
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 LLVMAddNewGVNPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createNewGVNPass());
}
void LLVMAddMergedLoadStoreMotionPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createMergedLoadStoreMotionPass());
}
void LLVMAddIndVarSimplifyPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createIndVarSimplifyPass());
}
void LLVMAddInstructionSimplifyPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createInstSimplifyLegacyPass());
}
void LLVMAddJumpThreadingPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createJumpThreadingPass());
}
void LLVMAddLoopSinkPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopSinkPass());
}
void LLVMAddLICMPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLICMPass());
}
void LLVMAddLoopDeletionPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopDeletionPass());
}
void LLVMAddLoopFlattenPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopFlattenPass());
}
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 LLVMAddLoopUnrollAndJamPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopUnrollAndJamPass());
}
void LLVMAddLoopUnswitchPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLoopUnswitchPass());
}
void LLVMAddLowerAtomicPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLowerAtomicPass());
}
void LLVMAddMemCpyOptPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createMemCpyOptPass());
}
void LLVMAddPartiallyInlineLibCallsPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createPartiallyInlineLibCallsPass());
}
void LLVMAddReassociatePass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createReassociatePass());
}
void LLVMAddSCCPPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createSCCPPass());
}
void LLVMAddScalarReplAggregatesPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createSROAPass());
}
void LLVMAddScalarReplAggregatesPassSSA(LLVMPassManagerRef PM) {
unwrap(PM)->add(createSROAPass());
}
void LLVMAddScalarReplAggregatesPassWithThreshold(LLVMPassManagerRef PM,
int Threshold) {
unwrap(PM)->add(createSROAPass());
}
void LLVMAddSimplifyLibCallsPass(LLVMPassManagerRef PM) {
// NOTE: The simplify-libcalls pass has been removed.
}
void LLVMAddTailCallEliminationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createTailCallEliminationPass());
}
void LLVMAddDemoteMemoryToRegisterPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createDemoteRegisterToMemoryPass());
}
void LLVMAddVerifierPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createVerifierPass());
}
void LLVMAddCorrelatedValuePropagationPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createCorrelatedValuePropagationPass());
}
void LLVMAddEarlyCSEPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createEarlyCSEPass(false/*=UseMemorySSA*/));
}
void LLVMAddEarlyCSEMemSSAPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createEarlyCSEPass(true/*=UseMemorySSA*/));
}
void LLVMAddGVNHoistLegacyPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createGVNHoistPass());
}
void LLVMAddTypeBasedAliasAnalysisPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createTypeBasedAAWrapperPass());
}
void LLVMAddScopedNoAliasAAPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createScopedNoAliasAAWrapperPass());
}
void LLVMAddBasicAliasAnalysisPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createBasicAAWrapperPass());
}
void LLVMAddLowerConstantIntrinsicsPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLowerConstantIntrinsicsPass());
}
void LLVMAddLowerExpectIntrinsicPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createLowerExpectIntrinsicPass());
}
void LLVMAddUnifyFunctionExitNodesPass(LLVMPassManagerRef PM) {
unwrap(PM)->add(createUnifyFunctionExitNodesPass());
}