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Now that we look at all the header PHIs, we need to consider all the header PHIs

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when deciding that the loop has stopped evolving. Fixes miscompile in the gcc
torture testsuite!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142843 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2011-10-24 21:02:38 +00:00
parent 3f3f6b067c
commit 3846163aee
2 changed files with 43 additions and 6 deletions
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20
lib/Analysis/ScalarEvolution.cpp
View File

@ -4844,12 +4844,12 @@ ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
// EvaluateExpression adds non-phi values to the CurrentIterVals map.
DenseMap<Instruction *, Constant *> NextIterVals;
Constant *NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD);
if (NextPHI == CurrentIterVals[PN])
return RetVal = NextPHI; // Stopped evolving!
if (NextPHI == 0)
return 0; // Couldn't evaluate!
NextIterVals[PN] = NextPHI;
bool StoppedEvolving = NextPHI == CurrentIterVals[PN];
// Also evaluate the other PHI nodes. However, we don't get to stop if we
// cease to be able to evaluate one of them or if they stop evolving,
// because that doesn't necessarily prevent us from computing PN.
@ -4858,11 +4858,19 @@ ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
PHINode *PHI = dyn_cast<PHINode>(I->first);
if (!PHI || PHI == PN || PHI->getParent() != Header) continue;
Constant *&NextPHI = NextIterVals[PHI];
if (NextPHI) continue; // Already computed!
Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD);
if (!NextPHI) { // Not already computed.
Value *BEValue = PHI->getIncomingValue(SecondIsBackedge);
NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, TD);
}
if (NextPHI != I->second)
StoppedEvolving = false;
}
// If all entries in CurrentIterVals == NextIterVals then we can stop
// iterating, the loop can't continue to change.
if (StoppedEvolving)
return RetVal = CurrentIterVals[PN];
CurrentIterVals.swap(NextIterVals);
}
}

29
test/Analysis/ScalarEvolution/trip-count11.ll Normal file
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@ -0,0 +1,29 @@
; RUN: opt < %s -analyze -scalar-evolution | 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-S128"
target triple = "x86_64-unknown-linux-gnu"
@foo.a = internal constant [8 x i32] [i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7], align 16
define i32 @foo() nounwind uwtable noinline {
entry:
br label %for.cond
for.cond: ; preds = %for.inc, %entry
%sum.0 = phi i32 [ 0, %entry ], [ %add, %for.inc ]
; CHECK: --> %sum.0 Exits: 28
%i.0 = phi i32 [ 0, %entry ], [ %inc, %for.inc ]
%cmp = icmp ult i32 %i.0, 8
br i1 %cmp, label %for.inc, label %for.end
for.inc: ; preds = %for.cond
%idxprom = sext i32 %i.0 to i64
%arrayidx = getelementptr inbounds [8 x i32]* @foo.a, i64 0, i64 %idxprom
%0 = load i32* %arrayidx, align 4
%add = add nsw i32 %sum.0, %0
%inc = add nsw i32 %i.0, 1
br label %for.cond
for.end: ; preds = %for.cond
ret i32 %sum.0
}