[llvm] r259256 - Add LoopSimplifyCFG pass
Sanjoy Das via llvm-commits
llvm-commits at lists.llvm.org
Fri Jan 29 15:00:26 PST 2016
Fiona Glaser via llvm-commits wrote:
> Author: escha
> Date: Fri Jan 29 16:35:36 2016
> New Revision: 259256
>
> URL: http://llvm.org/viewvc/llvm-project?rev=259256&view=rev
> Log:
> Add LoopSimplifyCFG pass
>
> Loop transformations can sometimes fail because the loop, while in
> valid rotated LCSSA form, is not in a canonical CFG form. This is
> an extremely simple pass that just merges obviously redundant
> blocks, which can be used to fix some known failure cases. In the
> future, it may be enhanced with more cases (and have code shared with
> SimplifyCFG).
>
> This allows us to run LoopSimplifyCFG -> LoopRotate -> LoopUnroll,
> so that SimplifyCFG cleans up the loop before Rotate tries to run.
>
> Not currently used in the pass manager, since this pass doesn't do
> anything unless you can hook it up in an LPM with other loop passes.
> It'll be added once Chandler cleans up things to allow this.
>
> Tested in a custom pipeline out of tree to confirm it works in
> practice (in addition to the included trivial test).
>
> Added:
> llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
> llvm/trunk/test/Transforms/LoopSimplifyCFG/
> llvm/trunk/test/Transforms/LoopSimplifyCFG/merge-header.ll
> Modified:
> llvm/trunk/include/llvm/InitializePasses.h
> llvm/trunk/include/llvm/LinkAllPasses.h
> llvm/trunk/include/llvm/Transforms/Scalar.h
> llvm/trunk/lib/Transforms/Scalar/CMakeLists.txt
> llvm/trunk/lib/Transforms/Scalar/Scalar.cpp
>
> Modified: llvm/trunk/include/llvm/InitializePasses.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/InitializePasses.h?rev=259256&r1=259255&r2=259256&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/InitializePasses.h (original)
> +++ llvm/trunk/include/llvm/InitializePasses.h Fri Jan 29 16:35:36 2016
> @@ -170,6 +170,7 @@ void initializeLoopInterchangePass(PassR
> void initializeLoopInstSimplifyPass(PassRegistry&);
> void initializeLoopRotatePass(PassRegistry&);
> void initializeLoopSimplifyPass(PassRegistry&);
> +void initializeLoopSimplifyCFGPass(PassRegistry&);
> void initializeLoopStrengthReducePass(PassRegistry&);
> void initializeGlobalMergePass(PassRegistry&);
> void initializeLoopRerollPass(PassRegistry&);
>
> Modified: llvm/trunk/include/llvm/LinkAllPasses.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/LinkAllPasses.h?rev=259256&r1=259255&r2=259256&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/LinkAllPasses.h (original)
> +++ llvm/trunk/include/llvm/LinkAllPasses.h Fri Jan 29 16:35:36 2016
> @@ -106,6 +106,7 @@ namespace {
> (void) llvm::createLoopExtractorPass();
> (void) llvm::createLoopInterchangePass();
> (void) llvm::createLoopSimplifyPass();
> + (void) llvm::createLoopSimplifyCFGPass();
> (void) llvm::createLoopStrengthReducePass();
> (void) llvm::createLoopRerollPass();
> (void) llvm::createLoopUnrollPass();
>
> Modified: llvm/trunk/include/llvm/Transforms/Scalar.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Scalar.h?rev=259256&r1=259255&r2=259256&view=diff
> ==============================================================================
> --- llvm/trunk/include/llvm/Transforms/Scalar.h (original)
> +++ llvm/trunk/include/llvm/Transforms/Scalar.h Fri Jan 29 16:35:36 2016
> @@ -476,6 +476,13 @@ FunctionPass *createLoopDistributePass()
> //
> FunctionPass *createLoopLoadEliminationPass();
>
> +//===----------------------------------------------------------------------===//
> +//
> +// LoopSimplifyCFG - This pass performs basic CFG simplification on loops,
> +// primarily to help other loop passes.
> +//
> +Pass *createLoopSimplifyCFGPass();
> +
> } // End llvm namespace
>
> #endif
>
> Modified: llvm/trunk/lib/Transforms/Scalar/CMakeLists.txt
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CMakeLists.txt?rev=259256&r1=259255&r2=259256&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/CMakeLists.txt (original)
> +++ llvm/trunk/lib/Transforms/Scalar/CMakeLists.txt Fri Jan 29 16:35:36 2016
> @@ -24,6 +24,7 @@ add_llvm_library(LLVMScalarOpts
> LoopLoadElimination.cpp
> LoopRerollPass.cpp
> LoopRotation.cpp
> + LoopSimplifyCFG.cpp
> LoopStrengthReduce.cpp
> LoopUnrollPass.cpp
> LoopUnswitch.cpp
>
> Added: llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp?rev=259256&view=auto
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp (added)
> +++ llvm/trunk/lib/Transforms/Scalar/LoopSimplifyCFG.cpp Fri Jan 29 16:35:36 2016
> @@ -0,0 +1,111 @@
> +//===--------- 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_END(LoopSimplifyCFG, "loop-simplifycfg", "Simplify loop CFG",
> + false, false)
> +
> +Pass *llvm::createLoopSimplifyCFGPass() { return new LoopSimplifyCFG(); }
> +
> +static bool simplifyLoopCFG(Loop *L, DominatorTree *DT, LoopInfo *LI) {
> + bool Changed = false;
> + // Copy blocks into a temporary array to avoid iterator invalidation issues
> + // as we remove them.
> + SmallVector<WeakVH, 16> Blocks(L->blocks());
> +
> + for (auto&Block : Blocks) {
> + // Attempt to merge blocks in the trivial case. Don't modify blocks which
> + // belong to other loops.
> + BasicBlock *Succ = cast<BasicBlock>(Block);
cast<> does not allow a null argument, I think you want cast_or_null<> here.
> + if (!Succ)
> + continue;
> +
> + 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;
> +}
> +
> +/// 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&) {
> + if (skipOptnoneFunction(L))
> + return false;
> +
> + DominatorTree *DT =&getAnalysis<DominatorTreeWrapperPass>().getDomTree();
> + LoopInfo *LI =&getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
> + return simplifyLoopCFG(L, DT, LI);
> +}
>
> Modified: llvm/trunk/lib/Transforms/Scalar/Scalar.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/Scalar.cpp?rev=259256&r1=259255&r2=259256&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/Scalar.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/Scalar.cpp Fri Jan 29 16:35:36 2016
> @@ -84,6 +84,7 @@ void llvm::initializeScalarOpts(PassRegi
> initializeFloat2IntPass(Registry);
> initializeLoopDistributePass(Registry);
> initializeLoopLoadEliminationPass(Registry);
> + initializeLoopSimplifyCFGPass(Registry);
> }
>
> void LLVMInitializeScalarOpts(LLVMPassRegistryRef R) {
> @@ -154,6 +155,10 @@ void LLVMAddLoopRerollPass(LLVMPassManag
> unwrap(PM)->add(createLoopRerollPass());
> }
>
> +void LLVMAddLoopSimplifyCFGPass(LLVMPassManagerRef PM) {
> + unwrap(PM)->add(createLoopSimplifyCFGPass());
> +}
> +
> void LLVMAddLoopUnrollPass(LLVMPassManagerRef PM) {
> unwrap(PM)->add(createLoopUnrollPass());
> }
>
> Added: llvm/trunk/test/Transforms/LoopSimplifyCFG/merge-header.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/LoopSimplifyCFG/merge-header.ll?rev=259256&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/LoopSimplifyCFG/merge-header.ll (added)
> +++ llvm/trunk/test/Transforms/LoopSimplifyCFG/merge-header.ll Fri Jan 29 16:35:36 2016
> @@ -0,0 +1,34 @@
> +; RUN: opt -S -loop-simplifycfg< %s | FileCheck %s
> +
> +; CHECK-LABEL: foo
> +; CHECK: entry:
> +; CHECK-NEXT: br label %[[LOOP:[a-z]+]]
> +; CHECK: [[LOOP]]:
> +; CHECK-NEXT: phi
> +; CHECK-NOT: br label
> +; CHECK: br i1
> +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
> +}
>
>
> _______________________________________________
> 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