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fix PR5837 by having SSAUpdate reuse phi nodes for the

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'GetValueInMiddleOfBlock' case, instead of inserting 
duplicates.

A similar fix is almost certainly needed by the machine-level
SSAUpdate implementation.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91820 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2009-12-21 07:16:11 +00:00
parent 6a363782fe
commit 4c1e3da0cd
2 changed files with 58 additions and 1 deletions
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24
lib/Transforms/Utils/SSAUpdater.cpp
View File

@ -149,7 +149,29 @@ Value *SSAUpdater::GetValueInMiddleOfBlock(BasicBlock *BB) {
if (SingularValue != 0)
return SingularValue;
// Otherwise, we do need a PHI: insert one now.
// Otherwise, we do need a PHI: check to see if we already have one available
// in this block that produces the right value.
if (isa<PHINode>(BB->begin())) {
DenseMap<BasicBlock*, Value*> ValueMapping(PredValues.begin(),
PredValues.end());
PHINode *SomePHI;
for (BasicBlock::iterator It = BB->begin();
(SomePHI = dyn_cast<PHINode>(It)); ++It) {
// Scan this phi to see if it is what we need.
bool Equal = true;
for (unsigned i = 0, e = SomePHI->getNumIncomingValues(); i != e; ++i)
if (ValueMapping[SomePHI->getIncomingBlock(i)] !=
SomePHI->getIncomingValue(i)) {
Equal = false;
break;
}
if (Equal)
return SomePHI;
}
}
// Ok, we have no way out, insert a new one now.
PHINode *InsertedPHI = PHINode::Create(PrototypeValue->getType(),
PrototypeValue->getName(),
&BB->front());

35
test/Transforms/LoopRotate/phi-duplicate.ll Normal file
View File

@ -0,0 +1,35 @@
; RUN: opt -S %s -loop-rotate | 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-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin10.0"
; PR5837
define void @test(i32 %N, double* %G) nounwind ssp {
entry:
br label %for.cond
for.cond: ; preds = %for.body, %entry
%j.0 = phi i64 [ 1, %entry ], [ %inc, %for.body ] ; <i64> [#uses=5]
%cmp = icmp slt i64 %j.0, 1000 ; <i1> [#uses=1]
br i1 %cmp, label %for.body, label %for.end
for.body: ; preds = %for.cond
%arrayidx = getelementptr inbounds double* %G, i64 %j.0 ; <double*> [#uses=1]
%tmp3 = load double* %arrayidx ; <double> [#uses=1]
%sub = sub i64 %j.0, 1 ; <i64> [#uses=1]
%arrayidx6 = getelementptr inbounds double* %G, i64 %sub ; <double*> [#uses=1]
%tmp7 = load double* %arrayidx6 ; <double> [#uses=1]
%add = fadd double %tmp3, %tmp7 ; <double> [#uses=1]
%arrayidx10 = getelementptr inbounds double* %G, i64 %j.0 ; <double*> [#uses=1]
store double %add, double* %arrayidx10
%inc = add nsw i64 %j.0, 1 ; <i64> [#uses=1]
br label %for.cond
for.end: ; preds = %for.cond
ret void
}
; Should only end up with one phi.
; CHECK: for.body:
; CHECK-NEXT: %j.02 = phi i64
; CHECK-NOT phi
; CHECK: ret void