From 432d08cbdb9ceaa333f1d6eab4f8b542fdddf9db Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Wed, 10 Nov 2010 17:34:04 +0000
Subject: [PATCH] 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
---
 include/llvm/Analysis/AliasAnalysis.h | 13 ++++++++++---
 lib/Transforms/IPO/FunctionAttrs.cpp  |  5 ++---
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/llvm/Analysis/AliasAnalysis.h b/include/llvm/Analysis/AliasAnalysis.h
index 6b716ddee94..12b2090b174 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 3b1b13d378f..2e3440066e6 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.