[unordered] sink unordered stores at end of blocks

The existing code turned out to be completely correct when auditted.  Thus, only minor code changes and adding a couple of tests.

llvm-svn: 267215

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index aa72244..e831400 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -1193,10 +1193,6 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
   if (isa<UndefValue>(Val))
     return eraseInstFromFunction(SI);
 
-  // The code below needs to be audited and adjusted for unordered atomics
-  if (!SI.isSimple())
-    return nullptr;
-
   // If this store is the last instruction in the basic block (possibly
   // excepting debug info instructions), and if the block ends with an
   // unconditional branch, try to move it to the successor block.
@@ -1222,6 +1218,9 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
 /// into a phi node with a store in the successor.
 ///
 bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) {
+  assert(SI.isUnordered() &&
+         "this code has not been auditted for volatile or ordered store case");
+  
   BasicBlock *StoreBB = SI.getParent();
 
   // Check to see if the successor block has exactly two incoming edges.  If

diff --git a/llvm/test/Transforms/InstCombine/atomic.ll b/llvm/test/Transforms/InstCombine/atomic.ll
index 408bc81..b1c4a29 100644 (file)
--- a/llvm/test/Transforms/InstCombine/atomic.ll
+++ b/llvm/test/Transforms/InstCombine/atomic.ll
@@ -211,3 +211,37 @@ define i32 @test21(i32** %p, i8* %v) {
   store atomic i32* %cast, i32** %p monotonic, align 4
   ret i32 0
 }
+
+define i32 @test22(i1 %cnd) {
+; CHECK-LABEL: define i32 @test22(
+; CHECK: [[PHI:%.*]] = phi i32
+; CHECK: store atomic i32 [[PHI]], i32* @a unordered, align 4
+  br i1 %cnd, label %block1, label %block2
+
+block1:
+  store atomic i32 1, i32* @a unordered, align 4
+  br label %merge
+block2:
+  store atomic i32 2, i32* @a unordered, align 4
+  br label %merge
+
+merge:
+  ret i32 0
+}
+
+; TODO: probably also legal here
+define i32 @test23(i1 %cnd) {
+; CHECK-LABEL: define i32 @test23(
+; CHECK: br i1 %cnd, label %block1, label %block2
+  br i1 %cnd, label %block1, label %block2
+
+block1:
+  store atomic i32 1, i32* @a monotonic, align 4
+  br label %merge
+block2:
+  store atomic i32 2, i32* @a monotonic, align 4
+  br label %merge
+
+merge:
+  ret i32 0
+}