x86/x64 port of Math.floor(x/y) to use integer division for specific divisor

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
===================================================================
--- src/ia32/lithium-ia32.cc	(revision 11883)
+++ src/ia32/lithium-ia32.cc	(working copy)
@@ -1347,12 +1347,57 @@
 }
 
 
-LInstruction* LChunkBuilder::DoMathFloorOfDiv(HMathFloorOfDiv* instr) {
-  UNIMPLEMENTED();
+HValue* LChunkBuilder::SimplifiedDividendForMathFloorOfDiv(HValue* dividend) {
+  // A value with an integer representation does not need to be transformed.
+  if (dividend->representation().IsInteger32()) {
+    return dividend;
+  // A change from an integer32 can be replaced by the integer32 value.
+  } else if (dividend->IsChange() &&
+      HChange::cast(dividend)->from().IsInteger32()) {
+    return HChange::cast(dividend)->value();
+  }
   return NULL;
 }
 
 
+HValue* LChunkBuilder::SimplifiedDivisorForMathFloorOfDiv(HValue* divisor) {
+  if (divisor->IsConstant() &&
+      HConstant::cast(divisor)->HasInteger32Value()) {
+    HConstant* constant_val = HConstant::cast(divisor);
+    return constant_val->CopyToRepresentation(Representation::Integer32(),
+                                              divisor->block()->zone());
+  }
+  return NULL;
+}
+
+
+LInstruction* LChunkBuilder::DoMathFloorOfDiv(HMathFloorOfDiv* instr) {
+  HValue* right = instr->right();
+  ASSERT(right->IsConstant() && HConstant::cast(right)->HasInteger32Value());
+  LOperand* divisor = chunk_->DefineConstantOperand(HConstant::cast(right));
+  int32_t divisor_si = HConstant::cast(right)->Integer32Value();
+  if (divisor_si == 0) {
+    LOperand* dividend = UseRegister(instr->left());
+    return AssignEnvironment(DefineAsRegister(
+        new(zone()) LMathFloorOfDiv(dividend, divisor, NULL)));
+  } else if (IsPowerOf2(abs(divisor_si))) {
+    // use dividend as temp if divisor < 0 && divisor != -1
+    LOperand* dividend = divisor_si < -1 ? UseTempRegister(instr->left()) :
+                         UseRegisterAtStart(instr->left());
+    LInstruction* result = DefineAsRegister(
+        new(zone()) LMathFloorOfDiv(dividend, divisor, NULL));
+    return divisor_si < 0 ? AssignEnvironment(result) : result;
+  } else {
+    // needs edx:eax, plus a temp
+    LOperand* dividend = UseFixed(instr->left(), eax);
+    LOperand* temp = TempRegister();
+    LInstruction* result = DefineFixed(
+        new(zone()) LMathFloorOfDiv(dividend, divisor, temp), edx);
+    return divisor_si < 0 ? AssignEnvironment(result) : result;
+  }
+}
+
+
 LInstruction* LChunkBuilder::DoMod(HMod* instr) {
   if (instr->representation().IsInteger32()) {
     ASSERT(instr->left()->representation().IsInteger32());