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getSmallConstantTripMultiple should never return zero.

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When the trip count is -1, getSmallConstantTripMultiple could return zero,
and this would cause runtime loop unrolling to assert. Instead of returning
zero, one is now returned (consistent with the existing overflow cases).
Fixes PR14167.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166612 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Hal Finkel 2012-10-24 19:46:44 +00:00
parent 99abc17832
commit 8c65549318
2 changed files with 49 additions and 2 deletions
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7
lib/Analysis/ScalarEvolution.cpp
View File

@ -3979,8 +3979,11 @@ getSmallConstantTripMultiple(Loop *L, BasicBlock *ExitingBlock) {
ConstantInt *Result = MulC->getValue();
// Guard against huge trip counts.
if (!Result || Result->getValue().getActiveBits() > 32)
// Guard against huge trip counts (this requires checking
// for zero to handle the case where the trip count == -1 and the
// addition wraps).
if (!Result || Result->getValue().getActiveBits() > 32 ||
Result->getValue().getActiveBits() == 0)
return 1;
return (unsigned)Result->getZExtValue();

44
test/Transforms/LoopUnroll/pr14167.ll Normal file
View File

@ -0,0 +1,44 @@
; RUN: opt < %s -S -loop-unroll -unroll-runtime | FileCheck %s
target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v128:128:128-n32:64"
target triple = "powerpc64-bgq-linux"
define void @test1() nounwind {
; Ensure that we don't crash when the trip count == -1.
; CHECK: @test1
entry:
br label %for.cond2.preheader
for.cond2.preheader: ; preds = %for.end, %entry
br i1 false, label %middle.block, label %vector.ph
vector.ph: ; preds = %for.cond2.preheader
br label %vector.body
vector.body: ; preds = %vector.body, %vector.ph
br i1 undef, label %middle.block.loopexit, label %vector.body
middle.block.loopexit: ; preds = %vector.body
br label %middle.block
middle.block: ; preds = %middle.block.loopexit, %for.cond2.preheader
br i1 true, label %for.end, label %scalar.preheader
scalar.preheader: ; preds = %middle.block
br label %for.body4
for.body4: ; preds = %for.body4, %scalar.preheader
%indvars.iv = phi i64 [ 16000, %scalar.preheader ], [ %indvars.iv.next, %for.body4 ]
%indvars.iv.next = add i64 %indvars.iv, 1
%lftr.wideiv = trunc i64 %indvars.iv.next to i32
%exitcond = icmp ne i32 %lftr.wideiv, 16000
br i1 %exitcond, label %for.body4, label %for.end.loopexit
for.end.loopexit: ; preds = %for.body4
br label %for.end
for.end: ; preds = %for.end.loopexit, %middle.block
br i1 undef, label %for.cond2.preheader, label %for.end15
for.end15: ; preds = %for.end
ret void
}