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Fix for PR18045: 

http://llvm.org/bugs/show_bug.cgi?id=18045

Short issue description:
For X86 machines with sse < sse4.1 we got failures for some
particular load/store vector sequences:

$ clang-trunk -m32 -O2 test-case.c
fatal error: error in backend: Cannot select: 0x4200920: v4i32,ch = load 0x41d6ab0, 0x4205850,
      0x41dcb10<LD16[getelementptr inbounds ([4 x i32]* @e, i32 0, i32 0)](align=4)> [ORD=82]
      [ID=58]
  0x4205850: i32 = X86ISD::Wrapper 0x41d5490 [ORD=26] [ID=43]
    0x41d5490: i32 = TargetGlobalAddress<[4 x i32]* @e> 0 [ORD=26] [ID=23]
  0x41dcb10: i32 = undef [ID=2]

The reason is that EltsFromConsecutiveLoads could emit such load instruction
both before and after legalize stage. Though this instruction is not legal for
machines with SSSE3 and lower.

The fix: In EltsFromConsecutiveLoads, if we have passed legalize stage, we
check whether nodes it emits are legal. 

P.S.: If you get failure in time from 12:00 and till 22:00 (UTC-8),
perhaps I'll slow with response, so you better reject this commit. Thanks!

llvm-svn: 197492
This commit is contained in:
Stepan Dyatkovskiy 2013-12-17 12:07:33 +00:00
parent 25d010a98d
commit 7f7c2710e0
2 changed files with 37 additions and 3 deletions
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13
llvm/lib/Target/X86/X86ISelLowering.cpp
View File

@ -5426,7 +5426,8 @@ LowerAsSplatVectorLoad(SDValue SrcOp, MVT VT, SDLoc dl, SelectionDAG &DAG) {
/// rather than undef via VZEXT_LOAD, but we do not detect that case today. /// rather than undef via VZEXT_LOAD, but we do not detect that case today.
/// There's even a handy isZeroNode for that purpose. /// There's even a handy isZeroNode for that purpose.
static SDValue EltsFromConsecutiveLoads(EVT VT, SmallVectorImpl<SDValue> &Elts, static SDValue EltsFromConsecutiveLoads(EVT VT, SmallVectorImpl<SDValue> &Elts,
SDLoc &DL, SelectionDAG &DAG) { SDLoc &DL, SelectionDAG &DAG,
bool isAfterLegalize) {
EVT EltVT = VT.getVectorElementType(); EVT EltVT = VT.getVectorElementType();
unsigned NumElems = Elts.size(); unsigned NumElems = Elts.size();
@ -5462,7 +5463,13 @@ static SDValue EltsFromConsecutiveLoads(EVT VT, SmallVectorImpl<SDValue> &Elts,
// load of the entire vector width starting at the base pointer. If we found // load of the entire vector width starting at the base pointer. If we found
// consecutive loads for the low half, generate a vzext_load node. // consecutive loads for the low half, generate a vzext_load node.
if (LastLoadedElt == NumElems - 1) { if (LastLoadedElt == NumElems - 1) {
if (isAfterLegalize &&
!DAG.getTargetLoweringInfo().isOperationLegal(ISD::LOAD, VT))
return SDValue();
SDValue NewLd = SDValue(); SDValue NewLd = SDValue();
if (DAG.InferPtrAlignment(LDBase->getBasePtr()) >= 16) if (DAG.InferPtrAlignment(LDBase->getBasePtr()) >= 16)
NewLd = DAG.getLoad(VT, DL, LDBase->getChain(), LDBase->getBasePtr(), NewLd = DAG.getLoad(VT, DL, LDBase->getChain(), LDBase->getBasePtr(),
LDBase->getPointerInfo(), LDBase->getPointerInfo(),
@ -6106,7 +6113,7 @@ X86TargetLowering::LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const {
V[i] = Op.getOperand(i); V[i] = Op.getOperand(i);
// Check for elements which are consecutive loads. // Check for elements which are consecutive loads.
SDValue LD = EltsFromConsecutiveLoads(VT, V, dl, DAG); SDValue LD = EltsFromConsecutiveLoads(VT, V, dl, DAG, false);
if (LD.getNode()) if (LD.getNode())
return LD; return LD;
@ -16379,7 +16386,7 @@ static SDValue PerformShuffleCombine(SDNode *N, SelectionDAG &DAG,
for (unsigned i = 0, e = VT.getVectorNumElements(); i != e; ++i) for (unsigned i = 0, e = VT.getVectorNumElements(); i != e; ++i)
Elts.push_back(getShuffleScalarElt(N, i, DAG, 0)); Elts.push_back(getShuffleScalarElt(N, i, DAG, 0));
return EltsFromConsecutiveLoads(VT, Elts, dl, DAG); return EltsFromConsecutiveLoads(VT, Elts, dl, DAG, true);
} }
/// PerformTruncateCombine - Converts truncate operation to /// PerformTruncateCombine - Converts truncate operation to

27
llvm/test/CodeGen/X86/v4i32load-crash.ll Normal file
View File

@ -0,0 +1,27 @@
; RUN: llc --mcpu=x86-64 --mattr=ssse3 < %s
;PR18045:
;Issue of selection for 'v4i32 load'.
;This instruction is not legal for X86 CPUs with sse < 'sse4.1'.
;This node was generated by X86ISelLowering.cpp, EltsFromConsecutiveLoads
;static function after legilize stage.
@e = external global [4 x i32], align 4
@f = external global [4 x i32], align 4
; Function Attrs: nounwind
define void @fn3(i32 %el) {
entry:
%0 = load i32* getelementptr inbounds ([4 x i32]* @e, i32 0, i32 0)
%1 = load i32* getelementptr inbounds ([4 x i32]* @e, i32 0, i32 1)
%2 = load i32* getelementptr inbounds ([4 x i32]* @e, i32 0, i32 2)
%3 = load i32* getelementptr inbounds ([4 x i32]* @e, i32 0, i32 3)
%4 = insertelement <4 x i32> undef, i32 %0, i32 0
%5 = insertelement <4 x i32> %4, i32 %1, i32 1
%6 = insertelement <4 x i32> %5, i32 %2, i32 2
%7 = insertelement <4 x i32> %6, i32 %3, i32 3
%8 = add <4 x i32> %6, %7
store <4 x i32> %8, <4 x i32>* bitcast ([4 x i32]* @f to <4 x i32>*)
ret void
}