Imported Upstream version 6.0.0.172

Former-commit-id: f3cc9b82f3e5bd8f0fd3ebc098f789556b44e9cd

external/llvm/test/CodeGen/ARM/swift-atomics.ll

@@ -0,0 +1,51 @@
+; RUN: llc -mtriple=armv7-apple-ios6.0 -mcpu=swift < %s | FileCheck %s
+; RUN: llc -mtriple=armv7-apple-ios6.0 < %s | FileCheck %s --check-prefix=CHECK-STRICT-ATOMIC
+
+; Release operations only need the store barrier provided by a "dmb ishst",
+
+define void @test_store_release(i32* %p, i32 %v) {
+; CHECK-LABEL: test_store_release:
+; CHECK: dmb ishst
+; CHECK: str
+
+; CHECK-STRICT-ATOMIC-LABEL: test_store_release:
+; CHECK-STRICT-ATOMIC: dmb {{ish$}}
+  store atomic i32 %v, i32* %p release, align 4
+  ret void
+}
+
+; However, if sequential consistency is needed *something* must ensure a release
+; followed by an acquire does not get reordered. In that case a "dmb ishst" is
+; not adequate.
+define i32 @test_seq_cst(i32* %p, i32 %v) {
+; CHECK-LABEL: test_seq_cst:
+; CHECK: dmb ishst
+; CHECK: str
+; CHECK: dmb {{ish$}}
+; CHECK: ldr
+; CHECK: dmb {{ish$}}
+
+; CHECK-STRICT-ATOMIC-LABEL: test_seq_cst:
+; CHECK-STRICT-ATOMIC: dmb {{ish$}}
+; CHECK-STRICT-ATOMIC: str
+; CHECK-STRICT-ATOMIC: dmb {{ish$}}
+; CHECK-STRICT-ATOMIC: ldr
+; CHECK-STRICT-ATOMIC: dmb {{ish$}}
+
+  store atomic i32 %v, i32* %p seq_cst, align 4
+  %val = load atomic i32, i32* %p seq_cst, align 4
+  ret i32 %val
+}
+
+; Also, pure acquire operations should definitely not have an ishst barrier.
+
+define i32 @test_acq(i32* %addr) {
+; CHECK-LABEL: test_acq:
+; CHECK: ldr
+; CHECK: dmb {{ish$}}
+
+; CHECK-STRICT-ATOMIC-LABEL: test_acq:
+; CHECK-STRICT-ATOMIC: dmb {{ish$}}
+  %val = load atomic i32, i32* %addr acquire, align 4
+  ret i32 %val
+}