[wasm] Fix codegen issue for i64.add and i64.sub on ia32

test/cctest/wasm/test-run-wasm-64.cc

Index: test/cctest/wasm/test-run-wasm-64.cc
diff --git a/test/cctest/wasm/test-run-wasm-64.cc b/test/cctest/wasm/test-run-wasm-64.cc
index e217bb8e71e09db7e09ac4f5afd08634e2427ced..ff1bdc96ac90b21cbf1b619717a545c4dfa22617 100644
--- a/test/cctest/wasm/test-run-wasm-64.cc
+++ b/test/cctest/wasm/test-run-wasm-64.cc
@@ -136,6 +136,16 @@ WASM_EXEC_TEST(I64Add) {
   }
 }
 
+WASM_EXEC_TEST(I64AddRegress5800) {

[Mircea Trofin, 2017/01/18 21:01:56]

Elsewhere in cctest, we appear to have the naming pattern
"Regressxyz_somethingelse". 
Example (albeit this uses lower case rather than "Regress" like everywhere else)

./test-assembler-arm.cc:TEST(regress4292_b)

[Eric Holk, 2017/01/18 21:20:50]

Done.

+  REQUIRE(I64Add);
+  WasmRunner<int32_t> r(execution_mode);
+  BUILD(r, WASM_BLOCK(WASM_BR_IF(0, WASM_I64_EQZ(WASM_I64_ADD(
+                                        WASM_I64V(0), WASM_I64V(0x100000000)))),

[Mircea Trofin, 2017/01/18 21:01:56]

add comment explaining why you picked 0x100000000

maybe add a constant like kHasBit33On, and reuse in both tests.

[Eric Holk, 2017/01/18 21:20:50]

Done.

+                      WASM_RETURN1(WASM_I32V(0))),
+        WASM_I32V(0));
+  CHECK_EQ(0, r.Call());
+}
+
 WASM_EXEC_TEST(I64Sub) {
   REQUIRE(I64Sub);
   WasmRunner<int64_t, int64_t, int64_t> r(execution_mode);
@@ -145,6 +155,16 @@ WASM_EXEC_TEST(I64Sub) {
   }
 }
 
+WASM_EXEC_TEST(I64SubRegress5800) {
+  REQUIRE(I64Add);
+  WasmRunner<int32_t> r(execution_mode);
+  BUILD(r, WASM_BLOCK(WASM_BR_IF(0, WASM_I64_EQZ(WASM_I64_SUB(
+                                        WASM_I64V(0), WASM_I64V(0x100000000)))),
+                      WASM_RETURN1(WASM_I32V(0))),
+        WASM_I32V(0));
+  CHECK_EQ(0, r.Call());
+}
+
 WASM_EXEC_TEST(I64AddUseOnlyLowWord) {
   REQUIRE(I64Add);
   REQUIRE(I32ConvertI64);