MIPS: Increase sanity of integer division handling.

Port r15057 (c82c777)

Original commit message:
- In the INT32 BinaryOpStub, fix type feedback collection for DIV,
bringing it in line with other platforms.
- In Lithium codegen, emit proper inlined code, don't call the stub.
- Drive-by fix: assert appropriate CpuFeaturesScope for SDIV.

BUG=

Review URL: https://codereview.chromium.org/16857004
Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15127 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/code-stubs-mips.cc

@@ -2488,47 +2488,36 @@ void BinaryOpStub::GenerateInt32Stub(MacroAssembler* masm) {
             UNREACHABLE();
         }
 
-        if (op_ != Token::DIV) {
-          // These operations produce an integer result.
-          // Try to return a smi if we can.
-          // Otherwise return a heap number if allowed, or jump to type
-          // transition.
-
+        if (result_type_ <= BinaryOpIC::INT32) {
           Register except_flag = scratch2;
-          __ EmitFPUTruncate(kRoundToZero,
+          const FPURoundingMode kRoundingMode = op_ == Token::DIV ?
+              kRoundToMinusInf : kRoundToZero;
+          const CheckForInexactConversion kConversion = op_ == Token::DIV ?
+              kCheckForInexactConversion : kDontCheckForInexactConversion;
+          __ EmitFPUTruncate(kRoundingMode,
                              scratch1,
                              f10,
                              at,
                              f16,
-                             except_flag);
-
-          if (result_type_ <= BinaryOpIC::INT32) {
-            // If except_flag != 0, result does not fit in a 32-bit integer.
-            __ Branch(&transition, ne, except_flag, Operand(zero_reg));
-          }
-
-          // Check if the result fits in a smi.
-          __ Addu(scratch2, scratch1, Operand(0x40000000));
-          // If not try to return a heap number.
+                             except_flag,
+                             kConversion);
+          // If except_flag != 0, result does not fit in a 32-bit integer.
+          __ Branch(&transition, ne, except_flag, Operand(zero_reg));
+          // Try to tag the result as a Smi, return heap number on overflow.
+          __ SmiTagCheckOverflow(scratch1, scratch1, scratch2);
           __ Branch(&return_heap_number, lt, scratch2, Operand(zero_reg));
-          // Check for minus zero. Return heap number for minus zero if
-          // double results are allowed; otherwise transition.
+          // Check for minus zero, transition in that case (because we need
+          // to return a heap number).
           Label not_zero;
+          ASSERT(kSmiTag == 0);
           __ Branch(&not_zero, ne, scratch1, Operand(zero_reg));
           __ mfc1(scratch2, f11);
           __ And(scratch2, scratch2, HeapNumber::kSignMask);
-          __ Branch(result_type_ <= BinaryOpIC::INT32 ? &transition
-                    : &return_heap_number,
-                    ne,
-                    scratch2,
-                    Operand(zero_reg));
+          __ Branch(&transition, ne, scratch2, Operand(zero_reg));
           __ bind(&not_zero);
 
-          // Tag the result and return.
           __ Ret(USE_DELAY_SLOT);
-          __ SmiTag(v0, scratch1);  // SmiTag emits one instruction.
-        } else {
-          // DIV just falls through to allocating a heap number.
+          __ mov(v0, scratch1);
         }
 
         __ bind(&return_heap_number);

src/mips/lithium-mips.cc

@@ -1360,15 +1360,10 @@ LInstruction* LChunkBuilder::DoDiv(HDiv* instr) {
   if (instr->representation().IsDouble()) {
     return DoArithmeticD(Token::DIV, instr);
   } else if (instr->representation().IsInteger32()) {
-    // TODO(1042) The fixed register allocation
-    // is needed because we call TypeRecordingBinaryOpStub from
-    // the generated code, which requires registers a0
-    // and a1 to be used. We should remove that
-    // when we provide a native implementation.
-    LOperand* dividend = UseFixed(instr->left(), a0);
-    LOperand* divisor = UseFixed(instr->right(), a1);
-    return AssignEnvironment(AssignPointerMap(
-             DefineFixed(new(zone()) LDivI(dividend, divisor), v0)));
+    LOperand* dividend = UseRegister(instr->left());
+    LOperand* divisor = UseRegister(instr->right());
+    LDivI* div = new(zone()) LDivI(dividend, divisor);
+    return AssignEnvironment(DefineAsRegister(div));
   } else {
     return DoArithmeticT(Token::DIV, instr);
   }