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LoopRotate: Don't walk the uses of a Constant

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LoopRotate wanted to avoid live range interference by looking at the
uses of a Value in the loop latch and seeing if any lied outside of the
loop.  We would wrongly perform this operation on Constants.

This fixes PR22337.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@227171 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Majnemer 2015-01-27 06:21:43 +00:00
parent d70090ce24
commit 90c42ddc62
2 changed files with 32 additions and 11 deletions
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19
lib/Transforms/Scalar/LoopRotation.cpp
View File

@ -229,20 +229,17 @@ static bool shouldSpeculateInstrs(BasicBlock::iterator Begin,
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr: {
Value *IVOpnd = nullptr;
if (isa<ConstantInt>(I->getOperand(0)))
IVOpnd = I->getOperand(1);
if (isa<ConstantInt>(I->getOperand(1))) {
if (IVOpnd)
return false;
IVOpnd = I->getOperand(0);
}
Value *IVOpnd = !isa<Constant>(I->getOperand(0))
? I->getOperand(0)
: !isa<Constant>(I->getOperand(1))
? I->getOperand(1)
: nullptr;
if (!IVOpnd)
return false;
// If increment operand is used outside of the loop, this speculation
// could cause extra live range interference.
if (MultiExitLoop && IVOpnd) {
if (MultiExitLoop) {
for (User *UseI : IVOpnd->users()) {
auto *UserInst = cast<Instruction>(UseI);
if (!L->contains(UserInst))

24
test/Transforms/LoopRotate/pr22337.ll Normal file
View File

@ -0,0 +1,24 @@
; RUN: opt < %s -loop-rotate -S | FileCheck %s
@a = external global i8, align 4
@tmp = global i8* @a
define void @f() {
; CHECK-LABEL: define void @f(
; CHECK: getelementptr i8* @a, i32 0
entry:
br label %for.preheader
for.preheader:
br i1 undef, label %if.then8, label %for.body
for.body:
br i1 undef, label %if.end, label %if.then8
if.end:
%arrayidx = getelementptr i8* @a, i32 0
br label %for.preheader
if.then8:
unreachable
}