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[LLVM][SimplifyCFG] Make validLookupTableConstant explicitly reject vector types. (#182555)

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validLookupTableConstant indirectly rejects vectors through its
selection of supported Constant classes. However, this is not sufficient
when ContantInt/FP are used to represent constant vector splats and so
I've added an explicit bailout.
This commit is contained in:
Paul Walker 2026-02-24 16:47:06 +00:00 committed by GitHub
parent 1a81673922
commit e8d8f8cfcc
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2 changed files with 50 additions and 0 deletions
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3
llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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@ -6324,6 +6324,9 @@ static bool validLookupTableConstant(Constant *C, const TargetTransformInfo &TTI
!isa<UndefValue>(C) && !isa<ConstantExpr>(C))
return false;
if (C->getType()->isVectorTy())
return false;
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
// Pointer casts and in-bounds GEPs will not prohibit the backend from
// materializing the array of constants.

47
llvm/test/Transforms/SimplifyCFG/AArch64/switch-to-lookup-table-vector-splat.ll Normal file
View File

@ -0,0 +1,47 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
; RUN: opt -passes='simplifycfg<switch-to-lookup>' -S < %s | FileCheck %s
; RUN: opt -passes='simplifycfg<switch-to-lookup>' -use-constant-fp-for-fixed-length-splat -S < %s | FileCheck %s
target triple = "aarch64-unknown-linux-gnu"
define <4 x float> @no_switch_to_lookup_table_vector_splat(i32 %c) {
; CHECK-LABEL: define <4 x float> @no_switch_to_lookup_table_vector_splat(
; CHECK-SAME: i32 [[C:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*]]:
; CHECK-NEXT: switch i32 [[C]], label %[[DEFAULT:.*]] [
; CHECK-NEXT: i32 0, label %[[RET:.*]]
; CHECK-NEXT: i32 1, label %[[BB1:.*]]
; CHECK-NEXT: i32 2, label %[[BB2:.*]]
; CHECK-NEXT: ]
; CHECK: [[BB1]]:
; CHECK-NEXT: br label %[[RET]]
; CHECK: [[BB2]]:
; CHECK-NEXT: br label %[[RET]]
; CHECK: [[DEFAULT]]:
; CHECK-NEXT: unreachable
; CHECK: [[RET]]:
; CHECK-NEXT: [[PHI:%.*]] = phi <4 x float> [ splat (float 3.000000e+00), %[[BB2]] ], [ splat (float 2.000000e+00), %[[BB1]] ], [ splat (float 1.000000e+00), %[[ENTRY]] ]
; CHECK-NEXT: ret <4 x float> [[PHI]]
entry:
switch i32 %c, label %default [
i32 0, label %bb0
i32 1, label %bb1
i32 2, label %bb2
]
bb0:
br label %ret
bb1:
br label %ret
bb2:
br label %ret
default:
unreachable
ret:
%phi = phi <4 x float> [ splat (float 1.0), %bb0 ], [ splat (float 2.0), %bb1 ], [ splat (float 3.0), %bb2 ]
ret <4 x float> %phi
}