f58930f705
If there is a single store, then loads must either load the stored value or uninitialized memory (undef). If the stored value may be poison, then replacing an uninitialized memory load with it would be incorrect. Fall back to the generic code in that case. This PR only fixes the case where there is a literal poison store -- the case where the value is non-trivially poison will still get miscompiled by phi simplification later, see #96631. Fixes https://github.com/llvm/llvm-project/issues/97702.
67 lines
1.7 KiB
LLVM
67 lines
1.7 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
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; RUN: opt -S -passes=mem2reg < %s | FileCheck %s
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define i8 @single_store_literal_poison(i1 %cond) {
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; CHECK-LABEL: define i8 @single_store_literal_poison(
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; CHECK-SAME: i1 [[COND:%.*]]) {
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; CHECK-NEXT: br i1 [[COND]], label %[[IF:.*]], label %[[EXIT:.*]]
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; CHECK: [[IF]]:
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; CHECK-NEXT: br label %[[EXIT]]
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; CHECK: [[EXIT]]:
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; CHECK-NEXT: ret i8 undef
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;
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%a = alloca i8, align 1
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br i1 %cond, label %if, label %exit
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if:
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store i8 poison, ptr %a, align 1
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br label %exit
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exit:
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%v = load i8, ptr %a, align 1
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ret i8 %v
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}
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; FIXME: This is a miscompile.
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define i8 @single_store_maybe_poison(i1 %cond, i8 %x) {
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; CHECK-LABEL: define i8 @single_store_maybe_poison(
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; CHECK-SAME: i1 [[COND:%.*]], i8 [[X:%.*]]) {
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; CHECK-NEXT: br i1 [[COND]], label %[[IF:.*]], label %[[EXIT:.*]]
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; CHECK: [[IF]]:
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; CHECK-NEXT: br label %[[EXIT]]
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; CHECK: [[EXIT]]:
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; CHECK-NEXT: ret i8 [[X]]
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;
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%a = alloca i8, align 1
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br i1 %cond, label %if, label %exit
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if:
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store i8 %x, ptr %a, align 1
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br label %exit
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exit:
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%v = load i8, ptr %a, align 1
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ret i8 %v
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}
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define i8 @single_store_cant_be_poison(i1 %cond, i8 noundef %x) {
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; CHECK-LABEL: define i8 @single_store_cant_be_poison(
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; CHECK-SAME: i1 [[COND:%.*]], i8 noundef [[X:%.*]]) {
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; CHECK-NEXT: br i1 [[COND]], label %[[IF:.*]], label %[[EXIT:.*]]
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; CHECK: [[IF]]:
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; CHECK-NEXT: br label %[[EXIT]]
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; CHECK: [[EXIT]]:
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; CHECK-NEXT: ret i8 [[X]]
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;
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%a = alloca i8, align 1
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br i1 %cond, label %if, label %exit
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if:
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store i8 %x, ptr %a, align 1
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br label %exit
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exit:
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%v = load i8, ptr %a, align 1
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ret i8 %v
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}
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