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Protect ChangeCompareStride from situations in which it is possible 

for it to generate use-before-def IR, such as in this testcase.

llvm-svn: 52258
This commit is contained in:
Dan Gohman 2008-06-13 21:43:41 +00:00
parent 9833a1b407
commit 9ad8c54aab
2 changed files with 32 additions and 3 deletions
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15
llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
View File

@ -1529,6 +1529,15 @@ namespace {
ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
IVStrideUse* &CondUse,
const SCEVHandle* &CondStride) {
// Forgo this transformation if the condition has multiple uses. This is
// over-conservative, but simpler than alternatives. It guards against
// comparisons with a use that occurs earlier than the add instruction for the
// new stride index. See
// test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness.ll
// for an example of this situation.
if (!Cond->hasOneUse())
return Cond;
if (StrideOrder.size() < 2 ||
IVUsesByStride[*CondStride].Users.size() != 1)
return Cond;
@ -1654,9 +1663,9 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond,
RHS = SCEVExpander::InsertCastOfTo(Instruction::IntToPtr, RHS, NewCmpTy);
}
// Insert new compare instruction.
Cond = new ICmpInst(Predicate, NewIncV, RHS);
Cond->setName(L->getHeader()->getName() + ".termcond");
OldCond->getParent()->getInstList().insert(OldCond, Cond);
Cond = new ICmpInst(Predicate, NewIncV, RHS,
L->getHeader()->getName() + ".termcond",
OldCond);
// Remove the old compare instruction. The old indvar is probably dead too.
DeadInsts.insert(cast<Instruction>(CondUse->OperandValToReplace));

20
llvm/test/Transforms/LoopStrengthReduce/change-compare-stride-trickiness.ll Normal file
View File

@ -0,0 +1,20 @@
; RUN: llvm-as < %s | llc
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-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128"
target triple = "x86_64-apple-darwin9"
define void @foo() {
entry:
br label %loop
loop:
%indvar = phi i32 [ 0, %entry ], [ %i.2.0.us1534, %loop ] ; <i32> [#uses=1]
%i.2.0.us1534 = add i32 %indvar, 1 ; <i32> [#uses=3]
%tmp611.us1535 = icmp eq i32 %i.2.0.us1534, 4 ; <i1> [#uses=2]
%tmp623.us1538 = select i1 %tmp611.us1535, i32 6, i32 0 ; <i32> [#uses=0]
%tmp628.us1540 = shl i32 %i.2.0.us1534, 1 ; <i32> [#uses=1]
%tmp645646647.us1547 = sext i32 %tmp628.us1540 to i64 ; <i64> [#uses=0]
br i1 %tmp611.us1535, label %exit, label %loop
exit:
ret void
}