[llvm-commits] [llvm] r56188 - in /llvm/trunk: lib/Analysis/IPA/GlobalsModRef.cpp test/Analysis/GlobalsModRef/2008-09-13-VolatileRead.ll

[Duncan Sands]

Author: baldrick
Date: Sat Sep 13 07:45:50 2008
New Revision: 56188

URL: http://llvm.org/viewvc/llvm-project?rev=56188&view=rev
Log:
Fix PR2792: treat volatile loads as writing memory somewhere.
Treat stores as reading memory, just to play safe.

Added:
    llvm/trunk/test/Analysis/GlobalsModRef/2008-09-13-VolatileRead.ll
Modified:
    llvm/trunk/lib/Analysis/IPA/GlobalsModRef.cpp

Modified: llvm/trunk/lib/Analysis/IPA/GlobalsModRef.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/IPA/GlobalsModRef.cpp?rev=56188&r1=56187&r2=56188&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/IPA/GlobalsModRef.cpp (original)
+++ llvm/trunk/lib/Analysis/IPA/GlobalsModRef.cpp Sat Sep 13 07:45:50 2008
@@ -431,12 +431,20 @@
       for (inst_iterator II = inst_begin(SCC[i]->getFunction()),
              E = inst_end(SCC[i]->getFunction());
            II != E && FunctionEffect != ModRef; ++II)
-        if (isa<LoadInst>(*II))
+        if (isa<LoadInst>(*II)) {
           FunctionEffect |= Ref;
-        else if (isa<StoreInst>(*II))
+          if (cast<LoadInst>(*II).isVolatile())
+            // Volatile loads may have side-effects, so mark them as writing
+            // memory (for example, a flag inside the processor).
+            FunctionEffect |= Mod;
+        } else if (isa<StoreInst>(*II)) {
           FunctionEffect |= Mod;
-        else if (isa<MallocInst>(*II) || isa<FreeInst>(*II))
+          if (cast<StoreInst>(*II).isVolatile())
+            // Treat volatile stores as reading memory somewhere.
+            FunctionEffect |= Ref;
+        } else if (isa<MallocInst>(*II) || isa<FreeInst>(*II)) {
           FunctionEffect |= ModRef;
+        }
 
     if ((FunctionEffect & Mod) == 0)
       ++NumReadMemFunctions;

Added: llvm/trunk/test/Analysis/GlobalsModRef/2008-09-13-VolatileRead.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Analysis/GlobalsModRef/2008-09-13-VolatileRead.ll?rev=56188&view=auto

==============================================================================
--- llvm/trunk/test/Analysis/GlobalsModRef/2008-09-13-VolatileRead.ll (added)
+++ llvm/trunk/test/Analysis/GlobalsModRef/2008-09-13-VolatileRead.ll Sat Sep 13 07:45:50 2008
@@ -0,0 +1,9 @@
+; RUN: llvm-as < %s | opt -globalsmodref-aa -markmodref | llvm-dis | not grep read
+; PR2792
+
+ at g = global i32 0		; <i32*> [#uses=1]
+
+define i32 @f() {
+	%t = volatile load i32* @g		; <i32> [#uses=1]
+	ret i32 %t
+}