[llvm-commits] [llvm] r50370 - in /llvm/trunk: lib/Transforms/Scalar/DeadStoreElimination.cpp test/Transforms/DeadStoreElimination/volatile-load.ll

[Dan Gohman]

Author: djg
Date: Mon Apr 28 14:51:27 2008
New Revision: 50370

URL: http://llvm.org/viewvc/llvm-project?rev=50370&view=rev
Log:
Fix DSE to not eliminate volatile loads with no uses.

Added:
    llvm/trunk/test/Transforms/DeadStoreElimination/volatile-load.ll
Modified:
    llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp?rev=50370&r1=50369&r2=50370&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp Mon Apr 28 14:51:27 2008
@@ -326,9 +326,9 @@
     
     // If we encounter a use of the pointer, it is no longer considered dead
     if (LoadInst* L = dyn_cast<LoadInst>(BBI)) {
-      // However, if this load is unused, we can go ahead and remove it, and
-      // not have to worry about it making our pointer undead!
-      if (L->use_empty()) {
+      // However, if this load is unused and not volatile, we can go ahead and remove it,
+      // and not have to worry about it making our pointer undead!
+      if (L->use_empty() && !L->isVolatile()) {
         MD.removeInstruction(L);
         
         // DCE instructions only used to calculate that load

Added: llvm/trunk/test/Transforms/DeadStoreElimination/volatile-load.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/DeadStoreElimination/volatile-load.ll?rev=50370&view=auto

==============================================================================
--- llvm/trunk/test/Transforms/DeadStoreElimination/volatile-load.ll (added)
+++ llvm/trunk/test/Transforms/DeadStoreElimination/volatile-load.ll Mon Apr 28 14:51:27 2008
@@ -0,0 +1,8 @@
+; RUN: llvm-as < %s | opt -dse | llvm-dis | grep {volatile load}
+
+ at g_1 = global i32 0
+
+define void @foo() nounwind  {
+	%t = volatile load i32* @g_1
+	ret void
+}