MIPS: Fix r21780 - “Fixed flooring division by a power of 2, once again...”

src/mips/lithium-codegen-mips.cc

 // Copyright 2012 the V8 project authors. All rights reserved.7
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1309 matching lines @@
 
   // If the divisor is positive, things are easy: There can be no deopts and we
   // can simply do an arithmetic right shift.
   uint16_t shift = WhichPowerOf2Abs(divisor);
   if (divisor > 1) {
     __ sra(result, dividend, shift);
     return;
   }
 
   // If the divisor is negative, we have to negate and handle edge cases.
-  if (instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
-    // divident can be the same register as result so save the value of it
-    // for checking overflow.
-    __ Move(scratch, dividend);
-  }
+
+  // divident can be the same register as result so save the value of it
+  // for checking overflow.
+  __ Move(scratch, dividend);
+
   __ Subu(result, zero_reg, dividend);
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     DeoptimizeIf(eq, instr->environment(), result, Operand(zero_reg));
   }
 
   // Dividing by -1 is basically negation, unless we overflow.
-  __ Xor(at, scratch, result);
+  __ Xor(scratch, scratch, result);
   if (divisor == -1) {
     if (instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
       DeoptimizeIf(ge, instr->environment(), at, Operand(zero_reg));
     }
     return;
   }
 
   // If the negation could not overflow, simply shifting is OK.
   if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
     __ sra(result, result, shift);
     return;
   }
 
   Label no_overflow, done;
-  __ Branch(&no_overflow, lt, at, Operand(zero_reg));
+  __ Branch(&no_overflow, lt, scratch, Operand(zero_reg));
   __ li(result, Operand(kMinInt / divisor));
   __ Branch(&done);
   __ bind(&no_overflow);
   __ sra(result, result, shift);
   __ bind(&done);
 }
 
 
 void LCodeGen::DoFlooringDivByConstI(LFlooringDivByConstI* instr) {
   Register dividend = ToRegister(instr->dividend());
@@ skipping 4524 matching lines @@
   __ li(at, scope_info);
   __ Push(at, ToRegister(instr->function()));
   CallRuntime(Runtime::kHiddenPushBlockContext, 2, instr);
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal