MIPS: Fixed flooring division by a power of 2, once again...

src/mips/lithium-codegen-mips.cc

Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc b/src/mips/lithium-codegen-mips.cc
index 65fe1aa910f1243650e64e761524d9a8b7ede4da..1b2dec04416480659edd618642d88277ccfef9a6 100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -1309,8 +1309,8 @@ 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) {
@@ -1328,6 +1328,8 @@ void LCodeGen::DoFlooringDivByPowerOf2I(LFlooringDivByPowerOf2I* instr) {
 
   // 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);
@@ -1335,16 +1337,18 @@ void LCodeGen::DoFlooringDivByPowerOf2I(LFlooringDivByPowerOf2I* instr) {
     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;
   }
 
@@ -1353,7 +1357,7 @@ void LCodeGen::DoFlooringDivByPowerOf2I(LFlooringDivByPowerOf2I* instr) {
   __ li(result, Operand(kMinInt / divisor));
   __ Branch(&done);
   __ bind(&no_overflow);
-  __ sra(result, dividend, shift);
+  __ sra(result, result, shift);
   __ bind(&done);
 }