[InstCombine] Fix shift calculation in InstCombineCasts

[dianqk]

Fixes #84025.

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Quentin Dian (DianQK)

Changes

Fixes #84025.

---

Full diff: https://github.com/llvm/llvm-project/pull/84027.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp (+2-2)
• (modified) llvm/test/Transforms/InstCombine/bitcast.ll (+15)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp index 33ed1d5575375a..45afa6363ae01f 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp @@ -2167,14 +2167,14 @@ 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; } diff --git a/llvm/test/Transforms/InstCombine/bitcast.ll b/llvm/test/Transforms/InstCombine/bitcast.ll index 176b432ea0b5c9..5599604b666fb7 100644 --- a/llvm/test/Transforms/InstCombine/bitcast.ll +++ b/llvm/test/Transforms/InstCombine/bitcast.ll @@ -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) { 

[nikic]

LGTM