Enhance the previous fix for PR4895 to allow more values than just
simple constants for the true/false value of the select. We now
do phi translation etc. This really fixes PR4895 :)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82917 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index be88d29..aec9027 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -1949,9 +1949,9 @@
// Check to see if all of the operands of the PHI are simple constants
// (constantint/constantfp/undef). If there is one non-constant value,
- // remember the BB it is. If there is more than one or if *it* is a PHI, bail
- // out. We don't do arbitrary constant expressions here because moving their
- // computation can be expensive without a cost model.
+ // remember the BB it is in. If there is more than one or if *it* is a PHI,
+ // bail out. We don't do arbitrary constant expressions here because moving
+ // their computation can be expensive without a cost model.
BasicBlock *NonConstBB = 0;
for (unsigned i = 0; i != NumPHIValues; ++i)
if (!isa<Constant>(PN->getIncomingValue(i)) ||
@@ -1985,21 +1985,23 @@
if (SelectInst *SI = dyn_cast<SelectInst>(&I)) {
// We only currently try to fold the condition of a select when it is a phi,
// not the true/false values.
+ Value *TrueV = SI->getTrueValue();
+ Value *FalseV = SI->getFalseValue();
for (unsigned i = 0; i != NumPHIValues; ++i) {
+ BasicBlock *ThisBB = PN->getIncomingBlock(i);
+ Value *TrueVInPred = TrueV->DoPHITranslation(I.getParent(), ThisBB);
+ Value *FalseVInPred = FalseV->DoPHITranslation(I.getParent(), ThisBB);
Value *InV = 0;
if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) {
- if (InC->isNullValue())
- InV = SI->getFalseValue();
- else
- InV = SI->getTrueValue();
+ InV = InC->isNullValue() ? FalseVInPred : TrueVInPred;
} else {
assert(PN->getIncomingBlock(i) == NonConstBB);
- InV = SelectInst::Create(PN->getIncomingValue(i),
- SI->getTrueValue(), SI->getFalseValue(),
+ InV = SelectInst::Create(PN->getIncomingValue(i), TrueVInPred,
+ FalseVInPred,
"phitmp", NonConstBB->getTerminator());
Worklist.Add(cast<Instruction>(InV));
}
- NewPN->addIncoming(InV, PN->getIncomingBlock(i));
+ NewPN->addIncoming(InV, ThisBB);
}
} else if (I.getNumOperands() == 2) {
Constant *C = cast<Constant>(I.getOperand(1));
@@ -9234,6 +9236,14 @@
return Changed ? &SI : 0;
}
+/// isDefinedInBB - Return true if the value is an instruction defined in the
+/// specified basicblock.
+static bool isDefinedInBB(const Value *V, const BasicBlock *BB) {
+ const Instruction *I = dyn_cast<Instruction>(V);
+ return I != 0 && I->getParent() == BB;
+}
+
+
Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
Value *CondVal = SI.getCondition();
Value *TrueVal = SI.getTrueValue();
@@ -9446,10 +9456,13 @@
}
// See if we can fold the select into a phi node. The true/false values have
- // to be live in the predecessor blocks.
+ // to be live in the predecessor blocks. If they are instructions in SI's
+ // block, we can't map to the predecessor.
if (isa<PHINode>(SI.getCondition()) &&
- isa<Constant>(SI.getTrueValue()) &&
- isa<Constant>(SI.getFalseValue()))
+ (!isDefinedInBB(SI.getTrueValue(), SI.getParent()) ||
+ isa<PHINode>(SI.getTrueValue())) &&
+ (!isDefinedInBB(SI.getFalseValue(), SI.getParent()) ||
+ isa<PHINode>(SI.getFalseValue())))
if (Instruction *NV = FoldOpIntoPhi(SI))
return NV;