[PATCH] D16382: Add LoopSimplifyCFG pass
Justin Bogner via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 29 13:13:57 PST 2016
escha via llvm-commits <llvm-commits at lists.llvm.org> writes:
> escha added a comment.
>
> ping?
The comments and LGTM I sent a week ago still apply... Copied here in
case you lost them somehow.
Justin Bogner <mail at justinbogner.com> writes:
> escha via llvm-commits <llvm-commits at lists.llvm.org> writes:
>> escha updated this revision to Diff 45565.
>> escha added a comment.
>>
>> Updated diff with suggested changes.
>
> This is great. A couple of minor comments below and then this LGTM.
>
>>
>> Repository:
>> rL LLVM
>>
>> http://reviews.llvm.org/D16382
>>
>> Files:
>> include/llvm/InitializePasses.h
>> include/llvm/LinkAllPasses.h
>> include/llvm/Transforms/Scalar.h
>> lib/Transforms/Scalar/CMakeLists.txt
>> lib/Transforms/Scalar/LoopSimplifyCFG.cpp
>> lib/Transforms/Scalar/Scalar.cpp
>> test/Transforms/LoopSimplifyCFG/merge-header.ll
>>
>>
>> Index: test/Transforms/LoopSimplifyCFG/merge-header.ll
>> ===================================================================
>> --- test/Transforms/LoopSimplifyCFG/merge-header.ll
>> +++ test/Transforms/LoopSimplifyCFG/merge-header.ll
>> @@ -0,0 +1,30 @@
>> +; RUN: opt -S -loop-simplifycfg < %s | FileCheck %s
>> +
>> +; CHECK-LABEL: foo
>> +; CHECK: entry
>> +; CHECK-NEXT: br label %inner
>> +define i32 @foo(i32* %P, i64* %Q) {
>> +entry:
>> + br label %outer
>> +
>> +outer: ; preds = %outer.latch2, %entry
>> + %y.2 = phi i32 [ 0, %entry ], [ %y.inc2, %outer.latch2 ]
>> + br label %inner
>> +
>> +inner: ; preds = %outer
>> + store i32 0, i32* %P
>> + store i32 1, i32* %P
>> + store i32 2, i32* %P
>> + %y.inc2 = add nsw i32 %y.2, 1
>> + %exitcond.outer = icmp eq i32 %y.inc2, 3
>> + store i32 %y.2, i32* %P
>> + br i1 %exitcond.outer, label %exit, label %outer.latch2
>> +
>> +outer.latch2: ; preds = %inner
>> + %t = sext i32 %y.inc2 to i64
>> + store i64 %t, i64* %Q
>> + br label %outer
>> +
>> +exit: ; preds = %inner
>> + ret i32 0
>> +}
>> Index: lib/Transforms/Scalar/Scalar.cpp
>> ===================================================================
>> --- lib/Transforms/Scalar/Scalar.cpp
>> +++ lib/Transforms/Scalar/Scalar.cpp
>> @@ -84,6 +84,7 @@
>> initializeFloat2IntPass(Registry);
>> initializeLoopDistributePass(Registry);
>> initializeLoopLoadEliminationPass(Registry);
>> + initializeLoopSimplifyCFGPass(Registry);
>> }
>>
>> void LLVMInitializeScalarOpts(LLVMPassRegistryRef R) {
>> @@ -154,6 +155,10 @@
>> unwrap(PM)->add(createLoopRerollPass());
>> }
>>
>> +void LLVMAddLoopSimplifyCFGPass(LLVMPassManagerRef PM) {
>> + unwrap(PM)->add(createLoopSimplifyCFGPass());
>> +}
>> +
>> void LLVMAddLoopUnrollPass(LLVMPassManagerRef PM) {
>> unwrap(PM)->add(createLoopUnrollPass());
>> }
>> Index: lib/Transforms/Scalar/LoopSimplifyCFG.cpp
>> ===================================================================
>> --- lib/Transforms/Scalar/LoopSimplifyCFG.cpp
>> +++ lib/Transforms/Scalar/LoopSimplifyCFG.cpp
>> @@ -0,0 +1,114 @@
>> +//===--------- LoopSimplifyCFG.cpp - Loop CFG Simplification Pass ---------===//
>> +//
>> +// The LLVM Compiler Infrastructure
>> +//
>> +// This file is distributed under the University of Illinois Open Source
>> +// License. See LICENSE.TXT for details.
>> +//
>> +//===----------------------------------------------------------------------===//
>> +//
>> +// This file implements the Loop SimplifyCFG Pass. This pass is responsible for
>> +// basic loop CFG cleanup, primarily to assist other loop passes. If you
>> +// encounter a noncanonical CFG construct that causes another loop pass to
>> +// perform suboptimally, this is the place to fix it up.
>> +//
>> +//===----------------------------------------------------------------------===//
>> +
>> +#include "llvm/Transforms/Scalar.h"
>> +#include "llvm/ADT/SmallVector.h"
>> +#include "llvm/ADT/Statistic.h"
>> +#include "llvm/Analysis/AliasAnalysis.h"
>> +#include "llvm/Analysis/BasicAliasAnalysis.h"
>> +#include "llvm/Analysis/AssumptionCache.h"
>> +#include "llvm/Analysis/DependenceAnalysis.h"
>> +#include "llvm/Analysis/GlobalsModRef.h"
>> +#include "llvm/Analysis/LoopInfo.h"
>> +#include "llvm/Analysis/LoopPass.h"
>> +#include "llvm/Analysis/ScalarEvolution.h"
>> +#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
>> +#include "llvm/Analysis/TargetTransformInfo.h"
>> +#include "llvm/IR/Dominators.h"
>> +#include "llvm/Transforms/Utils/Local.h"
>> +using namespace llvm;
>> +
>> +#define DEBUG_TYPE "loop-simplifycfg"
>> +
>> +namespace {
>> +class LoopSimplifyCFG : public LoopPass {
>> +public:
>> + static char ID; // Pass ID, replacement for typeid
>> + LoopSimplifyCFG() : LoopPass(ID) {
>> + initializeLoopSimplifyCFGPass(*PassRegistry::getPassRegistry());
>> + }
>> +
>> + bool runOnLoop(Loop *L, LPPassManager &) override;
>> +
>> + void getAnalysisUsage(AnalysisUsage &AU) const override {
>> + AU.addRequired<DominatorTreeWrapperPass>();
>> + AU.addRequired<LoopInfoWrapperPass>();
>> +
>> + AU.addPreserved<DominatorTreeWrapperPass>();
>> + AU.addPreserved<LoopInfoWrapperPass>();
>> + AU.addPreserved<GlobalsAAWrapperPass>();
>> + AU.addPreserved<BasicAAWrapperPass>();
>> + AU.addPreserved<AAResultsWrapperPass>();
>> + AU.addPreserved<ScalarEvolutionWrapperPass>();
>> + AU.addPreserved<SCEVAAWrapperPass>();
>> + AU.addPreserved<DependenceAnalysis>();
>> + AU.addPreservedID(LoopSimplifyID);
>> + AU.addPreservedID(LCSSAID);
>> + }
>> +};
>> +}
>> +
>> +char LoopSimplifyCFG::ID = 0;
>> +INITIALIZE_PASS_BEGIN(LoopSimplifyCFG, "loop-simplifycfg", "Simplify loop CFG",
>> + false, false)
>> +INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
>> +INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
>> +INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)
>> +INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
>> +INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
>> +INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
>> +INITIALIZE_PASS_DEPENDENCY(LCSSA)
>> +INITIALIZE_PASS_DEPENDENCY(SCEVAAWrapperPass)
>> +INITIALIZE_PASS_DEPENDENCY(BasicAAWrapperPass)
>> +INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)
>> +INITIALIZE_PASS_END(LoopSimplifyCFG, "loop-simplifycfg", "Simplify loop CFG",
>> + false, false)
>> +
>> +Pass *llvm::createLoopSimplifyCFGPass() { return new LoopSimplifyCFG(); }
>> +
>> +/// runOnLoop - Perform basic CFG simplifications to assist other loop passes.
>> +/// For now, this only attempts to merge blocks in the trivial case.
>> +bool LoopSimplifyCFG::runOnLoop(Loop *L, LPPassManager &) {
>
> You don't necessarily have to, but it'd make porting this to the new PM
> later very trivial if you formulate the work here as a static function
> and have runOnLoop just grab the analyses and call that. Ie, implement:
>
> static bool simplifyLoopCFG(Loop *L, DominatorTree *DT, LoopInfo *LI) { ... }
>
> and then...
>
>> + if (skipOptnoneFunction(L))
>> + return false;
>> +
>> + bool changed = false;
>> + DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
>> + LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
>
> runOnLoop is just this top part and a call to the static function.
>
>> +
>> + // Copy blocks into a temporary array to avoid iterator invalidation issues
>> + // as we remove them.
>> + SmallVector<BasicBlock *, 16> Blocks;
>> + Blocks.append(L->block_begin(), L->block_end());
>
> I think you can shorten this to just:
>
> SmallVector<BasicBlock *, 16> Blocks(L->blocks());
>
>> +
>> + for (auto Block : Blocks) {
>
> Please use "auto *" so it's obvious this doesn't do any copies.
>
>> + // Attempt to merge blocks in the trivial case. Don't modify blocks which
>> + // belong to other loops.
>> + BasicBlock *Succ = Block;
>> + BasicBlock *Pred = Succ->getSinglePredecessor();
>> + if (!Pred || !Pred->getSingleSuccessor() || LI->getLoopFor(Pred) != L)
>> + continue;
>> +
>> + // Pred is going to disappear, so we need to update the loop info.
>> + if (L->getHeader() == Pred)
>> + L->moveToHeader(Succ);
>> + LI->removeBlock(Pred);
>> + MergeBasicBlockIntoOnlyPred(Succ, DT);
>> + changed = true;
>> + }
>> +
>> + return changed;
>> +}
>> Index: lib/Transforms/Scalar/CMakeLists.txt
>> ===================================================================
>> --- lib/Transforms/Scalar/CMakeLists.txt
>> +++ lib/Transforms/Scalar/CMakeLists.txt
>> @@ -24,6 +24,7 @@
>> LoopLoadElimination.cpp
>> LoopRerollPass.cpp
>> LoopRotation.cpp
>> + LoopSimplifyCFG.cpp
>> LoopStrengthReduce.cpp
>> LoopUnrollPass.cpp
>> LoopUnswitch.cpp
>> Index: include/llvm/Transforms/Scalar.h
>> ===================================================================
>> --- include/llvm/Transforms/Scalar.h
>> +++ include/llvm/Transforms/Scalar.h
>> @@ -493,6 +493,13 @@
>> //
>> FunctionPass *createLoopLoadEliminationPass();
>>
>> +//===----------------------------------------------------------------------===//
>> +//
>> +// LoopSimplifyCFG - This pass performs basic CFG simplification on loops,
>> +// primarily to help other loop passes.
>> +//
>> +Pass *createLoopSimplifyCFGPass();
>> +
>> } // End llvm namespace
>>
>> #endif
>> Index: include/llvm/LinkAllPasses.h
>> ===================================================================
>> --- include/llvm/LinkAllPasses.h
>> +++ include/llvm/LinkAllPasses.h
>> @@ -106,6 +106,7 @@
>> (void) llvm::createLoopExtractorPass();
>> (void) llvm::createLoopInterchangePass();
>> (void) llvm::createLoopSimplifyPass();
>> + (void) llvm::createLoopSimplifyCFGPass();
>> (void) llvm::createLoopStrengthReducePass();
>> (void) llvm::createLoopRerollPass();
>> (void) llvm::createLoopUnrollPass();
>> Index: include/llvm/InitializePasses.h
>> ===================================================================
>> --- include/llvm/InitializePasses.h
>> +++ include/llvm/InitializePasses.h
>> @@ -170,6 +170,7 @@
>> void initializeLoopInstSimplifyPass(PassRegistry&);
>> void initializeLoopRotatePass(PassRegistry&);
>> void initializeLoopSimplifyPass(PassRegistry&);
>> +void initializeLoopSimplifyCFGPass(PassRegistry&);
>> void initializeLoopStrengthReducePass(PassRegistry&);
>> void initializeGlobalMergePass(PassRegistry&);
>> void initializeLoopRerollPass(PassRegistry&);
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
More information about the llvm-commits
mailing list