Fix PR2792: treat volatile loads as writing memory somewhere.

Treat stores as reading memory, just to play safe.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56188 91177308-0d34-0410-b5e6-96231b3b80d8

test/Analysis/GlobalsModRef/2008-09-13-VolatileRead.ll

@@ -0,0 +1,9 @@
+; RUN: llvm-as < %s | opt -globalsmodref-aa -markmodref | llvm-dis | not grep read
+; PR2792
+
+@g = global i32 0		; <i32*> [#uses=1]
+
+define i32 @f() {
+	%t = volatile load i32* @g		; <i32> [#uses=1]
+	ret i32 %t
+}