Consistenly handle power-of-2 divisors in division-like operations

src/a64/lithium-a64.cc

Index: src/a64/lithium-a64.cc
diff --git a/src/a64/lithium-a64.cc b/src/a64/lithium-a64.cc
index ae8705de436a5fc08b1f164695b6febecdc267c0..d2025fcb9a2ffb3d628a05b4f4c9a1a20ea3c0cb 100644
--- a/src/a64/lithium-a64.cc
+++ b/src/a64/lithium-a64.cc
@@ -1368,23 +1368,44 @@ LInstruction* LChunkBuilder::DoDeoptimize(HDeoptimize* instr) {
 }
 
 
+LInstruction* LChunkBuilder::DoDivByPowerOf2I(HDiv* instr) {
+  ASSERT(instr->representation().IsSmiOrInteger32());
+  ASSERT(instr->left()->representation().Equals(instr->representation()));
+  ASSERT(instr->right()->representation().Equals(instr->representation()));
+  LOperand* dividend = UseRegister(instr->left());
+  int32_t divisor = instr->right()->GetInteger32Constant();
+  LInstruction* result =
+      DefineAsRegister(new(zone()) LDivByPowerOf2I(dividend, divisor));
+  bool can_deopt =
+      (instr->CheckFlag(HValue::kBailoutOnMinusZero) &&
+       instr->left()->RangeCanInclude(0) && divisor < 0) ||
+      (instr->CheckFlag(HValue::kCanOverflow) &&
+       instr->left()->RangeCanInclude(kMinInt) && divisor == -1) ||
+      (!instr->CheckFlag(HInstruction::kAllUsesTruncatingToInt32) &&
+       divisor != 1 && divisor != -1);
+  return can_deopt ? AssignEnvironment(result) : result;
+}
+
+
+LInstruction* LChunkBuilder::DoDivI(HBinaryOperation* instr) {
+  ASSERT(instr->representation().IsSmiOrInteger32());
+  ASSERT(instr->left()->representation().Equals(instr->representation()));
+  ASSERT(instr->right()->representation().Equals(instr->representation()));
+  LOperand* dividend = UseRegister(instr->left());
+  LOperand* divisor = UseRegister(instr->right());
+  LOperand* temp = instr->CheckFlag(HInstruction::kAllUsesTruncatingToInt32)
+      ? NULL : TempRegister();
+  LDivI* div = new(zone()) LDivI(dividend, divisor, temp);
+  return AssignEnvironment(DefineAsRegister(div));
+}
+
+
 LInstruction* LChunkBuilder::DoDiv(HDiv* instr) {
-  if (instr->representation().IsInteger32()) {
-    // TODO(all): Update this case to support smi inputs.
-    ASSERT(instr->left()->representation().Equals(instr->representation()));
-    ASSERT(instr->right()->representation().Equals(instr->representation()));
-    if (instr->RightIsPowerOf2()) {
-      ASSERT(!instr->CheckFlag(HValue::kCanBeDivByZero));
-      LOperand* value = UseRegister(instr->left());
-      LDivI* div = new(zone()) LDivI(value, UseConstant(instr->right()), NULL);
-      return AssignEnvironment(DefineAsRegister(div));
-    }
-    LOperand* dividend = UseRegister(instr->left());
-    LOperand* divisor = UseRegister(instr->right());
-    LOperand* temp = instr->CheckFlag(HInstruction::kAllUsesTruncatingToInt32)
-        ? NULL : TempRegister();
-    LDivI* div = new(zone()) LDivI(dividend, divisor, temp);
-    return AssignEnvironment(DefineAsRegister(div));
+  if (instr->representation().IsSmiOrInteger32()) {
+    // TODO(all): Add Smi support to DoDivI and turn this into a ternary.
+    if (instr->RightIsPowerOf2()) return DoDivByPowerOf2I(instr);
+    if (instr->representation().IsInteger32()) return DoDivI(instr);
+    return DoArithmeticT(Token::DIV, instr);
   } else if (instr->representation().IsDouble()) {
     return DoArithmeticD(Token::DIV, instr);
   } else {
@@ -1692,13 +1713,37 @@ LInstruction* LChunkBuilder::DoMapEnumLength(HMapEnumLength* instr) {
 }
 
 
-LInstruction* LChunkBuilder::DoMathFloorOfDiv(HMathFloorOfDiv* instr) {
-  HValue* right = instr->right();
+LInstruction* LChunkBuilder::DoFlooringDivByPowerOf2I(HMathFloorOfDiv* instr) {
+  LOperand* dividend = UseRegisterAtStart(instr->left());
+  int32_t divisor = instr->right()->GetInteger32Constant();
+  LInstruction* result =
+      DefineSameAsFirst(new(zone()) LFlooringDivByPowerOf2I(dividend, divisor));
+  bool can_deopt =
+      (instr->CheckFlag(HValue::kBailoutOnMinusZero) && divisor < 0) ||
+      (instr->left()->RangeCanInclude(kMinInt) && divisor == -1);
+  return can_deopt ? AssignEnvironment(result) : result;
+}
+
+
+LInstruction* LChunkBuilder::DoFlooringDivI(HMathFloorOfDiv* instr) {
   LOperand* dividend = UseRegister(instr->left());
-  LOperand* divisor = UseRegister(right);
+  LOperand* divisor = UseRegister(instr->right());
   LOperand* remainder = TempRegister();
-  return AssignEnvironment(DefineAsRegister(
-          new(zone()) LMathFloorOfDiv(dividend, divisor, remainder)));
+  LInstruction* result =
+      DefineAsRegister(new(zone()) LFlooringDivI(dividend, divisor, remainder));
+  return AssignEnvironment(result);
+}
+
+
+LInstruction* LChunkBuilder::DoMathFloorOfDiv(HMathFloorOfDiv* instr) {
+  if (instr->RightIsPowerOf2()) {
+    return DoFlooringDivByPowerOf2I(instr);
+  } else if (instr->right()->IsConstant()) {
+    // TODO(svenpanne) Do something more efficient in this case.
+    return DoFlooringDivI(instr);
+  } else {
+    return DoFlooringDivI(instr);
+  }
 }
 
 
@@ -1721,38 +1766,46 @@ LInstruction* LChunkBuilder::DoMathMinMax(HMathMinMax* instr) {
 }
 
 
-LInstruction* LChunkBuilder::DoMod(HMod* hmod) {
-  HValue* hleft = hmod->left();
-  HValue* hright = hmod->right();
-
-  // TODO(jbramley): Add smi support.
-  if (hmod->representation().IsInteger32()) {
-    ASSERT(hleft->representation().IsInteger32());
-    ASSERT(hleft->representation().IsInteger32());
-    LOperand* left_op;
-    LOperand* right_op;
+LInstruction* LChunkBuilder::DoModByPowerOf2I(HMod* instr) {
+  ASSERT(instr->representation().IsSmiOrInteger32());
+  ASSERT(instr->left()->representation().Equals(instr->representation()));
+  ASSERT(instr->right()->representation().Equals(instr->representation()));
+  LOperand* dividend = UseRegisterAtStart(instr->left());
+  int32_t divisor = instr->right()->GetInteger32Constant();
+  LInstruction* result =
+      DefineSameAsFirst(new(zone()) LModByPowerOf2I(dividend, divisor));
+  bool can_deopt =
+      instr->CheckFlag(HValue::kBailoutOnMinusZero) &&
+      instr->left()->CanBeNegative();
+  return can_deopt ? AssignEnvironment(result) : result;
+}
 
-    if (hmod->RightIsPowerOf2()) {
-      left_op = UseRegisterAtStart(hleft);
-      right_op = UseConstant(hright);
-    } else {
-      right_op = UseRegister(hright);
-      left_op = UseRegister(hleft);
-    }
 
-    LModI* lmod = new(zone()) LModI(left_op, right_op);
+LInstruction* LChunkBuilder::DoModI(HMod* instr) {
+  ASSERT(instr->representation().IsSmiOrInteger32());
+  ASSERT(instr->left()->representation().Equals(instr->representation()));
+  ASSERT(instr->right()->representation().Equals(instr->representation()));
+  LOperand* dividend = UseRegister(instr->left());
+  LOperand* divisor = UseRegister(instr->right());
+  LInstruction* result =
+      DefineAsRegister(new(zone()) LModI(dividend, divisor));
+  bool can_deopt = (instr->right()->CanBeZero() ||
+                    (instr->CheckFlag(HValue::kBailoutOnMinusZero) &&
+                     instr->left()->CanBeNegative() && instr->CanBeZero()));
+  return can_deopt ? AssignEnvironment(result) : result;
+}
 
-    if (hmod->right()->CanBeZero() ||
-        (hmod->CheckFlag(HValue::kBailoutOnMinusZero) &&
-         hmod->left()->CanBeNegative() && hmod->CanBeZero())) {
-      AssignEnvironment(lmod);
-    }
-    return DefineAsRegister(lmod);
 
-  } else if (hmod->representation().IsSmiOrTagged()) {
-    return DoArithmeticT(Token::MOD, hmod);
+LInstruction* LChunkBuilder::DoMod(HMod* instr) {
+  if (instr->representation().IsSmiOrInteger32()) {
+    // TODO(all): Add Smi support to DoDivI and turn this into a ternary.
+    if (instr->RightIsPowerOf2()) return DoModByPowerOf2I(instr);
+    if (instr->representation().IsInteger32()) return DoModI(instr);
+    return DoArithmeticT(Token::MOD, instr);
+  } else if (instr->representation().IsDouble()) {
+    return DoArithmeticD(Token::MOD, instr);
   } else {
-    return DoArithmeticD(Token::MOD, hmod);
+    return DoArithmeticT(Token::MOD, instr);
   }
 }