Fixed constant folding in HMod.

We have to check for overflow before attempting to do a modulo operation,
otherwise Crankshaft itself segfaults on some platforms, e.g. ia32. Added tests
even for division, where the problem doesn't show up, just to be sure...

R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/14617014

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14629 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-instructions.cc

@@ -3341,6 +3341,9 @@ HInstruction* HMod::New(
     if (c_left->HasInteger32Value() && c_right->HasInteger32Value()) {
       int32_t dividend = c_left->Integer32Value();
       int32_t divisor = c_right->Integer32Value();
+      if (dividend == kMinInt && divisor == -1) {
+        return H_CONSTANT_DOUBLE(-0.0);
+      }
       if (divisor != 0) {
         int32_t res = dividend % divisor;
         if ((res == 0) && (dividend < 0)) {

test/mjsunit/constant-folding-2.js

@@ -256,3 +256,12 @@ test(function stringCharAt() {
   assertEquals("b", "abc".charAt(1.1));
   assertEquals("", "abc".charAt(4.1));
 });
+
+
+test(function int32Mod() {
+  assertEquals(-0, -2147483648 % (-1));
+});
+
+test(function int32Div() {
+  assertEquals(2147483648, -2147483648 / (-1));
+});