Handle flooring division in LCodeGen::DoDivByConstI on ARM, too.

We should really split up the Lithium instruction, but this will be
done in some future cleanup CL.

Removed some "const"s for local variables on the way, they don't really
help us much and just clutter up the code.

R=ulan@chromium.org

Review URL: https://codereview.chromium.org/196603004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19850 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-codegen-arm.cc

@@ -1365,9 +1365,9 @@ void LCodeGen::DoDivByConstI(LDivByConstI* instr) {
 
 void LCodeGen::DoDivI(LDivI* instr) {
   HBinaryOperation* hdiv = instr->hydrogen();
-  const Register left = ToRegister(instr->left());
-  const Register right = ToRegister(instr->right());
-  const Register result = ToRegister(instr->result());
+  Register left = ToRegister(instr->left());
+  Register right = ToRegister(instr->right());
+  Register result = ToRegister(instr->result());
 
   // Check for x / 0.
   if (hdiv->CheckFlag(HValue::kCanBeDivByZero)) {
@@ -1402,17 +1402,9 @@ void LCodeGen::DoDivI(LDivI* instr) {
   if (CpuFeatures::IsSupported(SUDIV)) {
     CpuFeatureScope scope(masm(), SUDIV);
     __ sdiv(result, left, right);
-
-    if (!hdiv->CheckFlag(HValue::kAllUsesTruncatingToInt32)) {
-      // Compute remainder and deopt if it's not zero.
-      const Register remainder = scratch0();
-      __ mls(remainder, result, right, left);
-      __ cmp(remainder, Operand::Zero());
-      DeoptimizeIf(ne, instr->environment());
-    }
   } else {
-    const DoubleRegister vleft = ToDoubleRegister(instr->temp());
-    const DoubleRegister vright = double_scratch0();
+    DoubleRegister vleft = ToDoubleRegister(instr->temp());
+    DoubleRegister vright = double_scratch0();
     __ vmov(double_scratch0().low(), left);
     __ vcvt_f64_s32(vleft, double_scratch0().low());
     __ vmov(double_scratch0().low(), right);
@@ -1420,14 +1412,23 @@ void LCodeGen::DoDivI(LDivI* instr) {
     __ vdiv(vleft, vleft, vright);  // vleft now contains the result.
     __ vcvt_s32_f64(double_scratch0().low(), vleft);
     __ vmov(result, double_scratch0().low());
+  }
 
-    if (!hdiv->CheckFlag(HValue::kAllUsesTruncatingToInt32)) {
-      // Deopt if exact conversion to integer was not possible.
-      // Use vright as scratch register.
-      __ vcvt_f64_s32(double_scratch0(), double_scratch0().low());
-      __ VFPCompareAndSetFlags(vleft, double_scratch0());
-      DeoptimizeIf(ne, instr->environment());
-    }
+  if (hdiv->IsMathFloorOfDiv()) {
+    Label done;
+    Register remainder = scratch0();
+    __ mls(remainder, result, right, left);
+    __ cmp(remainder, Operand::Zero());
+    __ b(eq, &done);
+    __ eor(remainder, remainder, Operand(right));
+    __ add(result, result, Operand(remainder, ASR, 31));
+    __ bind(&done);
+  } else if (!hdiv->CheckFlag(HValue::kAllUsesTruncatingToInt32)) {
+    // Compute remainder and deopt if it's not zero.
+    Register remainder = scratch0();
+    __ mls(remainder, result, right, left);
+    __ cmp(remainder, Operand::Zero());
+    DeoptimizeIf(ne, instr->environment());
   }
 }