[InstCombine] allow bitcast to/from FP for vector insert/extract transform
This is a follow-up to rL343482 / D52439.
This was a pattern that initially caused the commit to be reverted because
the transform requires a bitcast as shown here.
llvm-svn: 343794
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
index 945664d..f01f2b0 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -189,9 +189,7 @@
// If the source elements are wider than the destination, try to shift and
// truncate a subset of scalar bits of an insert op.
- // TODO: This is limited to integer types, but we could bitcast to/from FP.
- if (NumSrcElts < NumElts && SrcTy->getScalarType()->isIntegerTy() &&
- DestTy->getScalarType()->isIntegerTy()) {
+ if (NumSrcElts < NumElts) {
Value *Scalar;
uint64_t InsIndexC;
if (!match(X, m_InsertElement(m_Value(), m_Value(Scalar),
@@ -220,13 +218,42 @@
unsigned Chunk = ExtIndexC % NarrowingRatio;
if (IsBigEndian)
Chunk = NarrowingRatio - 1 - Chunk;
- unsigned ShAmt = Chunk * DestTy->getPrimitiveSizeInBits();
+
+ // Bail out if this is an FP vector to FP vector sequence. That would take
+ // more instructions than we started with unless there is no shift, and it
+ // may not be handled as well in the backend.
+ bool NeedSrcBitcast = SrcTy->getScalarType()->isFloatingPointTy();
+ bool NeedDestBitcast = DestTy->isFloatingPointTy();
+ if (NeedSrcBitcast && NeedDestBitcast)
+ return nullptr;
+
+ unsigned SrcWidth = SrcTy->getScalarSizeInBits();
+ unsigned DestWidth = DestTy->getPrimitiveSizeInBits();
+ unsigned ShAmt = Chunk * DestWidth;
+
+ // TODO: This limitation is more strict than necessary. We could sum the
+ // number of new instructions and subtract the number eliminated to know if
+ // we can proceed.
+ if (!X->hasOneUse() || !Ext.getVectorOperand()->hasOneUse())
+ if (NeedSrcBitcast || NeedDestBitcast)
+ return nullptr;
+
+ if (NeedSrcBitcast) {
+ Type *SrcIntTy = IntegerType::getIntNTy(Scalar->getContext(), SrcWidth);
+ Scalar = Builder.CreateBitCast(Scalar, SrcIntTy);
+ }
+
if (ShAmt) {
// Bail out if we could end with more instructions than we started with.
if (!Ext.getVectorOperand()->hasOneUse())
return nullptr;
Scalar = Builder.CreateLShr(Scalar, ShAmt);
}
+
+ if (NeedDestBitcast) {
+ Type *DestIntTy = IntegerType::getIntNTy(Scalar->getContext(), DestWidth);
+ return new BitCastInst(Builder.CreateTrunc(Scalar, DestIntTy), DestTy);
+ }
return new TruncInst(Scalar, DestTy);
}