MIPS: Generate TypedArrayInitialize builtin in hydrogen.

Port r18059 (b2849c3)

BUG=
R=dslomov@chromium.org, gergely@homejinni.com

Review URL: https://codereview.chromium.org/86053003

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18066 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/lithium-mips.cc

@@ -1587,6 +1587,15 @@ LInstruction* LChunkBuilder::DoAdd(HAdd* instr) {
       result = AssignEnvironment(result);
     }
     return result;
+  } else if (instr->representation().IsExternal()) {
+    ASSERT(instr->left()->representation().IsExternal());
+    ASSERT(instr->right()->representation().IsInteger32());
+    ASSERT(!instr->CheckFlag(HValue::kCanOverflow));
+    LOperand* left = UseRegisterAtStart(instr->left());
+    LOperand* right = UseOrConstantAtStart(instr->right());
+    LAddI* add = new(zone()) LAddI(left, right);
+    LInstruction* result = DefineAsRegister(add);
+    return result;
   } else if (instr->representation().IsDouble()) {
     if (kArchVariant == kMips32r2) {
       if (instr->left()->IsMul())