Since onlyReadsMemory returns true if in fact

doesNotAccessMemory, check doesNotAccessMemory
first, since otherwise functions may be
marked readonly rather than readnone.

llvm-svn: 55697

2 files changed, 13 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/IPA/GlobalsModRef.cpp b/llvm/lib/Analysis/IPA/GlobalsModRef.cpp
index c8347c23fdb..5f384694984 100644
--- a/llvm/lib/Analysis/IPA/GlobalsModRef.cpp
+++ b/llvm/lib/Analysis/IPA/GlobalsModRef.cpp
@@ -376,14 +376,16 @@ void GlobalsModRef::AnalyzeCallGraph(CallGraph &CG, Module &M) {
 
       if (F->isDeclaration()) {
         // Try to get mod/ref behaviour from function attributes.
-        if (F->onlyReadsMemory()) {
+        if (F->doesNotAccessMemory()) {
+          // Can't do better than that!
+        } else if (F->onlyReadsMemory()) {
           FunctionEffect |= Ref;
           // This function might call back into the module and read a global, so
           // mark all globals read somewhere as being read by this function.
           for (std::set<GlobalValue*>::iterator GI = ReadGlobals.begin(),
                E = ReadGlobals.end(); GI != E; ++GI)
             FR.GlobalInfo[*GI] |= Ref;
-        } else if (!F->doesNotAccessMemory()) {
+        } else {
           // Can't say anything useful.
           KnowNothing = true;
         }
diff --git a/llvm/test/Analysis/GlobalsModRef/2008-09-03-ReadNone.ll b/llvm/test/Analysis/GlobalsModRef/2008-09-03-ReadNone.ll
new file mode 100644
index 00000000000..b286ada8390
--- /dev/null
+++ b/llvm/test/Analysis/GlobalsModRef/2008-09-03-ReadNone.ll
@@ -0,0 +1,9 @@
+; RUN: llvm-as < %s | opt -globalsmodref-aa -markmodref | llvm-dis | grep readnone | count 2
+
+define i32 @f() {
+entry:
+	%tmp = call i32 @e( )		; <i32> [#uses=1]
+	ret i32 %tmp
+}
+
+declare i32 @e() readnone