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[LIR] Allow merging of memsets in negatively strided loops.

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Last part of PR25166.

llvm-svn: 260732
This commit is contained in:
Chad Rosier 2016-02-12 21:03:23 +00:00
parent c576113aad
commit 926854dd2a
2 changed files with 40 additions and 5 deletions
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12
lib/Transforms/Scalar/LoopIdiomRecognize.cpp
View File

@ -642,11 +642,12 @@ bool LoopIdiomRecognize::processLoopMemSet(MemSetInst *MSI,
// Check to see if the stride matches the size of the memset. If so, then we
// know that every byte is touched in the loop.
const SCEVConstant *Stride = dyn_cast<SCEVConstant>(Ev->getOperand(1));
const SCEVConstant *ConstStride = dyn_cast<SCEVConstant>(Ev->getOperand(1));
if (!ConstStride)
return false;
// TODO: Could also handle negative stride here someday, that will require the
// validity check in mayLoopAccessLocation to be updated though.
if (!Stride || MSI->getLength() != Stride->getValue())
APInt Stride = ConstStride->getAPInt();
if (SizeInBytes != Stride && SizeInBytes != -Stride)
return false;
// Verify that the memset value is loop invariant. If not, we can't promote
@ -657,9 +658,10 @@ bool LoopIdiomRecognize::processLoopMemSet(MemSetInst *MSI,
SmallPtrSet<Instruction *, 1> MSIs;
MSIs.insert(MSI);
bool NegStride = SizeInBytes == -Stride;
return processLoopStridedStore(Pointer, (unsigned)SizeInBytes,
MSI->getAlignment(), SplatValue, MSI, MSIs, Ev,
BECount, /*NegStride=*/false);
BECount, NegStride);
}
/// mayLoopAccessLocation - Return true if the specified loop might access the

33
test/Transforms/LoopIdiom/basic.ll
View File

@ -531,3 +531,36 @@ for.cond.cleanup: ; preds = %for.body
; CHECK: call void @llvm.memcpy
; CHECK: ret
}
; Two dimensional nested loop with negative stride should be promoted to one big memset.
define void @test19(i8* nocapture %X) {
entry:
br label %for.cond1.preheader
for.cond1.preheader: ; preds = %entry, %for.inc4
%i.06 = phi i32 [ 99, %entry ], [ %dec5, %for.inc4 ]
%mul = mul nsw i32 %i.06, 100
br label %for.body3
for.body3: ; preds = %for.cond1.preheader, %for.body3
%j.05 = phi i32 [ 99, %for.cond1.preheader ], [ %dec, %for.body3 ]
%add = add nsw i32 %j.05, %mul
%idxprom = sext i32 %add to i64
%arrayidx = getelementptr inbounds i8, i8* %X, i64 %idxprom
store i8 0, i8* %arrayidx, align 1
%dec = add nsw i32 %j.05, -1
%cmp2 = icmp sgt i32 %j.05, 0
br i1 %cmp2, label %for.body3, label %for.inc4
for.inc4: ; preds = %for.body3
%dec5 = add nsw i32 %i.06, -1
%cmp = icmp sgt i32 %i.06, 0
br i1 %cmp, label %for.cond1.preheader, label %for.end6
for.end6: ; preds = %for.inc4
ret void
; CHECK-LABEL: @test19(
; CHECK: entry:
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* %X, i8 0, i64 10000, i32 1, i1 false)
; CHECK: ret void
}