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[InstCombine] Match scalable splats in m_ImmConstant #132522

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Merged
merged 6 commits into from
Apr 2, 2025
Merged

[InstCombine] Match scalable splats in m_ImmConstant #132522

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5cb140c
Precommit tests
lukel97 Mar 22, 2025
25172e1
[InstCombine] Allow folds of shifts by constants for scalable vectors…
lukel97 Mar 22, 2025
a0f4ac6
Rework to adjust m_ImmConstant
lukel97 Mar 24, 2025
e1b5509
Remove fixme
lukel97 Mar 24, 2025
0de7c62
Merge branch 'main' into instcombine/FoldShiftByConstant-scalable-splat
lukel97 Apr 2, 2025
ae87e3b
Update llvm/include/llvm/IR/PatternMatch.h
lukel97 Apr 2, 2025
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5 changes: 4 additions & 1 deletion llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
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Expand Up @@ -428,7 +428,10 @@ Instruction *InstCombinerImpl::commonShiftTransforms(BinaryOperator &I) {
return R;

Constant *CUI;
if (match(Op1, m_ImmConstant(CUI)))
if (match(Op1, m_Constant(CUI)) &&
(!isa<ConstantExpr>(CUI) ||
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@dtcxzyw dtcxzyw Mar 22, 2025

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Can you add a fixme here to note that we should remove this special case after we use ConstantInt to represent a scalable vector splat by default?

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@lukel97 lukel97 Mar 24, 2025

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Done in the matcher for a0f4ac6

(Ty->isVectorTy() &&
isa_and_present<ConstantInt>(CUI->getSplatValue()))))
if (Instruction *Res = FoldShiftByConstant(Op0, CUI, I))
return Res;

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11 changes: 11 additions & 0 deletions llvm/test/Transforms/InstCombine/shl-bo.ll
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Expand Up @@ -656,3 +656,14 @@ define <16 x i8> @test_FoldShiftByConstant_CreateAnd(<16 x i8> %in0) {
%vshl_n = shl <16 x i8> %tmp, <i8 5, i8 5, i8 5, i8 5, i8 5, i8 5, i8 5, i8 5, i8 5, i8 5, i8 5, i8 5, i8 5, i8 5, i8 5, i8 5>
ret <16 x i8> %vshl_n
}

define <vscale x 1 x i8> @test_FoldShiftByConstant_CreateAnd_scalable(<vscale x 1 x i8> %x) {
; CHECK-LABEL: @test_FoldShiftByConstant_CreateAnd_scalable(
; CHECK-NEXT: [[TMP1:%.*]] = shl <vscale x 1 x i8> [[X:%.*]], splat (i8 2)
; CHECK-NEXT: [[TMP2:%.*]] = and <vscale x 1 x i8> [[TMP1]], splat (i8 8)
; CHECK-NEXT: ret <vscale x 1 x i8> [[TMP2]]
;
%1 = and <vscale x 1 x i8> %x, splat (i8 2)
%2 = shl <vscale x 1 x i8> %1, splat (i8 2)
ret <vscale x 1 x i8> %2
}
11 changes: 11 additions & 0 deletions llvm/test/Transforms/InstCombine/shl-twice-constant.ll
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Expand Up @@ -14,3 +14,14 @@ define i64 @testfunc() {
%shl2 = shl i64 %shl1, ptrtoint (ptr @c to i64)
ret i64 %shl2
}

define <vscale x 1 x i64> @scalable() {
; CHECK-LABEL: @scalable(
; CHECK-NEXT: [[SHL1:%.*]] = shl nuw <vscale x 1 x i64> splat (i64 1), shufflevector (<vscale x 1 x i64> insertelement (<vscale x 1 x i64> poison, i64 ptrtoint (ptr @c2 to i64), i64 0), <vscale x 1 x i64> poison, <vscale x 1 x i32> zeroinitializer)
; CHECK-NEXT: [[SHL2:%.*]] = shl <vscale x 1 x i64> [[SHL1]], shufflevector (<vscale x 1 x i64> insertelement (<vscale x 1 x i64> poison, i64 ptrtoint (ptr @c to i64), i64 0), <vscale x 1 x i64> poison, <vscale x 1 x i32> zeroinitializer)
; CHECK-NEXT: ret <vscale x 1 x i64> [[SHL2]]
;
%shl1 = shl <vscale x 1 x i64> splat (i64 1), splat (i64 ptrtoint (ptr @c2 to i64))
%shl2 = shl <vscale x 1 x i64> %shl1, splat (i64 ptrtoint (ptr @c to i64))
ret <vscale x 1 x i64> %shl2
}