🍒 [llvm] ASan Memory Effects #10268
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🍒 [llvm] ASan Memory Effects #10268
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If left as-is, subsequent optimizations might utilize the possible memory effects and optimize-out the instrumentation. Think of the following case: ``` store i8 4, ptr %shadow call void @llvm.lifetime.start.p0(i64 4, ptr %local) %28 = call void @foo(ptr %local) store i8 -8, ptr %shadow call void @llvm.lifetime.end.p0(i64 4, ptr %local) ``` where `foo` is an external function with `memory(argmem: write)`. A pass such as DeadStoreElimination is allowed to remove the initial store, which might fail sanitizer checks within `foo`. My first attempt was to add a `memory(readwrite)` at the call-site level, but unfortunately the current implementation of `getMemoryEffects` doesn't exactly give it "precedence" as specified, but rather restricts the access specified by the call-site and not the other way around as well.
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This was referenced Mar 23, 2025
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Fixes an issue when passes such as DeadStoreElimination follow AddressSanitizer instrumentation and may create false-positives.