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[AArch64][GlobalISel] Don't crash when legalising vector G_SHL #168848

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Merged
cofibrant merged 4 commits into from
Dec 2, 2025
Merged

[AArch64][GlobalISel] Don't crash when legalising vector G_SHL #168848

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7683b54
[AArch64][GlobalISel] Don't crash when legalising vector G_SHL
cofibrant Nov 20, 2025
92db3f7
Modify handling of `G_*SH*` opcodes in `LegalizerHelper::moreElements…
cofibrant Dec 1, 2025
8e7ad65
Relocate test case
cofibrant Dec 1, 2025
0425039
Make sure the test case won't be optimised out
cofibrant Dec 1, 2025
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21 changes: 15 additions & 6 deletions llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6684,13 +6684,24 @@ LegalizerHelper::moreElementsVector(MachineInstr &MI, unsigned TypeIdx,
case TargetOpcode::G_FMAXIMUMNUM:
case TargetOpcode::G_STRICT_FADD:
case TargetOpcode::G_STRICT_FSUB:
case TargetOpcode::G_STRICT_FMUL:
case TargetOpcode::G_STRICT_FMUL: {
Observer.changingInstr(MI);
moreElementsVectorSrc(MI, MoreTy, 1);
moreElementsVectorSrc(MI, MoreTy, 2);
moreElementsVectorDst(MI, MoreTy, 0);
Observer.changedInstr(MI);
return Legalized;
}
case TargetOpcode::G_SHL:
case TargetOpcode::G_ASHR:
case TargetOpcode::G_LSHR: {
Observer.changingInstr(MI);
moreElementsVectorSrc(MI, MoreTy, 1);
moreElementsVectorSrc(MI, MoreTy, 2);
// The shift operand may have a different scalar type from the source and
// destination operands.
LLT ShiftMoreTy = MoreTy.changeElementType(
MRI.getType(MI.getOperand(2).getReg()).getElementType());
moreElementsVectorSrc(MI, ShiftMoreTy, 2);
moreElementsVectorDst(MI, MoreTy, 0);
Observer.changedInstr(MI);
return Legalized;
Expand Down Expand Up @@ -6806,12 +6817,10 @@ LegalizerHelper::moreElementsVector(MachineInstr &MI, unsigned TypeIdx,
LLT DstExtTy;
if (TypeIdx == 0) {
DstExtTy = MoreTy;
SrcExtTy = LLT::fixed_vector(
MoreTy.getNumElements(),
SrcExtTy = MoreTy.changeElementType(
MRI.getType(MI.getOperand(1).getReg()).getElementType());
} else {
DstExtTy = LLT::fixed_vector(
MoreTy.getNumElements(),
DstExtTy = MoreTy.changeElementType(
MRI.getType(MI.getOperand(0).getReg()).getElementType());
SrcExtTy = MoreTy;
}
Expand Down
28 changes: 28 additions & 0 deletions llvm/test/CodeGen/AArch64/shift.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -1033,6 +1033,34 @@ define <2 x i128> @lshr_v2i128(<2 x i128> %0, <2 x i128> %1){
ret <2 x i128> %3
}

define <2 x i8> @pr168848() {
; CHECK-SD-LABEL: pr168848:
; CHECK-SD: // %bb.0: // %entry
; CHECK-SD-NEXT: movi v0.2s, #1
; CHECK-SD-NEXT: ret
;
; CHECK-GI-LABEL: pr168848:
; CHECK-GI: // %bb.0: // %entry
; CHECK-GI-NEXT: mov w8, #1 // =0x1
; CHECK-GI-NEXT: mov w9, #0 // =0x0
; CHECK-GI-NEXT: fmov s0, w8
; CHECK-GI-NEXT: fmov s1, w9
; CHECK-GI-NEXT: mov v0.b[1], w8
; CHECK-GI-NEXT: mov v1.b[1], w9
; CHECK-GI-NEXT: ushl v0.8b, v0.8b, v1.8b
; CHECK-GI-NEXT: umov w8, v0.b[0]
; CHECK-GI-NEXT: umov w9, v0.b[1]
; CHECK-GI-NEXT: fmov s0, w8
; CHECK-GI-NEXT: mov v0.s[1], w9
; CHECK-GI-NEXT: // kill: def $d0 killed $d0 killed $q0
; CHECK-GI-NEXT: ret
entry:
%zeroes = zext <2 x i1> zeroinitializer to <2 x i32>
%ones = shl <2 x i32> splat (i32 1), %zeroes
%ones.trunc = trunc <2 x i32> %ones to <2 x i8>
ret <2 x i8> %ones.trunc
}

; ===== Vector with Non-Pow 2 Width =====

define <3 x i8> @shl_v3i8(<3 x i8> %0, <3 x i8> %1){
Expand Down