SelectionDAG: skip barriers for unordered atomic operations

Unordered is strictly weaker than monotonic, so if the latter doesn't have any
barriers then the former certainly shouldn't.

rdar://problem/16548260

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209901 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -3570,12 +3570,12 @@ static SDValue InsertFenceForAtomic(SDValue Chain, AtomicOrdering Order,
   if (Before) {
     if (Order == AcquireRelease || Order == SequentiallyConsistent)
       Order = Release;
-    else if (Order == Acquire || Order == Monotonic)
+    else if (Order == Acquire || Order == Monotonic || Order == Unordered)
       return Chain;
   } else {
     if (Order == AcquireRelease)
       Order = Acquire;
-    else if (Order == Release || Order == Monotonic)
+    else if (Order == Release || Order == Monotonic || Order == Unordered)
       return Chain;
   }
   SDValue Ops[3];

test/CodeGen/ARM/atomic-load-store.ll

@@ -5,13 +5,13 @@
 ; RUN: llc < %s -mtriple=armv4-apple-ios | FileCheck %s -check-prefix=ARMV4
 
 define void @test1(i32* %ptr, i32 %val1) {
-; ARM: test1
+; ARM-LABEL: test1
 ; ARM: dmb {{ish$}}
 ; ARM-NEXT: str
 ; ARM-NEXT: dmb {{ish$}}
-; THUMBONE: test1
+; THUMBONE-LABEL: test1
 ; THUMBONE: __sync_lock_test_and_set_4
-; THUMBTWO: test1
+; THUMBTWO-LABEL: test1
 ; THUMBTWO: dmb {{ish$}}
 ; THUMBTWO-NEXT: str
 ; THUMBTWO-NEXT: dmb {{ish$}}
@@ -20,12 +20,12 @@ define void @test1(i32* %ptr, i32 %val1) {
 }
 
 define i32 @test2(i32* %ptr) {
-; ARM: test2
+; ARM-LABEL: test2
 ; ARM: ldr
 ; ARM-NEXT: dmb {{ish$}}
-; THUMBONE: test2
+; THUMBONE-LABEL: test2
 ; THUMBONE: __sync_val_compare_and_swap_4
-; THUMBTWO: test2
+; THUMBTWO-LABEL: test2
 ; THUMBTWO: ldr
 ; THUMBTWO-NEXT: dmb {{ish$}}
   %val = load atomic i32* %ptr seq_cst, align 4
@@ -33,22 +33,35 @@ define i32 @test2(i32* %ptr) {
 }
 
 define void @test3(i8* %ptr1, i8* %ptr2) {
-; ARM: test3
+; ARM-LABEL: test3
+; ARM-NOT: dmb
 ; ARM: ldrb
+; ARM-NOT: dmb
 ; ARM: strb
-; THUMBTWO: test3
+; ARM-NOT: dmb
+; ARM: bx lr
+
+; THUMBTWO-LABEL: test3
+; THUMBTWO-NOT: dmb
 ; THUMBTWO: ldrb
+; THUMBTWO-NOT: dmb
 ; THUMBTWO: strb
-; THUMBONE: test3
+; THUMBTWO-NOT: dmb
+; THUMBTWO: bx lr
+
+; THUMBONE-LABEL: test3
+; THUMBONE-NOT: dmb
 ; THUMBONE: ldrb
+; THUMBONE-NOT: dmb
 ; THUMBONE: strb
+; THUMBONE-NOT: dmb
   %val = load atomic i8* %ptr1 unordered, align 1
   store atomic i8 %val, i8* %ptr2 unordered, align 1
   ret void
 }
 
 define void @test4(i8* %ptr1, i8* %ptr2) {
-; THUMBONE: test4
+; THUMBONE-LABEL: test4
 ; THUMBONE: ___sync_val_compare_and_swap_1
 ; THUMBONE: ___sync_lock_test_and_set_1
   %val = load atomic i8* %ptr1 seq_cst, align 1
@@ -57,14 +70,14 @@ define void @test4(i8* %ptr1, i8* %ptr2) {
 }
 
 define i64 @test_old_load_64bit(i64* %p) {
-; ARMV4: test_old_load_64bit
+; ARMV4-LABEL: test_old_load_64bit
 ; ARMV4: ___sync_val_compare_and_swap_8
   %1 = load atomic i64* %p seq_cst, align 8
   ret i64 %1
 }
 
 define void @test_old_store_64bit(i64* %p, i64 %v) {
-; ARMV4: test_old_store_64bit
+; ARMV4-LABEL: test_old_store_64bit
 ; ARMV4: ___sync_lock_test_and_set_8
   store atomic i64 %v, i64* %p seq_cst, align 8
   ret void