[llvm] d44cd1b - Revert "[FunctionAttrs] Make location classification more precise"

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2022-10-13T12:11:04+02:00
New Revision: d44cd1bbeb7542eba06401279e5f2c117247019b

URL: https://github.com/llvm/llvm-project/commit/d44cd1bbeb7542eba06401279e5f2c117247019b
DIFF: https://github.com/llvm/llvm-project/commit/d44cd1bbeb7542eba06401279e5f2c117247019b.diff

LOG: Revert "[FunctionAttrs] Make location classification more precise"

This reverts commit b05f5b90a12098660a4fc16da0b4d421ddfe14e2.

There are thread sanitizer buildbot failures in simple_stack.c.
I think that's because this ended up affecting the handling of
volatile accesses to allocas. Reverting for now.

Added: 
    

Modified: 
    llvm/lib/Transforms/IPO/FunctionAttrs.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
index a5bf7543472c..007d84a702fa 100644
--- a/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -139,19 +139,10 @@ checkFunctionMemoryAccess(Function &F, bool ThisBody, AAResults &AAR,
       F.getAttributes().hasAttrSomewhere(Attribute::Preallocated))
     MRB |= FunctionModRefBehavior::argMemOnly(ModRefInfo::ModRef);
 
-  auto AddPtrAccess = [&](const Value *Ptr, ModRefInfo MR) {
+  // Returns true if Ptr is not based on a function argument.
+  auto IsArgumentOrAlloca = [](const Value *Ptr) {
     const Value *UO = getUnderlyingObject(Ptr);
-    if (isa<AllocaInst>(UO))
-      return;
-    if (isa<Argument>(UO)) {
-      MRB |= FunctionModRefBehavior::argMemOnly(MR);
-      return;
-    }
-    // If it's not an identified object, it might be an argument.
-    if (!isIdentifiedObject(UO))
-      MRB |= FunctionModRefBehavior::argMemOnly(MR);
-    MRB |= FunctionModRefBehavior(FunctionModRefBehavior::Other, MR);
-    return;
+    return isa<Argument>(UO) || isa<AllocaInst>(UO);
   };
   // Scan the function body for instructions that may read or write memory.
   for (Instruction &I : instructions(F)) {
@@ -202,7 +193,9 @@ checkFunctionMemoryAccess(Function &F, bool ThisBody, AAResults &AAR,
           if (AAR.pointsToConstantMemory(Loc, /*OrLocal=*/true))
             continue;
 
-          AddPtrAccess(Loc.Ptr, ArgMR);
+          MRB |= FunctionModRefBehavior::argMemOnly(ArgMR);
+          if (!IsArgumentOrAlloca(Loc.Ptr))
+            MRB |= FunctionModRefBehavior(FunctionModRefBehavior::Other, ArgMR);
         }
       }
       continue;
@@ -228,7 +221,11 @@ checkFunctionMemoryAccess(Function &F, bool ThisBody, AAResults &AAR,
     if (!I.isVolatile() && AAR.pointsToConstantMemory(*Loc, /*OrLocal=*/true))
       continue;
 
-    AddPtrAccess(Loc->Ptr, MR);
+    // The accessed location can be either only argument memory, or
+    // argument & other memory, but never inaccessible memory.
+    MRB |= FunctionModRefBehavior::argMemOnly(MR);
+    if (!IsArgumentOrAlloca(Loc->Ptr))
+      MRB |= FunctionModRefBehavior(FunctionModRefBehavior::Other, MR);
   }
 
   return OrigMRB & MRB;