[MachineLICM] Add test case showing load hoisted across memory barrier.

(cherry picked from commit a9b3ec1)

Author: fhahn

llvm/test/CodeGen/AArch64/machine-licm-hoist-load.ll

@@ -497,6 +497,35 @@ for.exit:                                 ; preds = %for.body
   ret i64 %spec.select
 }
 
+@a = external local_unnamed_addr global i32, align 4
+
+; FIXME: Load hoisted out of the loop across memory barriers.
+define i32 @load_between_memory_barriers() {
+; CHECK-LABEL: load_between_memory_barriers:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    adrp x8, :got:a
+; CHECK-NEXT:    ldr x8, [x8, :got_lo12:a]
+; CHECK-NEXT:    ldr w0, [x8]
+; CHECK-NEXT:  .LBB8_1: // %loop
+; CHECK-NEXT:    // =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    //MEMBARRIER
+; CHECK-NEXT:    //MEMBARRIER
+; CHECK-NEXT:    cbz w0, .LBB8_1
+; CHECK-NEXT:  // %bb.2: // %exit
+; CHECK-NEXT:    ret
+  br label %loop
+
+loop:
+  fence syncscope("singlethread") acq_rel
+  %l = load i32, ptr @a, align 4
+  fence syncscope("singlethread") acq_rel
+  %c = icmp eq i32 %l, 0
+  br i1 %c, label %loop, label %exit
+
+exit:
+  ret i32 %l
+}
+
 declare i32 @bcmp(ptr, ptr, i64)
 declare i32 @memcmp(ptr, ptr, i64)
 declare void @func()