[llvm] r228760 - EarlyCSE: It isn't safe to CSE across synchronization boundaries

[David Majnemer]

Author: majnemer
Date: Tue Feb 10 17:09:43 2015
New Revision: 228760

URL: http://llvm.org/viewvc/llvm-project?rev=228760&view=rev
Log:
EarlyCSE: It isn't safe to CSE across synchronization boundaries

This fixes PR22514.

Modified:
    llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp
    llvm/trunk/test/Transforms/EarlyCSE/basic.ll

Modified: llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp?rev=228760&r1=228759&r2=228760&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/EarlyCSE.cpp Tue Feb 10 17:09:43 2015
@@ -527,6 +527,9 @@ bool EarlyCSE::processNode(DomTreeNode *
       // Ignore volatile loads.
       if (MemInst.isVolatile()) {
         LastStore = nullptr;
+        // Don't CSE across synchronization boundaries.
+        if (Inst->mayWriteToMemory())
+          ++CurrentGeneration;
         continue;
       }
 

Modified: llvm/trunk/test/Transforms/EarlyCSE/basic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/EarlyCSE/basic.ll?rev=228760&r1=228759&r2=228760&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/EarlyCSE/basic.ll (original)
+++ llvm/trunk/test/Transforms/EarlyCSE/basic.ll Tue Feb 10 17:09:43 2015
@@ -193,4 +193,10 @@ define void @test11(i32 *%P) {
   ; CHECK-NEXT: ret void
 }
 
-
+define i32 @test12(i1 %B, i32* %P1, i32* %P2) {
+  %load0 = load i32* %P1
+  %1 = load atomic i32* %P2 seq_cst, align 4
+  %load1 = load i32* %P1
+  %sel = select i1 %B, i32 %load0, i32 %load1
+  ret i32 %sel
+}