[llvm] [asan][x86] Abort instrumenting memintrinsics that target fs, gs (PR #129291)

[Alexander Potapenko via llvm-commits]

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@@ -1340,10 +1341,21 @@ Value *AddressSanitizer::memToShadow(Value *Shadow, IRBuilder<> &IRB) {
     return IRB.CreateAdd(Shadow, ShadowBase);
 }
 
+bool AddressSanitizer::maybeIgnoreMemIntrinsic(MemIntrinsic *MI,
+                                               const Triple &TargetTriple) {
+  // Ignore FS and GS registers to prevent miscompilation
+  if (MI->getDestAddressSpace() >= 256 &&
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ramosian-glider wrote:

Do we also want to bail out if the address space is 258 (SS), 259 etc.?

https://github.com/llvm/llvm-project/pull/129291