Implement flooring division by a constant via truncating division by a constant.

src/x64/lithium-codegen-x64.cc

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     return;
   }
 
   // Check for (0 / -x) that will produce negative zero.
   HMathFloorOfDiv* hdiv = instr->hydrogen();
   if (hdiv->CheckFlag(HValue::kBailoutOnMinusZero) && divisor < 0) {
     __ testl(dividend, dividend);
     DeoptimizeIf(zero, instr->environment());
   }
 
-  // TODO(svenpanne) Add correction terms.
-  __ TruncatingDiv(dividend, divisor);
+  // Easy case: We need no dynamic check for the dividend and the flooring
+  // division is the same as the truncating division.
+  if ((divisor > 0 && !hdiv->CheckFlag(HValue::kLeftCanBeNegative)) ||
+      (divisor < 0 && !hdiv->CheckFlag(HValue::kLeftCanBePositive))) {
+    __ TruncatingDiv(dividend, Abs(divisor));
+    if (divisor < 0) __ negl(rdx);
+    return;
+  }
+
+  // In the general case we may need to adjust before and after the truncating
+  // division to get a flooring division.
+  Register temp = ToRegister(instr->temp3());
+  ASSERT(!temp.is(dividend) && !temp.is(rax) && !temp.is(rdx));
+  Label needs_adjustment, done;
+  __ cmpl(dividend, Immediate(0));
+  __ j(divisor > 0 ? less : greater, &needs_adjustment, Label::kNear);
+  __ TruncatingDiv(dividend, Abs(divisor));
+  if (divisor < 0) __ negl(rdx);
+  __ jmp(&done, Label::kNear);
+  __ bind(&needs_adjustment);
+  __ leal(temp, Operand(dividend, divisor > 0 ? 1 : -1));
+  __ TruncatingDiv(temp, Abs(divisor));
+  if (divisor < 0) __ negl(rdx);
+  __ decl(rdx);
+  __ bind(&done);
 }
 
 
 void LCodeGen::DoDivByPowerOf2I(LDivByPowerOf2I* instr) {
   Register dividend = ToRegister(instr->dividend());
   int32_t divisor = instr->divisor();
   Register result = ToRegister(instr->result());
   ASSERT(divisor == kMinInt || (divisor != 0 && IsPowerOf2(Abs(divisor))));
   ASSERT(!result.is(dividend));
 
@@ skipping 4461 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64