Handle non-power-of-2 divisors in division-like operations

src/a64/lithium-codegen-a64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1039 matching lines @@
 void LCodeGen::DeoptimizeIf(Condition cond, LEnvironment* environment) {
   DeoptimizeBranch(environment, static_cast<BranchType>(cond));
 }
 
 
 void LCodeGen::DeoptimizeIfZero(Register rt, LEnvironment* environment) {
   DeoptimizeBranch(environment, reg_zero, rt);
 }
 
 
+void LCodeGen::DeoptimizeIfNotZero(Register rt, LEnvironment* environment) {
+  DeoptimizeBranch(environment, reg_not_zero, rt);
+}
+
+
 void LCodeGen::DeoptimizeIfNegative(Register rt, LEnvironment* environment) {
   int sign_bit = rt.Is64Bits() ? kXSignBit : kWSignBit;
   DeoptimizeBranch(environment, reg_bit_set, rt, sign_bit);
 }
 
 
 void LCodeGen::DeoptimizeIfSmi(Register rt,
                                LEnvironment* environment) {
   DeoptimizeBranch(environment, reg_bit_clear, rt, MaskToBit(kSmiTagMask));
 }
@@ skipping 1533 matching lines @@
     __ Add(result, dividend, Operand(dividend, LSR, 31));
   } else {
     __ Mov(result, Operand(dividend, ASR, 31));
     __ Add(result, dividend, Operand(result, LSR, 32 - shift));
   }
   if (shift > 0) __ Mov(result, Operand(result, ASR, shift));
   if (divisor < 0) __ Neg(result, result);
 }
 
 
+void LCodeGen::DoDivByConstI(LDivByConstI* instr) {
+  Register dividend = ToRegister32(instr->dividend());
+  int32_t divisor = instr->divisor();
+  Register result = ToRegister32(instr->result());
+  ASSERT(!AreAliased(dividend, result));
+
+  if (divisor == 0) {
+    Deoptimize(instr->environment());
+    return;
+  }
+
+  // Check for (0 / -x) that will produce negative zero.
+  HDiv* hdiv = instr->hydrogen();
+  if (hdiv->CheckFlag(HValue::kBailoutOnMinusZero) &&
+      hdiv->left()->RangeCanInclude(0) && divisor < 0) {
+    __ Cmp(dividend, 0);

[m.m.capewell, 2014/03/07 11:37:29]

DeoptimizeIfZero()

+    DeoptimizeIf(eq, instr->environment());
+  }
+
+  __ FlooringDiv(result, dividend, Abs(divisor));
+  if (divisor < 0) __ Neg(result, result);
+
+  if (!hdiv->CheckFlag(HInstruction::kAllUsesTruncatingToInt32)) {
+    Register temp = ToRegister32(instr->temp());
+    ASSERT(!AreAliased(dividend, result, temp));
+    __ Sxtw(dividend.X(), dividend);
+    __ Mov(temp, divisor);
+    __ Smsubl(temp.X(), result, temp, dividend.X());
+    DeoptimizeIfNotZero(temp, instr->environment());
+  }
+}
+
+
 void LCodeGen::DoDivI(LDivI* instr) {
   Register dividend = ToRegister32(instr->left());
   Register divisor = ToRegister32(instr->right());
   Register result = ToRegister32(instr->result());
   HValue* hdiv = instr->hydrogen_value();
 
   // Issue the division first, and then check for any deopt cases whilst the
   // result is computed.
   __ Sdiv(result, dividend, divisor);
 
@@ skipping 1190 matching lines @@
       __ Mov(dividend, kMinInt / divisor);
       __ B(&done);
     }
   }
   __ bind(&not_kmin_int);
   __ Mov(dividend, Operand(dividend, ASR, shift));
   __ bind(&done);
 }
 
 
+void LCodeGen::DoFlooringDivByConstI(LFlooringDivByConstI* instr) {
+  Register dividend = ToRegister32(instr->dividend());
+  int32_t divisor = instr->divisor();
+  Register result = ToRegister32(instr->result());
+  ASSERT(!AreAliased(dividend, result));
+
+  if (divisor == 0) {
+    Deoptimize(instr->environment());
+    return;
+  }
+
+  // Check for (0 / -x) that will produce negative zero.
+  HMathFloorOfDiv* hdiv = instr->hydrogen();
+  if (hdiv->CheckFlag(HValue::kBailoutOnMinusZero) &&
+      hdiv->left()->RangeCanInclude(0) && divisor < 0) {
+    __ Cmp(dividend, 0);
+    DeoptimizeIf(eq, instr->environment());
+  }
+
+  __ FlooringDiv(result, dividend, divisor);
+}
+
+
 void LCodeGen::DoFlooringDivI(LFlooringDivI* instr) {
   Register dividend = ToRegister32(instr->dividend());
   Register divisor = ToRegister32(instr->divisor());
   Register remainder = ToRegister32(instr->temp());
   Register result = ToRegister32(instr->result());
 
   // This can't cause an exception on ARM, so we can speculatively
   // execute it already now.
   __ Sdiv(result, dividend, divisor);
 
@@ skipping 239 matching lines @@
     }
     __ B(&done);
   }
 
   __ bind(&dividend_is_not_negative);
   __ And(dividend, dividend, Operand(mask));
   __ bind(&done);
 }
 
 
+void LCodeGen::DoModByConstI(LModByConstI* instr) {
+  Register dividend = ToRegister32(instr->dividend());
+  int32_t divisor = instr->divisor();
+  Register result = ToRegister32(instr->result());
+  Register temp = ToRegister32(instr->temp());
+  ASSERT(!AreAliased(dividend, result, temp));
+
+  if (divisor == 0) {
+    Deoptimize(instr->environment());
+    return;
+  }
+
+  __ FlooringDiv(result, dividend, Abs(divisor));
+  __ Sxtw(dividend.X(), dividend);
+  __ Mov(temp, Abs(divisor));
+  __ Smsubl(result.X(), result, temp, dividend.X());
+
+  // Check for negative zero.
+  HMod* hmod = instr->hydrogen();
+  if (hmod->CheckFlag(HValue::kBailoutOnMinusZero) &&
+      hmod->left()->CanBeNegative()) {
+    Label remainder_not_zero;
+    __ Cbnz(result, &remainder_not_zero);
+    DeoptimizeIfNegative(dividend, instr->environment());
+    __ bind(&remainder_not_zero);
+  }
+}
+
+
 void LCodeGen::DoModI(LModI* instr) {
   Register dividend = ToRegister32(instr->left());
   Register divisor = ToRegister32(instr->right());
   Register result = ToRegister32(instr->result());
 
   Label deopt, done;
   // modulo = dividend - quotient * divisor
   __ Sdiv(result, dividend, divisor);
   if (instr->hydrogen()->right()->CanBeZero()) {
     // Combine the deoptimization sites.
@@ skipping 1620 matching lines @@
   __ Bind(&out_of_object);
   __ Ldr(result, FieldMemOperand(object, JSObject::kPropertiesOffset));
   // Index is equal to negated out of object property index plus 1.
   __ Sub(result, result, Operand::UntagSmiAndScale(index, kPointerSizeLog2));
   __ Ldr(result, FieldMemOperand(result,
                                  FixedArray::kHeaderSize - kPointerSize));
   __ Bind(&done);
 }
 
 } }  // namespace v8::internal