MIPS: Tweaked FlooringDiv back to TruncatingDiv again.

Port r20048 (8953785)

Original commit message:
This is a first step towards getting the flooring division by a
constant working again (which will be a separate CL).

BUG=
R=plind44@gmail.com

Review URL: https://codereview.chromium.org/203443009

Patch from Balazs Kilvady <kilvadyb@homejinni.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20082 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/mips/lithium-codegen-mips.cc

@@ -1111,9 +1111,7 @@ void LCodeGen::DoModByConstI(LModByConstI* instr) {
     return;
   }
 
-  __ FlooringDiv(result, dividend, Abs(divisor));
-  __ srl(at, dividend, 31);
-  __ Addu(result, result, at);
+  __ TruncatingDiv(result, dividend, Abs(divisor));
   __ Mul(result, result, Operand(Abs(divisor)));
   __ Subu(result, dividend, Operand(result));
 
@@ -1230,9 +1228,7 @@ void LCodeGen::DoDivByConstI(LDivByConstI* instr) {
     DeoptimizeIf(eq, instr->environment(), dividend, Operand(zero_reg));
   }
 
-  __ FlooringDiv(result, dividend, Abs(divisor));
-  __ srl(at, dividend, 31);
-  __ Addu(result, result, Operand(at));
+  __ TruncatingDiv(result, dividend, Abs(divisor));
   if (divisor < 0) __ Subu(result, zero_reg, result);
 
   if (!hdiv->CheckFlag(HInstruction::kAllUsesTruncatingToInt32)) {
@@ -1371,7 +1367,8 @@ void LCodeGen::DoFlooringDivByConstI(LFlooringDivByConstI* instr) {
     DeoptimizeIf(eq, instr->environment(), dividend, Operand(zero_reg));
   }
 
-  __ FlooringDiv(result, dividend, divisor);
+  // TODO(svenpanne) Add correction terms.
+  __ TruncatingDiv(result, dividend, divisor);
 }
 
 

src/mips/macro-assembler-mips.cc

@@ -5723,9 +5723,9 @@ void CodePatcher::ChangeBranchCondition(Condition cond) {
 }
 
 
-void MacroAssembler::FlooringDiv(Register result,
-                                 Register dividend,
-                                 int32_t divisor) {
+void MacroAssembler::TruncatingDiv(Register result,
+                                   Register dividend,
+                                   int32_t divisor) {
   ASSERT(!dividend.is(result));
   ASSERT(!dividend.is(at));
   ASSERT(!result.is(at));
@@ -5739,9 +5739,9 @@ void MacroAssembler::FlooringDiv(Register result,
   if (divisor < 0 && ms.multiplier() > 0) {
     Subu(result, result, Operand(dividend));
   }
-  if (ms.shift() > 0) {
-    sra(result, result, ms.shift());
-  }
+  if (ms.shift() > 0) sra(result, result, ms.shift());
+  srl(at, dividend, 31);
+  Addu(result, result, Operand(at));
 }
 
 

src/mips/macro-assembler-mips.h

@@ -1304,9 +1304,9 @@ const Operand& rt = Operand(zero_reg), BranchDelaySlot bd = PROTECT
     return code_object_;
   }
 
-  // Emit code for a flooring division by a constant. The dividend register is
+  // Emit code for a truncating division by a constant. The dividend register is
   // unchanged and at gets clobbered. Dividend and result must be different.
-  void FlooringDiv(Register result, Register dividend, int32_t divisor);
+  void TruncatingDiv(Register result, Register dividend, int32_t divisor);
 
   // -------------------------------------------------------------------------
   // StatsCounter support.