[Instcombine] Combine consecutive identical fences

Differential Revision:  https://reviews.llvm.org/D29314

llvm-svn: 293661

1 files changed, 47 insertions, 0 deletions

diff --git a/llvm/test/Transforms/InstCombine/consecutive-fences.ll b/llvm/test/Transforms/InstCombine/consecutive-fences.ll
new file mode 100644
index 00000000000..6f1c4127738
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/consecutive-fences.ll
@@ -0,0 +1,47 @@
+; RUN: opt -instcombine -S %s | FileCheck %s
+
+; Make sure we collapse the fences in this case
+
+; CHECK-LABEL: define void @tinkywinky
+; CHECK-NEXT:   fence seq_cst
+; CHECK-NEXT:   fence singlethread acquire
+; CHECK-NEXT:   ret void
+; CHECK-NEXT: }
+
+define void @tinkywinky() {
+  fence seq_cst
+  fence seq_cst
+  fence seq_cst
+  fence singlethread acquire
+  fence singlethread acquire
+  fence singlethread acquire
+  ret void
+}
+
+; CHECK-LABEL: define void @dipsy
+; CHECK-NEXT:   fence seq_cst
+; CHECK-NEXT:   fence singlethread seq_cst
+; CHECK-NEXT:   ret void
+; CHECK-NEXT: }
+
+define void @dipsy() {
+  fence seq_cst
+  fence singlethread seq_cst
+  ret void
+}
+
+; CHECK-LABEL: define void @patatino
+; CHECK-NEXT:   fence acquire
+; CHECK-NEXT:   fence seq_cst
+; CHECK-NEXT:   fence acquire
+; CHECK-NEXT:   fence seq_cst
+; CHECK-NEXT:   ret void
+; CHECK-NEXT: }
+
+define void @patatino() {
+  fence acquire
+  fence seq_cst
+  fence acquire
+  fence seq_cst
+  ret void
+}