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Fix a layering violation: hasConstantValue, which is part of the PHINode

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class, uses DominatorTree which is an analysis.  This change moves all of
the tricky hasConstantValue logic to SimplifyInstruction, and replaces it
with a very simple literal implementation.  I already taught users of
hasConstantValue that need tricky stuff to use SimplifyInstruction instead.
I didn't update InlineFunction because the IR looks like it might be in a
funky state at the point it calls hasConstantValue, which makes calling
SimplifyInstruction dangerous since it can in theory do a lot of tricky
reasoning.  This may be a pessimization, for example in the case where
all phi node operands are either undef or a fixed constant.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119459 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan Sands
2010-11-17 04:30:22 +00:00
parent a0c5244e85
commit ff10341183
4 changed files with 47 additions and 69 deletions
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4
lib/Analysis/Lint.cpp
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@@ -582,7 +582,7 @@ Value *Lint::findValueImpl(Value *V, bool OffsetOk,
BBI = BB->end();
}
} else if (PHINode *PN = dyn_cast<PHINode>(V)) {
if (Value *W = PN->hasConstantValue(DT))
if (Value *W = PN->hasConstantValue())
return findValueImpl(W, OffsetOk, Visited);
} else if (CastInst *CI = dyn_cast<CastInst>(V)) {
if (CI->isNoopCast(TD ? TD->getIntPtrType(V->getContext()) :
@@ -615,7 +615,7 @@ Value *Lint::findValueImpl(Value *V, bool OffsetOk,
// As a last resort, try SimplifyInstruction or constant folding.
if (Instruction *Inst = dyn_cast<Instruction>(V)) {
if (Value *W = SimplifyInstruction(Inst, TD))
if (Value *W = SimplifyInstruction(Inst, TD, DT))
if (W != Inst)
return findValueImpl(W, OffsetOk, Visited);
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {