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[DAGCombiner] Avoid introducing an illegal build_vector when folding a sign_extend. 

Make sure that we don't introduce illegal build_vector dag nodes
when trying to fold a sign_extend of a build_vector.

This fixes a regression introduced by r200234.
Added test CodeGen/X86/fold-vector-sext-crash.ll
to verify that llc no longer crashes with an assertion failure
due to an illegal build_vector of type MVT::v4i64.

Thanks to Ilia Filippov for spotting this regression and for
providing a reproducible test case.

llvm-svn: 200313
This commit is contained in:
Andrea Di Biagio 2014-01-28 12:53:56 +00:00
parent 77f5c20a5b
commit b6d39afbda
2 changed files with 27 additions and 9 deletions
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24
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -4583,7 +4583,8 @@ SDValue DAGCombiner::visitSETCC(SDNode *N) {
// dag nodes (see for example method DAGCombiner::visitSIGN_EXTEND).
// Vector extends are not folded if operations are legal; this is to
// avoid introducing illegal build_vector dag nodes.
static SDNode *tryToFoldExtendOfConstant(SDNode *N, SelectionDAG &DAG,
static SDNode *tryToFoldExtendOfConstant(SDNode *N, const TargetLowering &TLI,
SelectionDAG &DAG, bool LegalTypes,
bool LegalOperations) {
unsigned Opcode = N->getOpcode();
SDValue N0 = N->getOperand(0);
@ -4601,12 +4602,14 @@ static SDNode *tryToFoldExtendOfConstant(SDNode *N, SelectionDAG &DAG,
// fold (sext (build_vector AllConstants) -> (build_vector AllConstants)
// fold (zext (build_vector AllConstants) -> (build_vector AllConstants)
// fold (aext (build_vector AllConstants) -> (build_vector AllConstants)
if (!(VT.isVector() && !LegalOperations &&
EVT SVT = VT.getScalarType();
if (!(VT.isVector() &&
(!LegalTypes || (!LegalOperations && TLI.isTypeLegal(SVT))) &&
ISD::isBuildVectorOfConstantSDNodes(N0.getNode())))
return 0;
// We can fold this node into a build_vector.
unsigned VTBits = VT.getScalarType().getSizeInBits();
unsigned VTBits = SVT.getSizeInBits();
unsigned EVTBits = N0->getValueType(0).getScalarType().getSizeInBits();
unsigned ShAmt = VTBits - EVTBits;
SmallVector<SDValue, 8> Elts;
@ -4616,7 +4619,7 @@ static SDNode *tryToFoldExtendOfConstant(SDNode *N, SelectionDAG &DAG,
for (unsigned i=0; i != NumElts; ++i) {
SDValue Op = N0->getOperand(i);
if (Op->getOpcode() == ISD::UNDEF) {
Elts.push_back(DAG.getUNDEF(VT.getScalarType()));
Elts.push_back(DAG.getUNDEF(SVT));
continue;
}
@ -4624,10 +4627,10 @@ static SDNode *tryToFoldExtendOfConstant(SDNode *N, SelectionDAG &DAG,
const APInt &C = APInt(VTBits, CurrentND->getAPIntValue().getZExtValue());
if (Opcode == ISD::SIGN_EXTEND)
Elts.push_back(DAG.getConstant(C.shl(ShAmt).ashr(ShAmt).getZExtValue(),
VT.getScalarType()));
SVT));
else
Elts.push_back(DAG.getConstant(C.shl(ShAmt).lshr(ShAmt).getZExtValue(),
VT.getScalarType()));
SVT));
}
return DAG.getNode(ISD::BUILD_VECTOR, DL, VT, &Elts[0], NumElts).getNode();
@ -4723,7 +4726,8 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
SDValue N0 = N->getOperand(0);
EVT VT = N->getValueType(0);
if (SDNode *Res = tryToFoldExtendOfConstant(N, DAG, LegalOperations))
if (SDNode *Res = tryToFoldExtendOfConstant(N, TLI, DAG, LegalTypes,
LegalOperations))
return SDValue(Res, 0);
// fold (sext (sext x)) -> (sext x)
@ -4978,7 +4982,8 @@ SDValue DAGCombiner::visitZERO_EXTEND(SDNode *N) {
SDValue N0 = N->getOperand(0);
EVT VT = N->getValueType(0);
if (SDNode *Res = tryToFoldExtendOfConstant(N, DAG, LegalOperations))
if (SDNode *Res = tryToFoldExtendOfConstant(N, TLI, DAG, LegalTypes,
LegalOperations))
return SDValue(Res, 0);
// fold (zext (zext x)) -> (zext x)
@ -5247,7 +5252,8 @@ SDValue DAGCombiner::visitANY_EXTEND(SDNode *N) {
SDValue N0 = N->getOperand(0);
EVT VT = N->getValueType(0);
if (SDNode *Res = tryToFoldExtendOfConstant(N, DAG, LegalOperations))
if (SDNode *Res = tryToFoldExtendOfConstant(N, TLI, DAG, LegalTypes,
LegalOperations))
return SDValue(Res, 0);
// fold (aext (aext x)) -> (aext x)

12
llvm/test/CodeGen/X86/fold-vector-sext-crash.ll Normal file
View File

@ -0,0 +1,12 @@
; RUN: llc < %s -mcpu=core-avx-i -mtriple=i386-unknown-linux-gnu -mattr=+avx,+popcnt,+cmov
; Make sure that we don't introduce illegal build_vector dag nodes
; when trying to fold a sign_extend of a constant build_vector.
; After r200234 the test case below was crashing the compiler with an assertion failure
; due to an illegal build_vector of type MVT::v4i64.
define <4 x i64> @foo(<4 x i64> %A) {
%1 = select <4 x i1> <i1 true, i1 true, i1 false, i1 false>, <4 x i64> %A, <4 x i64><i64 undef, i64 undef, i64 0, i64 0>
ret <4 x i64> %1
}