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[DAG] Fix wrong canonicalization performed on shuffle nodes. 

This fixes a regression introduced by r226816.
When replacing a splat shuffle node with a constant build_vector,
make sure that the new build_vector has a valid number of elements.

Thanks to Patrik Hagglund for reporting this problem and providing a
small reproducible.

llvm-svn: 227002
This commit is contained in:
Andrea Di Biagio 2015-01-24 11:54:29 +00:00
parent 9dea5cdb8e
commit 8381475a75
2 changed files with 24 additions and 7 deletions
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16
llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -1538,13 +1538,15 @@ SDValue SelectionDAG::getVectorShuffle(EVT VT, SDLoc dl, SDValue N1,
if (Splat && Splat.getOpcode() == ISD::UNDEF)
return getUNDEF(VT);
bool SameNumElts =
V.getValueType().getVectorNumElements() == VT.getVectorNumElements();
// We only have a splat which can skip shuffles if there is a splatted
// value and no undef lanes rearranged by the shuffle.
if (Splat && UndefElements.none()) {
// Splat of <x, x, ..., x>, return <x, x, ..., x>, provided that the
// number of elements match or the value splatted is a zero constant.
if (V.getValueType().getVectorNumElements() ==
VT.getVectorNumElements())
if (SameNumElts)
return N1;
if (auto *C = dyn_cast<ConstantSDNode>(Splat))
if (C->isNullValue())
@ -1553,15 +1555,15 @@ SDValue SelectionDAG::getVectorShuffle(EVT VT, SDLoc dl, SDValue N1,
// If the shuffle itself creates a constant splat, build the vector
// directly.
if (AllSame) {
if (AllSame && SameNumElts) {
const SDValue &Splatted = BV->getOperand(MaskVec[0]);
if (isa<ConstantSDNode>(Splatted) || isa<ConstantFPSDNode>(Splatted)) {
SmallVector<SDValue, 8> Ops;
for (unsigned i = 0; i != NElts; ++i) {
for (unsigned i = 0; i != NElts; ++i)
Ops.push_back(Splatted);
}
SDValue NewBV = getNode(ISD::BUILD_VECTOR, dl,
BV->getValueType(0), Ops);
SDValue NewBV =
getNode(ISD::BUILD_VECTOR, dl, BV->getValueType(0), Ops);
// We may have jumped through bitcasts, so the type of the
// BUILD_VECTOR may not match the type of the shuffle.

15
llvm/test/CodeGen/X86/selectiondag-crash.ll Normal file
View File

@ -0,0 +1,15 @@
; RUN: llc -mtriple=x86_64-unknown-unknown -mcpu=corei7 < %s
; Check that llc doesn't crash in the attempt to fold a shuffle with
; a splat mask into a constant build_vector.
define <8 x i8> @autogen_SD26299(i8) {
BB:
%Shuff = shufflevector <8 x i32> <i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1, i32 -1>, <8 x i32> zeroinitializer, <8 x i32> <i32 2, i32 undef, i32 6, i32 8, i32 undef, i32 12, i32 14, i32 0>
%Shuff14 = shufflevector <8 x i32> %Shuff, <8 x i32> %Shuff, <8 x i32> <i32 7, i32 9, i32 11, i32 undef, i32 undef, i32 1, i32 3, i32 5>
%Shuff35 = shufflevector <8 x i32> %Shuff14, <8 x i32> %Shuff, <8 x i32> <i32 undef, i32 1, i32 3, i32 5, i32 7, i32 9, i32 11, i32 13>
%I42 = insertelement <8 x i32> %Shuff35, i32 88608, i32 0
%Shuff48 = shufflevector <8 x i32> %Shuff35, <8 x i32> %I42, <8 x i32> <i32 4, i32 6, i32 8, i32 10, i32 12, i32 14, i32 0, i32 2>
%Tr59 = trunc <8 x i32> %Shuff48 to <8 x i8>
ret <8 x i8> %Tr59
}