[llvm] [RFC] Memory Model Relaxation Annotations (PR #78569)
Nikita Popov via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 7 23:48:10 PST 2024
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@@ -698,6 +700,16 @@ bool Instruction::hasSameSpecialState(const Instruction *I2,
assert(I1->getOpcode() == I2->getOpcode() &&
"Can not compare special state of different instructions");
+ // MMRAs may change semantics of an operation, e.g. make a fence only
+ // affect a given address space.
+ //
+ // FIXME: Not sure if this stinks or not. Maybe we should just look at
+ // all callers and make them check MMRAs.
+ // OTOH, MMRAs can really alter semantics so this is technically correct
+ // (the best kind of correct).
+ if (MMRAMetadata(*this) != MMRAMetadata(*I2))
----------------
nikic wrote:
I think if you want to aggressively not merge MMRAs, then you shouldn't be modelling them using metadata.
https://github.com/llvm/llvm-project/pull/78569
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