Factor out the code for testing whether a function accesses

arbitrary memory into a helper function, and adjust some comments.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118687 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 12 insertions, 6 deletions

diff --git a/include/llvm/Analysis/AliasAnalysis.h b/include/llvm/Analysis/AliasAnalysis.h
index 6b716dd..12b2090 100644
--- a/include/llvm/Analysis/AliasAnalysis.h
+++ b/include/llvm/Analysis/AliasAnalysis.h
@@ -268,14 +268,21 @@ public:
     return onlyReadsMemory(getModRefBehavior(F));
   }
 
-  /// onlyReadsMemory - If the functions with the specified behavior are known
-  /// to only read from non-volatile memory (or not access memory at all), return
-  /// true.  For use when the call site is not known.
+  /// onlyReadsMemory - Return true if functions with the specified behavior are
+  /// known to only read from non-volatile memory (or not access memory at all).
   ///
   static bool onlyReadsMemory(ModRefBehavior MRB) {
     return !(MRB & Mod);
   }
 
+  /// onlyAccessesArgPointees - Return true if functions with the specified
+  /// behavior are known to read at most from objects pointed to by their
+  /// pointer-typed arguments (with arbitrary offsets).
+  ///
+  static bool onlyAccessesArgPointees(ModRefBehavior MRB) {
+    return !(MRB & Anywhere & ~ArgumentPointees);
+  }
+
   /// getModRefInfo - Return information about whether or not an instruction may
   /// read or write the specified memory location.  An instruction
   /// that doesn't read or write memory may be trivially LICM'd for example.
diff --git a/lib/Transforms/IPO/FunctionAttrs.cpp b/lib/Transforms/IPO/FunctionAttrs.cpp
index 3b1b13d..2e34400 100644
--- a/lib/Transforms/IPO/FunctionAttrs.cpp
+++ b/lib/Transforms/IPO/FunctionAttrs.cpp
@@ -131,9 +131,8 @@ bool FunctionAttrs::AddReadAttrs(const CallGraphSCC &SCC) {
         AliasAnalysis::ModRefBehavior MRB = AA->getModRefBehavior(CS);
         // If the call doesn't access arbitrary memory, we may be able to
         // figure out something.
-        if (!(MRB & AliasAnalysis::Anywhere &
-              ~AliasAnalysis::ArgumentPointees)) {
-          // If the call accesses argument pointees, check each argument.
+        if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
+          // If the call does access argument pointees, check each argument.
           if (MRB & AliasAnalysis::AccessesArguments)
             // Check whether all pointer arguments point to local memory, and
             // ignore calls that only access local memory.