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release/18.x: [InstCombine] Fix shift calculation in InstCombineCasts (#84027) #84080

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Merged
merged 1 commit into from
Mar 11, 2024
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release/18.x: [InstCombine] Fix shift calculation in InstCombineCasts (#84027) #84080

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4 changes: 2 additions & 2 deletions llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2156,14 +2156,14 @@ static bool collectInsertionElements(Value *V, unsigned Shift,
Type *ElementIntTy = IntegerType::get(C->getContext(), ElementSize);

for (unsigned i = 0; i != NumElts; ++i) {
unsigned ShiftI = Shift + i * ElementSize;
unsigned ShiftI = i * ElementSize;
Constant *Piece = ConstantFoldBinaryInstruction(
Instruction::LShr, C, ConstantInt::get(C->getType(), ShiftI));
if (!Piece)
return false;

Piece = ConstantExpr::getTrunc(Piece, ElementIntTy);
if (!collectInsertionElements(Piece, ShiftI, Elements, VecEltTy,
if (!collectInsertionElements(Piece, ShiftI + Shift, Elements, VecEltTy,
isBigEndian))
return false;
}
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15 changes: 15 additions & 0 deletions llvm/test/Transforms/InstCombine/bitcast.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -686,6 +686,21 @@ define ptr @bitcast_from_single_element_pointer_vector_to_pointer(<1 x ptr> %ptr
ret ptr %ptr
}

; Sure that we calculate the correct shift.
define <4 x i32> @bitcast_shl(i32 %arg) {
; CHECK-LABEL: @bitcast_shl(
; CHECK-NEXT: [[I5:%.*]] = insertelement <4 x i32> <i32 0, i32 0, i32 65, i32 poison>, i32 [[ARG:%.*]], i64 3
; CHECK-NEXT: ret <4 x i32> [[I5]]
;
%i = zext i32 %arg to i64
%i1 = shl i64 %i, 32
%i2 = or i64 %i1, 65
%i3 = zext i64 %i2 to i128
%i4 = shl i128 %i3, 64
%i5 = bitcast i128 %i4 to <4 x i32>
ret <4 x i32> %i5
}

declare void @f1()
declare void @f2()
define ptr @select_bitcast_unsized_pointer(i1 %c) {
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