[PATCH] D126270: [InstCombine] Preserve !nosanitize for newly created instructions.

[Mingjie Xu via Phabricator via llvm-commits]

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If the source instruction has !nosanitize metadata, all instructions created during combining should also have it.

The !nosanitize metadata indicates that LLVM should not insert any sanitizer instrumentation.

This https://github.com/google/sanitizers/issues/1508 false positive is caused:

1. InstCombine do not preserve !nosanitize for newly created instructions if source instruction has !nosanitize metadata and
2. ASan instruments for pointer comparison and subtraction instruction even if it has !nosanitize metadata

This patch and D126269 <https://reviews.llvm.org/D126269> together will fix the false positive.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D126270

Files:
  llvm/lib/Transforms/InstCombine/InstructionCombining.cpp


Index: llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -4192,7 +4192,8 @@
     // Now that we have an instruction, try combining it to simplify it.
     Builder.SetInsertPoint(I);
     Builder.CollectMetadataToCopy(
-        I, {LLVMContext::MD_dbg, LLVMContext::MD_annotation});
+        I, {LLVMContext::MD_dbg, LLVMContext::MD_annotation,
+            I->getModule()->getMDKindID("nosanitize")});
 
 #ifndef NDEBUG
     std::string OrigI;
@@ -4208,7 +4209,8 @@
                           << "    New = " << *Result << '\n');
 
         Result->copyMetadata(*I,
-                             {LLVMContext::MD_dbg, LLVMContext::MD_annotation});
+                             {LLVMContext::MD_dbg, LLVMContext::MD_annotation,
+                              I->getModule()->getMDKindID("nosanitize")});
         // Everything uses the new instruction now.
         I->replaceAllUsesWith(Result);
 


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