Don't let globalopt hack on volatile loads or stores.

llvm-svn: 46523

2 files changed, 13 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index ea8080e35e8..7bed9e22d11 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -163,12 +163,15 @@ static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
         else if (GS.AccessingFunction != F)
           GS.HasMultipleAccessingFunctions = true;
       }
-      if (isa<LoadInst>(I)) {
+      if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
         GS.isLoaded = true;
+        if (LI->isVolatile()) return true;  // Don't hack on volatile loads.
       } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
         // Don't allow a store OF the address, only stores TO the address.
         if (SI->getOperand(0) == V) return true;
 
+        if (SI->isVolatile()) return true;  // Don't hack on volatile stores.
+
         // If this is a direct store to the global (i.e., the global is a scalar
         // value, not an aggregate), keep more specific information about
         // stores.
diff --git a/llvm/test/Transforms/GlobalOpt/2008-01-29-VolatileGlobal.ll b/llvm/test/Transforms/GlobalOpt/2008-01-29-VolatileGlobal.ll
new file mode 100644
index 00000000000..0a8dd499c65
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/2008-01-29-VolatileGlobal.ll
@@ -0,0 +1,9 @@
+; RUN: llvm-as < %s | opt -globalopt | llvm-dis | grep {volatile load}
+@t0.1441 = internal global double 0x3FD5555555555555, align 8		; <double*> [#uses=1]
+
+define double @foo() nounwind  {
+entry:
+	%tmp1 = volatile load double* @t0.1441, align 8		; <double> [#uses=2]
+	%tmp4 = mul double %tmp1, %tmp1		; <double> [#uses=1]
+	ret double %tmp4
+}