Adds macros to the MIPS assembler for detecting overflow.

runtime/vm/assembler_mips_test.cc

Index: runtime/vm/assembler_mips_test.cc
===================================================================
--- runtime/vm/assembler_mips_test.cc	(revision 20999)
+++ runtime/vm/assembler_mips_test.cc	(working copy)
@@ -1041,6 +1041,64 @@
   EXPECT_EQ(42, EXECUTE_TEST_CODE_INT32(SimpleCode, test->entry()));
 }
 
+
+ASSEMBLER_TEST_GENERATE(AddOverflow_detect, assembler) {
+  Label error, success;

[regis, 2013/04/05 23:23:45]

"success" is actually "done".

[zra, 2013/04/06 00:04:19]

Done.

+  __ LoadImmediate(V0, 1);  // Success value.
+
+  __ LoadImmediate(T0, 0x7fffffff);
+  __ LoadImmediate(T1, 1);
+  __ AdduDetectOverflow(T2, T1, T0, T3);
+  __ bgez(T3, &error);  // INT_MAX + 1 overflows.
+
+  __ LoadImmediate(T0, 0x7fffffff);
+  __ LoadImmediate(T1, 0x7fffffff);
+  __ AdduDetectOverflow(T2, T1, T0, T3);
+  __ bgez(T3, &error);  // INT_MAX + INT_MAX overflows.
+
+  __ LoadImmediate(T0, 0x7fffffff);
+  __ LoadImmediate(T1, -1);
+  __ AdduDetectOverflow(T2, T1, T0, T3);
+  __ bltz(T3, &error);  // INT_MAX - 1 does not overflow.
+
+  __ LoadImmediate(T0, -1);
+  __ LoadImmediate(T1, 1);
+  __ AdduDetectOverflow(T2, T1, T0, T3);
+  __ bltz(T3, &error);  // -1 + 1 does not overflow.
+
+  __ LoadImmediate(T0, 123456);
+  __ LoadImmediate(T1, 654321);
+  __ AdduDetectOverflow(T2, T1, T0, T3);
+  __ bltz(T3, &error);  // 123456 + 654321 does not overflow.
+
+  __ LoadImmediate(T0, 0x80000000);
+  __ LoadImmediate(T1, -1);
+  __ AdduDetectOverflow(T2, T1, T0, T3);
+  __ bgez(T3, &error);  // INT_MIN - 1 overflows.
+
+  __ LoadImmediate(T0, 0x80000000);
+  __ LoadImmediate(T1, 0x80000000);
+  __ AdduDetectOverflow(T2, T1, T0, T3);
+  __ bgez(T3, &error);  // INT_MIN + INT_MIN overflows.
+
+  __ LoadImmediate(T0, -123456);
+  __ LoadImmediate(T1, -654321);
+  __ AdduDetectOverflow(T2, T1, T0, T3);
+  __ bltz(T3, &error);  // -123456 + -654321 does not overflow.
+
+  __ b(&success);
+  __ Bind(&error);
+  __ mov(V0, ZR);
+  __ Bind(&success);
+  __ Ret();
+}
+
+
+ASSEMBLER_TEST_RUN(AddOverflow_detect, test) {
+  typedef int (*SimpleCode)();
+  EXPECT_EQ(1, EXECUTE_TEST_CODE_INT32(SimpleCode, test->entry()));
+}
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_MIPS