Use SCEV to avoid inserting some bounds checks.

This patch uses SCEV to avoid inserting some bounds checks when they are not needed.  This slightly improves the performance of code compiled with the bounds check sanitizer.

Differential Revision: https://reviews.llvm.org/D49602

llvm-svn: 337830
This commit is contained in:
Joel Galenson 2018-07-24 15:21:54 +00:00
parent 3241724536
commit 8dbcc58917
2 changed files with 386 additions and 12 deletions

View File

@ -11,6 +11,7 @@
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/TargetFolder.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/BasicBlock.h"
@ -59,8 +60,8 @@ template <typename GetTrapBBT>
static bool instrumentMemAccess(Value *Ptr, Value *InstVal,
const DataLayout &DL, TargetLibraryInfo &TLI,
ObjectSizeOffsetEvaluator &ObjSizeEval,
BuilderTy &IRB,
GetTrapBBT GetTrapBB) {
BuilderTy &IRB, GetTrapBBT GetTrapBB,
ScalarEvolution &SE) {
uint64_t NeededSize = DL.getTypeStoreSize(InstVal->getType());
LLVM_DEBUG(dbgs() << "Instrument " << *Ptr << " for " << Twine(NeededSize)
<< " bytes\n");
@ -79,6 +80,10 @@ static bool instrumentMemAccess(Value *Ptr, Value *InstVal,
Type *IntTy = DL.getIntPtrType(Ptr->getType());
Value *NeededSizeVal = ConstantInt::get(IntTy, NeededSize);
auto SizeRange = SE.getUnsignedRange(SE.getSCEV(Size));
auto OffsetRange = SE.getUnsignedRange(SE.getSCEV(Offset));
auto NeededSizeRange = SE.getUnsignedRange(SE.getSCEV(NeededSizeVal));
// three checks are required to ensure safety:
// . Offset >= 0 (since the offset is given from the base ptr)
// . Size >= Offset (unsigned)
@ -87,10 +92,17 @@ static bool instrumentMemAccess(Value *Ptr, Value *InstVal,
// optimization: if Size >= 0 (signed), skip 1st check
// FIXME: add NSW/NUW here? -- we dont care if the subtraction overflows
Value *ObjSize = IRB.CreateSub(Size, Offset);
Value *Cmp2 = IRB.CreateICmpULT(Size, Offset);
Value *Cmp3 = IRB.CreateICmpULT(ObjSize, NeededSizeVal);
Value *Cmp2 = SizeRange.getUnsignedMin().uge(OffsetRange.getUnsignedMax())
? ConstantInt::getFalse(Ptr->getContext())
: IRB.CreateICmpULT(Size, Offset);
Value *Cmp3 = SizeRange.sub(OffsetRange)
.getUnsignedMin()
.uge(NeededSizeRange.getUnsignedMax())
? ConstantInt::getFalse(Ptr->getContext())
: IRB.CreateICmpULT(ObjSize, NeededSizeVal);
Value *Or = IRB.CreateOr(Cmp2, Cmp3);
if (!SizeCI || SizeCI->getValue().slt(0)) {
if ((!SizeCI || SizeCI->getValue().slt(0)) &&
!SizeRange.getSignedMin().isNonNegative()) {
Value *Cmp1 = IRB.CreateICmpSLT(Offset, ConstantInt::get(IntTy, 0));
Or = IRB.CreateOr(Cmp1, Or);
}
@ -123,7 +135,8 @@ static bool instrumentMemAccess(Value *Ptr, Value *InstVal,
return true;
}
static bool addBoundsChecking(Function &F, TargetLibraryInfo &TLI) {
static bool addBoundsChecking(Function &F, TargetLibraryInfo &TLI,
ScalarEvolution &SE) {
const DataLayout &DL = F.getParent()->getDataLayout();
ObjectSizeOffsetEvaluator ObjSizeEval(DL, &TLI, F.getContext(),
/*RoundToAlign=*/true);
@ -168,19 +181,19 @@ static bool addBoundsChecking(Function &F, TargetLibraryInfo &TLI) {
BuilderTy IRB(Inst->getParent(), BasicBlock::iterator(Inst), TargetFolder(DL));
if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
MadeChange |= instrumentMemAccess(LI->getPointerOperand(), LI, DL, TLI,
ObjSizeEval, IRB, GetTrapBB);
ObjSizeEval, IRB, GetTrapBB, SE);
} else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
MadeChange |=
instrumentMemAccess(SI->getPointerOperand(), SI->getValueOperand(),
DL, TLI, ObjSizeEval, IRB, GetTrapBB);
DL, TLI, ObjSizeEval, IRB, GetTrapBB, SE);
} else if (AtomicCmpXchgInst *AI = dyn_cast<AtomicCmpXchgInst>(Inst)) {
MadeChange |=
instrumentMemAccess(AI->getPointerOperand(), AI->getCompareOperand(),
DL, TLI, ObjSizeEval, IRB, GetTrapBB);
DL, TLI, ObjSizeEval, IRB, GetTrapBB, SE);
} else if (AtomicRMWInst *AI = dyn_cast<AtomicRMWInst>(Inst)) {
MadeChange |=
instrumentMemAccess(AI->getPointerOperand(), AI->getValOperand(), DL,
TLI, ObjSizeEval, IRB, GetTrapBB);
TLI, ObjSizeEval, IRB, GetTrapBB, SE);
} else {
llvm_unreachable("unknown Instruction type");
}
@ -190,8 +203,9 @@ static bool addBoundsChecking(Function &F, TargetLibraryInfo &TLI) {
PreservedAnalyses BoundsCheckingPass::run(Function &F, FunctionAnalysisManager &AM) {
auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
auto &SE = AM.getResult<ScalarEvolutionAnalysis>(F);
if (!addBoundsChecking(F, TLI))
if (!addBoundsChecking(F, TLI, SE))
return PreservedAnalyses::all();
return PreservedAnalyses::none();
@ -207,11 +221,13 @@ struct BoundsCheckingLegacyPass : public FunctionPass {
bool runOnFunction(Function &F) override {
auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
return addBoundsChecking(F, TLI);
auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
return addBoundsChecking(F, TLI, SE);
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<TargetLibraryInfoWrapperPass>();
AU.addRequired<ScalarEvolutionWrapperPass>();
}
};
} // namespace

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@ -0,0 +1,358 @@
; RUN: opt < %s -bounds-checking -S | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
; CHECK-LABEL: @sumSize
define dso_local i32 @sumSize(i32 %n) {
entry:
%foo = alloca [1000 x i32], align 16
%0 = bitcast [1000 x i32]* %foo to i8*
call void @llvm.lifetime.start.p0i8(i64 4000, i8* nonnull %0)
%arraydecay = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 0
call void @fill(i32* nonnull %arraydecay, i32 %n)
br label %for.body.i
for.body.i: ; preds = %for.body.i, %entry
%indvars.iv.i = phi i64 [ 0, %entry ], [ %indvars.iv.next.i, %for.body.i ]
%sum.07.i = phi i32 [ 0, %entry ], [ %add.i, %for.body.i ]
%arrayidx.i = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 %indvars.iv.i
; CHECK-NOT: trap
%1 = load i32, i32* %arrayidx.i, align 4
%add.i = add nsw i32 %1, %sum.07.i
%indvars.iv.next.i = add nuw nsw i64 %indvars.iv.i, 1
%exitcond.i = icmp eq i64 %indvars.iv.next.i, 1000
br i1 %exitcond.i, label %accumulate.exit, label %for.body.i
accumulate.exit: ; preds = %for.body.i
call void @llvm.lifetime.end.p0i8(i64 4000, i8* nonnull %0)
ret i32 %add.i
}
declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
declare dso_local void @fill(i32*, i32)
declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture)
; CHECK-LABEL: @sumSizePlusOne
define dso_local i32 @sumSizePlusOne(i32 %n) {
entry:
%foo = alloca [1000 x i32], align 16
%0 = bitcast [1000 x i32]* %foo to i8*
call void @llvm.lifetime.start.p0i8(i64 4000, i8* nonnull %0)
%arraydecay = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 0
call void @fill(i32* nonnull %arraydecay, i32 %n)
br label %for.body.i
for.body.i: ; preds = %for.body.i, %entry
%indvars.iv.i = phi i64 [ 0, %entry ], [ %indvars.iv.next.i, %for.body.i ]
%sum.01.i = phi i32 [ 0, %entry ], [ %add.i, %for.body.i ]
%arrayidx.i = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 %indvars.iv.i
; CHECK: mul i64 {{.*}}, 4
; CHECK: sub i64 4000, %
; CHECK-NEXT: icmp ult i64 {{.*}}, 4
; CHECK-NEXT: or i1
; CHECK: trap
%1 = load i32, i32* %arrayidx.i, align 4
%add.i = add nsw i32 %1, %sum.01.i
%indvars.iv.next.i = add nuw nsw i64 %indvars.iv.i, 1
%exitcond.i = icmp eq i64 %indvars.iv.next.i, 1001
br i1 %exitcond.i, label %accumulate.exit, label %for.body.i
accumulate.exit: ; preds = %for.body.i
call void @llvm.lifetime.end.p0i8(i64 4000, i8* nonnull %0)
ret i32 %add.i
}
; CHECK-LABEL: @sumLarger
define dso_local i32 @sumLarger(i32 %n) {
entry:
%foo = alloca [1000 x i32], align 16
%0 = bitcast [1000 x i32]* %foo to i8*
call void @llvm.lifetime.start.p0i8(i64 4000, i8* nonnull %0)
%arraydecay = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 0
call void @fill(i32* nonnull %arraydecay, i32 %n)
br label %for.body.i
for.body.i: ; preds = %for.body.i, %entry
%indvars.iv.i = phi i64 [ 0, %entry ], [ %indvars.iv.next.i, %for.body.i ]
%sum.07.i = phi i32 [ 0, %entry ], [ %add.i, %for.body.i ]
%arrayidx.i = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 %indvars.iv.i
; CHECK: mul i64 {{.*}}, 4
; CHECK: sub i64 4000, %
; CHECK-NEXT: icmp ult i64 4000, %
; CHECK-NEXT: icmp ult i64 {{.*}}, 4
; CHECK-NEXT: or i1
; CHECK: trap
%1 = load i32, i32* %arrayidx.i, align 4
%add.i = add nsw i32 %1, %sum.07.i
%indvars.iv.next.i = add nuw nsw i64 %indvars.iv.i, 1
%exitcond.i = icmp eq i64 %indvars.iv.next.i, 2000
br i1 %exitcond.i, label %accumulate.exit, label %for.body.i
accumulate.exit: ; preds = %for.body.i
call void @llvm.lifetime.end.p0i8(i64 4000, i8* nonnull %0)
ret i32 %add.i
}
; CHECK-LABEL: @sumUnknown
define dso_local i32 @sumUnknown(i32 %n) {
entry:
%foo = alloca [1000 x i32], align 16
%0 = bitcast [1000 x i32]* %foo to i8*
call void @llvm.lifetime.start.p0i8(i64 4000, i8* nonnull %0)
%arraydecay = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 0
call void @fill(i32* nonnull %arraydecay, i32 %n)
%cmp6.i = icmp eq i32 %n, 0
br i1 %cmp6.i, label %accumulate.exit, label %for.body.preheader.i
for.body.preheader.i: ; preds = %entry
%wide.trip.count.i = zext i32 %n to i64
br label %for.body.i
for.body.i: ; preds = %for.body.i, %for.body.preheader.i
%indvars.iv.i = phi i64 [ 0, %for.body.preheader.i ], [ %indvars.iv.next.i, %for.body.i ]
%sum.07.i = phi i32 [ 0, %for.body.preheader.i ], [ %add.i, %for.body.i ]
%arrayidx.i = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 %indvars.iv.i
; CHECK: mul i64 {{.*}}, 4
; CHECK: sub i64 4000, %
; CHECK-NEXT: icmp ult i64 4000, %
; CHECK-NEXT: icmp ult i64 {{.*}}, 4
; CHECK-NEXT: or i1
; CHECK: trap
%1 = load i32, i32* %arrayidx.i, align 4
%add.i = add nsw i32 %1, %sum.07.i
%indvars.iv.next.i = add nuw nsw i64 %indvars.iv.i, 1
%exitcond.i = icmp eq i64 %indvars.iv.next.i, %wide.trip.count.i
br i1 %exitcond.i, label %accumulate.exit, label %for.body.i
accumulate.exit: ; preds = %for.body.i, %entry
%sum.0.lcssa.i = phi i32 [ 0, %entry ], [ %add.i, %for.body.i ]
call void @llvm.lifetime.end.p0i8(i64 4000, i8* nonnull %0)
ret i32 %sum.0.lcssa.i
}
; CHECK-LABEL: @twoDimSize
define dso_local i32 @twoDimSize(i32 %n) {
entry:
%foo = alloca [2 x [2 x i32]], align 16
%0 = bitcast [2 x [2 x i32]]* %foo to i8*
call void @llvm.lifetime.start.p0i8(i64 16, i8* nonnull %0)
%arraydecay = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %foo, i64 0, i64 0, i64 0
call void @fill(i32* nonnull %arraydecay, i32 %n)
br label %for.cond1.preheader
for.cond1.preheader: ; preds = %for.cond.cleanup3, %entry
%indvars.iv23 = phi i64 [ 0, %entry ], [ %indvars.iv.next24, %for.cond.cleanup3 ]
%sum.021 = phi i32 [ 0, %entry ], [ %add, %for.cond.cleanup3 ]
br label %for.body4
for.cond.cleanup: ; preds = %for.cond.cleanup3
call void @llvm.lifetime.end.p0i8(i64 16, i8* nonnull %0)
ret i32 %add
for.cond.cleanup3: ; preds = %for.body4
%indvars.iv.next24 = add nuw nsw i64 %indvars.iv23, 1
%exitcond25 = icmp eq i64 %indvars.iv.next24, 2
br i1 %exitcond25, label %for.cond.cleanup, label %for.cond1.preheader
for.body4: ; preds = %for.body4, %for.cond1.preheader
%indvars.iv = phi i64 [ 0, %for.cond1.preheader ], [ %indvars.iv.next, %for.body4 ]
%sum.119 = phi i32 [ %sum.021, %for.cond1.preheader ], [ %add, %for.body4 ]
%arrayidx7 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %foo, i64 0, i64 %indvars.iv23, i64 %indvars.iv
; CHECK-NOT: trap
%1 = load i32, i32* %arrayidx7, align 4
%add = add nsw i32 %1, %sum.119
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%exitcond = icmp eq i64 %indvars.iv.next, 2
br i1 %exitcond, label %for.cond.cleanup3, label %for.body4
}
; CHECK-LABEL: @twoDimLarger1
define dso_local i32 @twoDimLarger1(i32 %n) {
entry:
%foo = alloca [2 x [2 x i32]], align 16
%0 = bitcast [2 x [2 x i32]]* %foo to i8*
call void @llvm.lifetime.start.p0i8(i64 16, i8* nonnull %0)
%arraydecay = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %foo, i64 0, i64 0, i64 0
call void @fill(i32* nonnull %arraydecay, i32 %n)
br label %for.cond1.preheader
for.cond1.preheader: ; preds = %for.cond.cleanup3, %entry
%indvars.iv23 = phi i64 [ 0, %entry ], [ %indvars.iv.next24, %for.cond.cleanup3 ]
%sum.021 = phi i32 [ 0, %entry ], [ %add, %for.cond.cleanup3 ]
br label %for.body4
for.cond.cleanup: ; preds = %for.cond.cleanup3
call void @llvm.lifetime.end.p0i8(i64 16, i8* nonnull %0)
ret i32 %add
for.cond.cleanup3: ; preds = %for.body4
%indvars.iv.next24 = add nuw nsw i64 %indvars.iv23, 1
%exitcond25 = icmp eq i64 %indvars.iv.next24, 3
br i1 %exitcond25, label %for.cond.cleanup, label %for.cond1.preheader
for.body4: ; preds = %for.body4, %for.cond1.preheader
%indvars.iv = phi i64 [ 0, %for.cond1.preheader ], [ %indvars.iv.next, %for.body4 ]
%sum.119 = phi i32 [ %sum.021, %for.cond1.preheader ], [ %add, %for.body4 ]
%arrayidx7 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %foo, i64 0, i64 %indvars.iv23, i64 %indvars.iv
; CHECK: mul i64 {{.*}}, 8
; CHECK: mul i64 {{.*}}, 4
; CHECK: add i64
; CHECK: sub i64 16, %
; CHECK-NEXT: icmp ult i64 16, %
; CHECK-NEXT: icmp ult i64 {{.*}}, 4
; CHECK-NEXT: or i1
; CHECK: trap
%1 = load i32, i32* %arrayidx7, align 4
%add = add nsw i32 %1, %sum.119
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%exitcond = icmp eq i64 %indvars.iv.next, 2
br i1 %exitcond, label %for.cond.cleanup3, label %for.body4
}
; CHECK-LABEL: @twoDimLarger2
define dso_local i32 @twoDimLarger2(i32 %n) {
entry:
%foo = alloca [2 x [2 x i32]], align 16
%0 = bitcast [2 x [2 x i32]]* %foo to i8*
call void @llvm.lifetime.start.p0i8(i64 16, i8* nonnull %0)
%arraydecay = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %foo, i64 0, i64 0, i64 0
call void @fill(i32* nonnull %arraydecay, i32 %n)
br label %for.cond1.preheader
for.cond1.preheader: ; preds = %for.cond.cleanup3, %entry
%indvars.iv23 = phi i64 [ 0, %entry ], [ %indvars.iv.next24, %for.cond.cleanup3 ]
%sum.021 = phi i32 [ 0, %entry ], [ %add, %for.cond.cleanup3 ]
br label %for.body4
for.cond.cleanup: ; preds = %for.cond.cleanup3
call void @llvm.lifetime.end.p0i8(i64 16, i8* nonnull %0)
ret i32 %add
for.cond.cleanup3: ; preds = %for.body4
%indvars.iv.next24 = add nuw nsw i64 %indvars.iv23, 1
%exitcond25 = icmp eq i64 %indvars.iv.next24, 2
br i1 %exitcond25, label %for.cond.cleanup, label %for.cond1.preheader
for.body4: ; preds = %for.body4, %for.cond1.preheader
%indvars.iv = phi i64 [ 0, %for.cond1.preheader ], [ %indvars.iv.next, %for.body4 ]
%sum.119 = phi i32 [ %sum.021, %for.cond1.preheader ], [ %add, %for.body4 ]
%arrayidx7 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %foo, i64 0, i64 %indvars.iv23, i64 %indvars.iv
; CHECK: mul i64 {{.*}}, 8
; CHECK: mul i64 {{.*}}, 4
; CHECK: add i64
; CHECK: sub i64 16, %
; CHECK-NEXT: icmp ult i64 {{.*}}, 4
; CHECK-NEXT: or i1
; CHECK: trap
%1 = load i32, i32* %arrayidx7, align 4
%add = add nsw i32 %1, %sum.119
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%exitcond = icmp eq i64 %indvars.iv.next, 3
br i1 %exitcond, label %for.cond.cleanup3, label %for.body4
}
; CHECK-LABEL: @twoDimUnknown
define dso_local i32 @twoDimUnknown(i32 %n) {
entry:
%foo = alloca [2 x [2 x i32]], align 16
%0 = bitcast [2 x [2 x i32]]* %foo to i8*
call void @llvm.lifetime.start.p0i8(i64 16, i8* nonnull %0)
%arraydecay = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %foo, i64 0, i64 0, i64 0
call void @fill(i32* nonnull %arraydecay, i32 %n)
%cmp24 = icmp eq i32 %n, 0
br i1 %cmp24, label %for.cond.cleanup, label %for.cond1.preheader.lr.ph
for.cond1.preheader.lr.ph: ; preds = %entry
%wide.trip.count = zext i32 %n to i64
%wide.trip.count.le = zext i32 %n to i64
br label %for.body4.lr.ph
for.body4.lr.ph: ; preds = %for.cond1.preheader.lr.ph, %for.cond.cleanup3
%indvars.iv28 = phi i64 [ 0, %for.cond1.preheader.lr.ph ], [ %indvars.iv.next29, %for.cond.cleanup3 ]
%sum.025 = phi i32 [ 0, %for.cond1.preheader.lr.ph ], [ %add, %for.cond.cleanup3 ]
br label %for.body4
for.cond.cleanup: ; preds = %for.cond.cleanup3, %entry
%sum.0.lcssa = phi i32 [ 0, %entry ], [ %add, %for.cond.cleanup3 ]
call void @llvm.lifetime.end.p0i8(i64 16, i8* nonnull %0)
ret i32 %sum.0.lcssa
for.cond.cleanup3: ; preds = %for.body4
%indvars.iv.next29 = add nuw nsw i64 %indvars.iv28, 1
%exitcond31 = icmp eq i64 %indvars.iv.next29, %wide.trip.count.le
br i1 %exitcond31, label %for.cond.cleanup, label %for.body4.lr.ph
for.body4: ; preds = %for.body4, %for.body4.lr.ph
%indvars.iv = phi i64 [ 0, %for.body4.lr.ph ], [ %indvars.iv.next, %for.body4 ]
%sum.122 = phi i32 [ %sum.025, %for.body4.lr.ph ], [ %add, %for.body4 ]
%arrayidx7 = getelementptr inbounds [2 x [2 x i32]], [2 x [2 x i32]]* %foo, i64 0, i64 %indvars.iv28, i64 %indvars.iv
; CHECK: mul i64 {{.*}}, 8
; CHECK: mul i64 {{.*}}, 4
; CHECK: add i64
; CHECK: sub i64 16, %
; CHECK-NEXT: icmp ult i64 16, %
; CHECK-NEXT: icmp ult i64 {{.*}}, 4
; CHECK-NEXT: or i1
; CHECK: trap
%1 = load i32, i32* %arrayidx7, align 4
%add = add nsw i32 %1, %sum.122
%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
%exitcond = icmp eq i64 %indvars.iv.next, %wide.trip.count
br i1 %exitcond, label %for.cond.cleanup3, label %for.body4
}
; CHECK-LABEL: @countDownGood
define dso_local i32 @countDownGood(i32 %n) {
entry:
%foo = alloca [1000 x i32], align 16
%0 = bitcast [1000 x i32]* %foo to i8*
call void @llvm.lifetime.start.p0i8(i64 4000, i8* nonnull %0)
%arraydecay = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 0
call void @fill(i32* nonnull %arraydecay, i32 %n)
br label %for.body
for.cond.cleanup: ; preds = %for.body
call void @llvm.lifetime.end.p0i8(i64 4000, i8* nonnull %0)
ret i32 %add
for.body: ; preds = %for.body, %entry
%indvars.iv = phi i64 [ 999, %entry ], [ %indvars.iv.next, %for.body ]
%sum.06 = phi i32 [ 0, %entry ], [ %add, %for.body ]
%arrayidx = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 %indvars.iv
; CHECK-NOT: trap
%1 = load i32, i32* %arrayidx, align 4
%add = add nsw i32 %1, %sum.06
%indvars.iv.next = add nsw i64 %indvars.iv, -1
%cmp = icmp eq i64 %indvars.iv, 0
br i1 %cmp, label %for.cond.cleanup, label %for.body
}
; CHECK-LABEL: @countDownBad
define dso_local i32 @countDownBad(i32 %n) {
entry:
%foo = alloca [1000 x i32], align 16
%0 = bitcast [1000 x i32]* %foo to i8*
call void @llvm.lifetime.start.p0i8(i64 4000, i8* nonnull %0)
%arraydecay = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 0
call void @fill(i32* nonnull %arraydecay, i32 %n)
br label %for.body
for.cond.cleanup: ; preds = %for.body
call void @llvm.lifetime.end.p0i8(i64 4000, i8* nonnull %0)
ret i32 %add
for.body: ; preds = %entry, %for.body
%indvars.iv = phi i64 [ 999, %entry ], [ %indvars.iv.next, %for.body ]
%sum.06 = phi i32 [ 0, %entry ], [ %add, %for.body ]
%arrayidx = getelementptr inbounds [1000 x i32], [1000 x i32]* %foo, i64 0, i64 %indvars.iv
; CHECK: mul i64 {{.*}}, 4
; CHECK: sub i64 4000, %
; CHECK-NEXT: icmp ult i64 4000, %
; CHECK: trap
%1 = load i32, i32* %arrayidx, align 4
%add = add nsw i32 %1, %sum.06
%indvars.iv.next = add nsw i64 %indvars.iv, -1
%cmp = icmp sgt i64 %indvars.iv, -1
br i1 %cmp, label %for.body, label %for.cond.cleanup
}