Changes in directory llvm/lib/Transforms/Scalar:
InstructionCombining.cpp updated: 1.455 -> 1.456
---
Log message:
If we can look through vector operations to find the scalar version of an
extract_element'd value, do so.
---
Diffs of the changes: (+40 -0)
InstructionCombining.cpp | 40 ++++++++++++++++++++++++++++++++++++++++
1 files changed, 40 insertions(+)
Index: llvm/lib/Transforms/Scalar/InstructionCombining.cpp
diff -u llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.455
llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.456
--- llvm/lib/Transforms/Scalar/InstructionCombining.cpp:1.455 Fri Mar 31
12:25:14 2006
+++ llvm/lib/Transforms/Scalar/InstructionCombining.cpp Fri Mar 31 17:01:56 2006
@@ -6654,7 +6654,41 @@
return false;
}
+/// FindScalarElement - Given a vector and an element number, see if the scalar
+/// value is already around as a register, for example if it were inserted then
+/// extracted from the vector.
+static Value *FindScalarElement(Value *V, unsigned EltNo) {
+ assert(isa<PackedType>(V->getType()) && "Not looking at a vector?");
+ const PackedType *PTy = cast<PackedType>(V->getType());
+ if (EltNo >= PTy->getNumElements()) // Out of range access.
+ return UndefValue::get(PTy->getElementType());
+
+ if (isa<UndefValue>(V))
+ return UndefValue::get(PTy->getElementType());
+ else if (isa<ConstantAggregateZero>(V))
+ return Constant::getNullValue(PTy->getElementType());
+ else if (ConstantPacked *CP = dyn_cast<ConstantPacked>(V))
+ return CP->getOperand(EltNo);
+ else if (InsertElementInst *III = dyn_cast<InsertElementInst>(V)) {
+ // If this is an insert to a variable element, we don't know what it is.
+ if (!isa<ConstantUInt>(III->getOperand(2))) return 0;
+ unsigned IIElt = cast<ConstantUInt>(III->getOperand(2))->getValue();
+
+ // If this is an insert to the element we are looking for, return the
+ // inserted value.
+ if (EltNo == IIElt) return III->getOperand(1);
+
+ // Otherwise, the insertelement doesn't modify the value, recurse on its
+ // vector input.
+ return FindScalarElement(III->getOperand(0), EltNo);
+ }
+
+ // Otherwise, we don't know.
+ return 0;
+}
+
Instruction *InstCombiner::visitExtractElementInst(ExtractElementInst &EI) {
+
// If packed val is undef, replace extract with scalar undef.
if (isa<UndefValue>(EI.getOperand(0)))
return ReplaceInstUsesWith(EI, UndefValue::get(EI.getType()));
@@ -6676,6 +6710,12 @@
return ReplaceInstUsesWith(EI, op0);
}
+ // If extracting a specified index from the vector, see if we can recursively
+ // find a previously computed scalar that was inserted into the vector.
+ if (ConstantUInt *IdxC = dyn_cast<ConstantUInt>(EI.getOperand(1)))
+ if (Value *Elt = FindScalarElement(EI.getOperand(0), IdxC->getValue()))
+ return ReplaceInstUsesWith(EI, Elt);
+
if (Instruction *I = dyn_cast<Instruction>(EI.getOperand(0)))
if (I->hasOneUse()) {
// Push extractelement into predecessor operation if legal and
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