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
diff --git a/lib/Analysis/IPA/GlobalsModRef.cpp b/lib/Analysis/IPA/GlobalsModRef.cpp
index 390a602..74327d5 100644
--- a/lib/Analysis/IPA/GlobalsModRef.cpp
+++ b/lib/Analysis/IPA/GlobalsModRef.cpp
@@ -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;
diff --git a/test/Analysis/GlobalsModRef/2008-09-13-VolatileRead.ll b/test/Analysis/GlobalsModRef/2008-09-13-VolatileRead.ll
new file mode 100644
index 0000000..8ac9637
--- /dev/null
+++ b/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
+}