Adds back arm ldrex strex.

runtime/vm/assembler_arm_test.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/assembler.h"
 #include "vm/cpu.h"
 #include "vm/os.h"
@@ skipping 648 matching lines @@
 }
 
 
 ASSEMBLER_TEST_RUN(LoadStore, test) {
   EXPECT(test != NULL);
   typedef int (*LoadStore)() DART_UNUSED;
   EXPECT_EQ(123, EXECUTE_TEST_CODE_INT32(LoadStore, test->entry()));
 }
 
 
+ASSEMBLER_TEST_GENERATE(Semaphore, assembler) {
+  if (TargetCPUFeatures::arm_version() == ARMv5TE) {
+    __ mov(R0, Operand(42));
+    __ bx(LR);
+  } else {
+    __ mov(R0, Operand(40));
+    __ mov(R1, Operand(42));
+    __ Push(R0);
+    Label retry;
+    __ Bind(&retry);
+    __ ldrex(R0, SP);
+    __ strex(IP, R1, SP);  // IP == 0, success
+    __ tst(IP, Operand(0));
+    __ b(&retry, NE);  // NE if context switch occurred between ldrex and strex.
+    __ Pop(R0);  // 42
+    __ bx(LR);
+  }
+}
+
+
+ASSEMBLER_TEST_RUN(Semaphore, test) {
+  EXPECT(test != NULL);
+  typedef int (*Semaphore)();
+  EXPECT_EQ(42, EXECUTE_TEST_CODE_INT32(Semaphore, test->entry()));
+}
+
+
+ASSEMBLER_TEST_GENERATE(FailedSemaphore, assembler) {
+  if (TargetCPUFeatures::arm_version() == ARMv5TE) {
+    __ mov(R0, Operand(41));
+    __ bx(LR);
+  } else {
+    __ mov(R0, Operand(40));
+    __ mov(R1, Operand(42));
+    __ Push(R0);
+    __ ldrex(R0, SP);
+    __ clrex();  // Simulate a context switch.
+    __ strex(IP, R1, SP);  // IP == 1, failure
+    __ Pop(R0);  // 40
+    __ add(R0, R0, Operand(IP));
+    __ bx(LR);
+  }
+}
+
+
+ASSEMBLER_TEST_RUN(FailedSemaphore, test) {
+  EXPECT(test != NULL);
+  typedef int (*FailedSemaphore)();
+  EXPECT_EQ(41, EXECUTE_TEST_CODE_INT32(FailedSemaphore, test->entry()));
+}
+
+
 ASSEMBLER_TEST_GENERATE(AddSub, assembler) {
   __ mov(R1, Operand(40));
   __ sub(R1, R1, Operand(2));
   __ add(R0, R1, Operand(4));
   __ rsbs(R0, R0, Operand(100));
   __ rsc(R0, R0, Operand(100));
   __ bx(LR);
 }
 
 
@@ skipping 3397 matching lines @@
   __ StoreIntoObject(R2,
                      FieldAddress(R2, GrowableObjectArray::data_offset()),
                      R1);
   __ PopList((1 << CTX) | (1 << LR));
   __ Ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM