Handle non-constant divisor in MathFloorOfDiv, on ia32/x64

src/ia32/lithium-codegen-ia32.cc

Index: src/ia32/lithium-codegen-ia32.cc
===================================================================
--- src/ia32/lithium-codegen-ia32.cc	(revision 13258)
+++ src/ia32/lithium-codegen-ia32.cc	(working copy)
@@ -1212,7 +1212,7 @@
 
 
 void LCodeGen::DoDivI(LDivI* instr) {
-  if (instr->hydrogen()->HasPowerOf2Divisor()) {
+  if (!instr->is_flooring() && instr->hydrogen()->HasPowerOf2Divisor()) {
     Register dividend = ToRegister(instr->left());
     int32_t divisor =
         HConstant::cast(instr->hydrogen()->right())->Integer32Value();
@@ -1259,13 +1259,13 @@
 
   // Check for x / 0.
   Register right_reg = ToRegister(right);
-  if (instr->hydrogen()->CheckFlag(HValue::kCanBeDivByZero)) {
+  if (instr->hydrogen_value()->CheckFlag(HValue::kCanBeDivByZero)) {
     __ test(right_reg, ToOperand(right));
     DeoptimizeIf(zero, instr->environment());
   }
 
   // Check for (0 / -x) that will produce negative zero.
-  if (instr->hydrogen()->CheckFlag(HValue::kBailoutOnMinusZero)) {
+  if (instr->hydrogen_value()->CheckFlag(HValue::kBailoutOnMinusZero)) {
     Label left_not_zero;
     __ test(left_reg, Operand(left_reg));
     __ j(not_zero, &left_not_zero, Label::kNear);
@@ -1275,7 +1275,7 @@
   }
 
   // Check for (kMinInt / -1).
-  if (instr->hydrogen()->CheckFlag(HValue::kCanOverflow)) {
+  if (instr->hydrogen_value()->CheckFlag(HValue::kCanOverflow)) {
     Label left_not_min_int;
     __ cmp(left_reg, kMinInt);
     __ j(not_zero, &left_not_min_int, Label::kNear);
@@ -1288,9 +1288,19 @@
   __ cdq();
   __ idiv(right_reg);
 
-  // Deoptimize if remainder is not 0.
-  __ test(edx, Operand(edx));
-  DeoptimizeIf(not_zero, instr->environment());
+  if (!instr->is_flooring()) {
+    // Deoptimize if remainder is not 0.
+    __ test(edx, Operand(edx));
+    DeoptimizeIf(not_zero, instr->environment());
+  } else {
+    Label done;

[Yang, 2012/12/27 14:41:53]

Tests, especially targetting this code path, would be really great. There are
many cases to test: positive/negative left and right, 0 in quotient and/or
remainder, etc.

+    __ test(edx, edx);
+    __ j(zero, &done, Label::kNear);
+    __ xor_(edx, right_reg);
+    __ sar(edx, 31);
+    __ add(eax, edx);
+    __ bind(&done);
+  }
 }