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Remove the LoopInstSimplify pass (-loop-instsimplify)

Browse Source 
LoopInstSimplify is unused and untested. Reading through the commit
history the pass also seems to have a high maintenance burden.

It would be best to retire the pass for now. It should be easy to
recover if we need something similar in the future.

Differential Revision: https://reviews.llvm.org/D44053

llvm-svn: 327329
This commit is contained in:
Vedant Kumar 2018-03-12 20:49:42 +00:00
parent 074a79622f
commit 637b806500
10 changed files with 5 additions and 273 deletions
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2
docs/ReleaseNotes.rst
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@ -40,6 +40,8 @@ Non-comprehensive list of changes in this release
functionality, or simply have a lot to talk about), see the `NOTE` below
for adding a new subsection.
* The LoopInstSimplify pass (-loop-instsimplify) has been removed.
* Note..
.. NOTE

1
include/llvm/InitializePasses.h
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@ -210,7 +210,6 @@ void initializeLoopDistributeLegacyPass(PassRegistry&);
void initializeLoopExtractorPass(PassRegistry&);
void initializeLoopIdiomRecognizeLegacyPassPass(PassRegistry&);
void initializeLoopInfoWrapperPassPass(PassRegistry&);
void initializeLoopInstSimplifyLegacyPassPass(PassRegistry&);
void initializeLoopInterchangePass(PassRegistry&);
void initializeLoopLoadEliminationPass(PassRegistry&);
void initializeLoopPassPass(PassRegistry&);

6
include/llvm/Transforms/Scalar.h
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@ -187,12 +187,6 @@ Pass *createLoopStrengthReducePass();
Pass *createLoopUnswitchPass(bool OptimizeForSize = false,
bool hasBranchDivergence = false);
//===----------------------------------------------------------------------===//
//
// LoopInstSimplify - This pass simplifies instructions in a loop's body.
//
Pass *createLoopInstSimplifyPass();
//===----------------------------------------------------------------------===//
//
// LoopUnroll - This pass is a simple loop unrolling pass.

34
include/llvm/Transforms/Scalar/LoopInstSimplify.h
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@ -1,34 +0,0 @@
//===- LoopInstSimplify.h - Loop Inst Simplify Pass -------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass performs lightweight instruction simplification on loop bodies.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_TRANSFORMS_SCALAR_LOOPINSTSIMPLIFY_H
#define LLVM_TRANSFORMS_SCALAR_LOOPINSTSIMPLIFY_H
#include "llvm/Analysis/LoopAnalysisManager.h"
#include "llvm/IR/PassManager.h"
namespace llvm {
class Loop;
class LPMUpdater;
/// Performs Loop Inst Simplify Pass.
class LoopInstSimplifyPass : public PassInfoMixin<LoopInstSimplifyPass> {
public:
PreservedAnalyses run(Loop &L, LoopAnalysisManager &AM,
LoopStandardAnalysisResults &AR, LPMUpdater &U);
};
} // end namespace llvm
#endif // LLVM_TRANSFORMS_SCALAR_LOOPINSTSIMPLIFY_H

6
lib/Passes/PassBuilder.cpp
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@ -110,7 +110,6 @@
#include "llvm/Transforms/Scalar/LoopDeletion.h"
#include "llvm/Transforms/Scalar/LoopDistribute.h"
#include "llvm/Transforms/Scalar/LoopIdiomRecognize.h"
#include "llvm/Transforms/Scalar/LoopInstSimplify.h"
#include "llvm/Transforms/Scalar/LoopLoadElimination.h"
#include "llvm/Transforms/Scalar/LoopPassManager.h"
#include "llvm/Transforms/Scalar/LoopPredication.h"
@ -391,9 +390,8 @@ PassBuilder::buildFunctionSimplificationPipeline(OptimizationLevel Level,
// FIXME: Currently this is split into two loop pass pipelines because we run
// some function passes in between them. These can and should be replaced by
// loop pass equivalenst but those aren't ready yet. Specifically,
// `SimplifyCFGPass` and `InstCombinePass` are used. We have
// `LoopSimplifyCFGPass` which isn't yet powerful enough, and the closest to
// the other we have is `LoopInstSimplify`.
// `SimplifyCFGPass` and `InstCombinePass` are used. We just have
// `LoopSimplifyCFGPass` which isn't yet powerful enough.
LoopPassManager LPM1(DebugLogging), LPM2(DebugLogging);
// Rotate Loop - disable header duplication at -Oz

1
lib/Passes/PassRegistry.def
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@ -230,7 +230,6 @@ LOOP_ANALYSIS("ivusers", IVUsersAnalysis())
LOOP_PASS("invalidate<all>", InvalidateAllAnalysesPass())
LOOP_PASS("licm", LICMPass())
LOOP_PASS("loop-idiom", LoopIdiomRecognizePass())
LOOP_PASS("loop-instsimplify", LoopInstSimplifyPass())
LOOP_PASS("rotate", LoopRotatePass())
LOOP_PASS("no-op-loop", NoOpLoopPass())
LOOP_PASS("print", PrintLoopPass(dbgs()))

1
lib/Transforms/Scalar/CMakeLists.txt
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@ -28,7 +28,6 @@ add_llvm_library(LLVMScalarOpts
LoopDataPrefetch.cpp
LoopDistribute.cpp
LoopIdiomRecognize.cpp
LoopInstSimplify.cpp
LoopInterchange.cpp
LoopLoadElimination.cpp
LoopPassManager.cpp

223
lib/Transforms/Scalar/LoopInstSimplify.cpp
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@ -1,223 +0,0 @@
//===- LoopInstSimplify.cpp - Loop Instruction Simplification Pass --------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass performs lightweight instruction simplification on loop bodies.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar/LoopInstSimplify.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/LoopPass.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/PassManager.h"
#include "llvm/IR/User.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Utils/LoopUtils.h"
#include <algorithm>
#include <utility>
using namespace llvm;
#define DEBUG_TYPE "loop-instsimplify"
STATISTIC(NumSimplified, "Number of redundant instructions simplified");
static bool SimplifyLoopInst(Loop *L, DominatorTree *DT, LoopInfo *LI,
AssumptionCache *AC,
const TargetLibraryInfo *TLI) {
SmallVector<BasicBlock *, 8> ExitBlocks;
L->getUniqueExitBlocks(ExitBlocks);
array_pod_sort(ExitBlocks.begin(), ExitBlocks.end());
SmallPtrSet<const Instruction *, 8> S1, S2, *ToSimplify = &S1, *Next = &S2;
// The bit we are stealing from the pointer represents whether this basic
// block is the header of a subloop, in which case we only process its phis.
using WorklistItem = PointerIntPair<BasicBlock *, 1>;
SmallVector<WorklistItem, 16> VisitStack;
SmallPtrSet<BasicBlock *, 32> Visited;
bool Changed = false;
bool LocalChanged;
do {
LocalChanged = false;
VisitStack.clear();
Visited.clear();
VisitStack.push_back(WorklistItem(L->getHeader(), false));
while (!VisitStack.empty()) {
WorklistItem Item = VisitStack.pop_back_val();
BasicBlock *BB = Item.getPointer();
bool IsSubloopHeader = Item.getInt();
const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
// Simplify instructions in the current basic block.
for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
Instruction *I = &*BI++;
// The first time through the loop ToSimplify is empty and we try to
// simplify all instructions. On later iterations ToSimplify is not
// empty and we only bother simplifying instructions that are in it.
if (!ToSimplify->empty() && !ToSimplify->count(I))
continue;
// Don't bother simplifying unused instructions.
if (!I->use_empty()) {
Value *V = SimplifyInstruction(I, {DL, TLI, DT, AC});
if (V && LI->replacementPreservesLCSSAForm(I, V)) {
// Mark all uses for resimplification next time round the loop.
for (User *U : I->users())
Next->insert(cast<Instruction>(U));
I->replaceAllUsesWith(V);
LocalChanged = true;
++NumSimplified;
}
}
if (RecursivelyDeleteTriviallyDeadInstructions(I, TLI)) {
// RecursivelyDeleteTriviallyDeadInstruction can remove more than one
// instruction, so simply incrementing the iterator does not work.
// When instructions get deleted re-iterate instead.
BI = BB->begin();
BE = BB->end();
LocalChanged = true;
}
if (IsSubloopHeader && !isa<PHINode>(I))
break;
}
// Add all successors to the worklist, except for loop exit blocks and the
// bodies of subloops. We visit the headers of loops so that we can
// process
// their phis, but we contract the rest of the subloop body and only
// follow
// edges leading back to the original loop.
for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE;
++SI) {
BasicBlock *SuccBB = *SI;
if (!Visited.insert(SuccBB).second)
continue;
const Loop *SuccLoop = LI->getLoopFor(SuccBB);
if (SuccLoop && SuccLoop->getHeader() == SuccBB &&
L->contains(SuccLoop)) {
VisitStack.push_back(WorklistItem(SuccBB, true));
SmallVector<BasicBlock *, 8> SubLoopExitBlocks;
SuccLoop->getExitBlocks(SubLoopExitBlocks);
for (unsigned i = 0; i < SubLoopExitBlocks.size(); ++i) {
BasicBlock *ExitBB = SubLoopExitBlocks[i];
if (LI->getLoopFor(ExitBB) == L && Visited.insert(ExitBB).second)
VisitStack.push_back(WorklistItem(ExitBB, false));
}
continue;
}
bool IsExitBlock =
std::binary_search(ExitBlocks.begin(), ExitBlocks.end(), SuccBB);
if (IsExitBlock)
continue;
VisitStack.push_back(WorklistItem(SuccBB, false));
}
}
// Place the list of instructions to simplify on the next loop iteration
// into ToSimplify.
std::swap(ToSimplify, Next);
Next->clear();
Changed |= LocalChanged;
} while (LocalChanged);
return Changed;
}
namespace {
class LoopInstSimplifyLegacyPass : public LoopPass {
public:
static char ID; // Pass ID, replacement for typeid
LoopInstSimplifyLegacyPass() : LoopPass(ID) {
initializeLoopInstSimplifyLegacyPassPass(*PassRegistry::getPassRegistry());
}
bool runOnLoop(Loop *L, LPPassManager &LPM) override {
if (skipLoop(L))
return false;
DominatorTreeWrapperPass *DTWP =
getAnalysisIfAvailable<DominatorTreeWrapperPass>();
DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
AssumptionCache *AC =
&getAnalysis<AssumptionCacheTracker>().getAssumptionCache(
*L->getHeader()->getParent());
const TargetLibraryInfo *TLI =
&getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
return SimplifyLoopInst(L, DT, LI, AC, TLI);
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AssumptionCacheTracker>();
AU.addRequired<TargetLibraryInfoWrapperPass>();
AU.setPreservesCFG();
getLoopAnalysisUsage(AU);
}
};
} // end anonymous namespace
PreservedAnalyses LoopInstSimplifyPass::run(Loop &L, LoopAnalysisManager &AM,
LoopStandardAnalysisResults &AR,
LPMUpdater &) {
if (!SimplifyLoopInst(&L, &AR.DT, &AR.LI, &AR.AC, &AR.TLI))
return PreservedAnalyses::all();
auto PA = getLoopPassPreservedAnalyses();
PA.preserveSet<CFGAnalyses>();
return PA;
}
char LoopInstSimplifyLegacyPass::ID = 0;
INITIALIZE_PASS_BEGIN(LoopInstSimplifyLegacyPass, "loop-instsimplify",
"Simplify instructions in loops", false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(LoopPass)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_END(LoopInstSimplifyLegacyPass, "loop-instsimplify",
"Simplify instructions in loops", false, false)
Pass *llvm::createLoopInstSimplifyPass() {
return new LoopInstSimplifyLegacyPass();
}

1
lib/Transforms/Scalar/Scalar.cpp
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@ -61,7 +61,6 @@ void llvm::initializeScalarOpts(PassRegistry &Registry) {
initializeLoopDataPrefetchLegacyPassPass(Registry);
initializeLoopDeletionLegacyPassPass(Registry);
initializeLoopAccessLegacyAnalysisPass(Registry);
initializeLoopInstSimplifyLegacyPassPass(Registry);
initializeLoopInterchangePass(Registry);
initializeLoopPredicationLegacyPassPass(Registry);
initializeLoopRotateLegacyPassPass(Registry);

3
test/Feature/optnone-opt.ll
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@ -3,7 +3,7 @@
; RUN: opt -O2 -S -debug %s 2>&1 | FileCheck %s --check-prefix=OPT-O1 --check-prefix=OPT-O2O3
; RUN: opt -O3 -S -debug %s 2>&1 | FileCheck %s --check-prefix=OPT-O1 --check-prefix=OPT-O2O3
; RUN: opt -dce -die -gvn-hoist -loweratomic -S -debug %s 2>&1 | FileCheck %s --check-prefix=OPT-MORE
; RUN: opt -indvars -licm -loop-deletion -loop-extract -loop-idiom -loop-instsimplify -loop-reduce -loop-reroll -loop-rotate -loop-unroll -loop-unswitch -S -debug %s 2>&1 | FileCheck %s --check-prefix=OPT-LOOP
; RUN: opt -indvars -licm -loop-deletion -loop-extract -loop-idiom -loop-reduce -loop-reroll -loop-rotate -loop-unroll -loop-unswitch -S -debug %s 2>&1 | FileCheck %s --check-prefix=OPT-LOOP
; REQUIRES: asserts
@ -67,6 +67,5 @@ attributes #0 = { optnone noinline }
; OPT-LOOP-DAG: Skipping pass 'Recognize loop idioms'
; OPT-LOOP-DAG: Skipping pass 'Reroll loops'
; OPT-LOOP-DAG: Skipping pass 'Rotate Loops'
; OPT-LOOP-DAG: Skipping pass 'Simplify instructions in loops'
; OPT-LOOP-DAG: Skipping pass 'Unroll loops'
; OPT-LOOP-DAG: Skipping pass 'Unswitch loops'