[clang] [llvm] [mlir] [IR][ModRef] Introduce `errno` memory location (PR #120783)

[Nikita Popov via cfe-commits]

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@@ -126,8 +126,21 @@ static void addLocAccess(MemoryEffects &ME, const MemoryLocation &Loc,
     return;
   if (isa<Argument>(UO)) {
     ME |= MemoryEffects::argMemOnly(MR);
+    if (Loc.Size <= LocationSize::precise(sizeof(int)))
+      ME |= MemoryEffects::errnoMemOnly(MR);
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nikic wrote:

This doesn't look right. Even if the argument might alias errno, it's still argmem from the perspective of this function. The caller has to deal with what the argument actually points to.

https://github.com/llvm/llvm-project/pull/120783