If a function only reads memory, then we know that...

it only reads memory!  The other change has no
functional effect, it just seems more logical to
go in order of decreasing knowledge.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64463 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/AliasAnalysis.cpp b/lib/Analysis/AliasAnalysis.cpp
index 369f2f4f90e1e3f30f8d9c22ce11a60ced048068..67b2faac55dc49121c19fc63917a817fc1036fe3 100644 (file)
--- a/lib/Analysis/AliasAnalysis.cpp
+++ b/lib/Analysis/AliasAnalysis.cpp
@@ -120,9 +120,13 @@ AliasAnalysis::getModRefBehavior(CallSite CS,
 AliasAnalysis::ModRefBehavior
 AliasAnalysis::getModRefBehavior(Function *F,
                                  std::vector<PointerAccessInfo> *Info) {
-  if (F && F->doesNotAccessMemory())
-    // Can't do better than this.
-    return DoesNotAccessMemory;
+  if (F) {
+    if (F->doesNotAccessMemory())
+      // Can't do better than this.
+      return DoesNotAccessMemory;
+    else if (F->onlyReadsMemory())
+      return OnlyReadsMemory;
+  }
   return UnknownModRefBehavior;
 }
 
@@ -130,10 +134,10 @@ AliasAnalysis::ModRefResult
 AliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
   ModRefResult Mask = ModRef;
   ModRefBehavior MRB = getModRefBehavior(CS);
-  if (MRB == OnlyReadsMemory)
-    Mask = Ref;
-  else if (MRB == DoesNotAccessMemory)
+  if (MRB == DoesNotAccessMemory)
     return NoModRef;
+  else if (MRB == OnlyReadsMemory)
+    Mask = Ref;
   else if (MRB == AliasAnalysis::AccessesArguments) {
     bool doesAlias = false;
     for (CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
@@ -142,7 +146,7 @@ AliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
         doesAlias = true;
         break;
       }
-    
+
     if (!doesAlias)
       return NoModRef;
   }