MIPS: Fix debug mode webkit failures.

* Handles SMI case in EmitLoadRegister correctly.
* Fix minor mistake in the assembler.

BUG=v8:2808
TEST=webkit/dfg-dead-min-two-args,webkit/fast/js/excessive-comma-usage

Review URL: https://codereview.chromium.org/20801003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15914 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/assembler-mips.cc

@@ -1347,7 +1347,7 @@ void Assembler::rotrv(Register rd, Register rt, Register rs) {
 // Helper for base-reg + offset, when offset is larger than int16.
 void Assembler::LoadRegPlusOffsetToAt(const MemOperand& src) {
   ASSERT(!src.rm().is(at));
-  lui(at, src.offset_ >> kLuiShift);
+  lui(at, (src.offset_ >> kLuiShift) & kImm16Mask);
   ori(at, at, src.offset_ & kImm16Mask);  // Load 32-bit offset.
   addu(at, at, src.rm());  // Add base register.
 }

src/mips/lithium-codegen-mips.cc

@@ -407,6 +407,9 @@ Register LCodeGen::EmitLoadRegister(LOperand* op, Register scratch) {
     if (r.IsInteger32()) {
       ASSERT(literal->IsNumber());
       __ li(scratch, Operand(static_cast<int32_t>(literal->Number())));
+    } else if (r.IsSmi()) {
+      ASSERT(constant->HasSmiValue());
+      __ li(scratch, Operand(Smi::FromInt(constant->Integer32Value())));
     } else if (r.IsDouble()) {
       Abort("EmitLoadRegister: Unsupported double immediate.");
     } else {