[PATCH] D102348: [Instructions]: Calls marked with inaccessiblememonly attribute should be considered to not read/write memory

[Ettore Tiotto via Phabricator via llvm-commits]

etiotto created this revision.
etiotto added reviewers: Meinersbur, bmahjour, Whitney.
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The documentations states that functions with the `inaccessiblememonly` only access memory that is not accessible by the module bering compiled:

  inaccessiblememonly
  This attribute indicates that the function may only access memory that is not accessible by the module being compiled. This is a weaker form of readnone. If the function reads or writes other memory, the behavior is undefined.

Therefore the `Instruction::mayReadFromMemory()` and `Instruction::mayWriteToMemory()` should report that such functions do not read not write memory in the module being compiled.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D102348

Files:
  llvm/lib/IR/Instruction.cpp


Index: llvm/lib/IR/Instruction.cpp
===================================================================
--- llvm/lib/IR/Instruction.cpp
+++ llvm/lib/IR/Instruction.cpp
@@ -553,8 +553,10 @@
     return true;
   case Instruction::Call:
   case Instruction::Invoke:
-  case Instruction::CallBr:
-    return !cast<CallBase>(this)->doesNotReadMemory();
+  case Instruction::CallBr: {
+    const CallBase &CB = *cast<CallBase>(this);
+    return !CB.doesNotReadMemory() && !CB.onlyAccessesInaccessibleMemory();
+  }
   case Instruction::Store:
     return !cast<StoreInst>(this)->isUnordered();
   }
@@ -573,8 +575,10 @@
     return true;
   case Instruction::Call:
   case Instruction::Invoke:
-  case Instruction::CallBr:
-    return !cast<CallBase>(this)->onlyReadsMemory();
+  case Instruction::CallBr: {
+    const CallBase &CB = *cast<CallBase>(this);
+    return !CB.onlyReadsMemory() && !CB.onlyAccessesInaccessibleMemory();
+  }
   case Instruction::Load:
     return !cast<LoadInst>(this)->isUnordered();
   }


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