MIPS: 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 1291 matching lines @@
   ASSERT(addend.is(ToDoubleRegister(instr->result())));
 
   __ madd_d(addend, addend, multiplier, multiplicand);
 }
 
 
 void LCodeGen::DoFlooringDivByPowerOf2I(LFlooringDivByPowerOf2I* instr) {
   Register dividend = ToRegister(instr->dividend());
   Register result = ToRegister(instr->result());
   int32_t divisor = instr->divisor();
-  Register scratch = scratch0();
-  ASSERT(!scratch.is(dividend));
+  Register scratch = result.is(dividend) ? scratch0() : dividend;
+  ASSERT(!result.is(dividend) || !scratch.is(dividend));
 
   // If the divisor is 1, return the dividend.
   if (divisor == 1) {
     __ Move(result, dividend);
     return;
   }
 
   // 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);
   }
   __ Subu(result, zero_reg, dividend);
   if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     DeoptimizeIf(eq, instr->environment(), result, Operand(zero_reg));
   }
 
-  // If the negation could not overflow, simply shifting is OK.
-  if (!instr->hydrogen()->CheckFlag(HValue::kLeftCanBeMinInt)) {
-    __ sra(result, dividend, shift);
-    return;
-  }
-
   // Dividing by -1 is basically negation, unless we overflow.
   __ Xor(at, scratch, result);
   if (divisor == -1) {
-    DeoptimizeIf(ge, instr->environment(), at, Operand(zero_reg));
+    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));
   __ li(result, Operand(kMinInt / divisor));
   __ Branch(&done);
   __ bind(&no_overflow);
-  __ sra(result, dividend, shift);
+  __ sra(result, result, shift);
   __ bind(&done);
 }
 
 
 void LCodeGen::DoFlooringDivByConstI(LFlooringDivByConstI* instr) {
   Register dividend = ToRegister(instr->dividend());
   int32_t divisor = instr->divisor();
   Register result = ToRegister(instr->result());
   ASSERT(!dividend.is(result));
 
@@ skipping 4520 matching lines @@
   __ li(at, scope_info);
   __ Push(at, ToRegister(instr->function()));
   CallRuntime(Runtime::kHiddenPushBlockContext, 2, instr);
   RecordSafepoint(Safepoint::kNoLazyDeopt);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal