[llvm-commits] [llvm] r41759 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/volatile_store.ll

[Chris Lattner]

Author: lattner
Date: Fri Sep  7 00:33:03 2007
New Revision: 41759

URL: http://llvm.org/viewvc/llvm-project?rev=41759&view=rev
Log:
Don't zap back to back volatile load/stores



Added:
    llvm/trunk/test/Transforms/InstCombine/volatile_store.ll
Modified:
    llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=41759&r1=41758&r2=41759&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Fri Sep  7 00:33:03 2007
@@ -9066,7 +9066,7 @@
     // the pointer we're loading and is producing the pointer we're storing,
     // then *this* store is dead (X = load P; store X -> P).
     if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) {
-      if (LI == Val && LI->getOperand(0) == Ptr) {
+      if (LI == Val && LI->getOperand(0) == Ptr && !SI.isVolatile()) {
         EraseInstFromFunction(SI);
         ++NumCombined;
         return 0;

Added: llvm/trunk/test/Transforms/InstCombine/volatile_store.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/volatile_store.ll?rev=41759&view=auto

==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/volatile_store.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/volatile_store.ll Fri Sep  7 00:33:03 2007
@@ -0,0 +1,14 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {volatile store}
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {volatile load}
+
+ at x = weak global i32 0		; <i32*> [#uses=2]
+
+define void @self_assign_1() {
+entry:
+	%tmp = volatile load i32* @x		; <i32> [#uses=1]
+	volatile store i32 %tmp, i32* @x
+	br label %return
+
+return:		; preds = %entry
+	ret void
+}