Speed up comparison with a constant.

Improve optimized code for comparison of an int32 against a constant, or comparison of two double constants.  Contributed by m.m.capewell.

Original codereview is http://codereview.chromium.org/7489045/.
This cl is just created in order to commit the change.

BUG=
TEST=

Review URL: http://codereview.chromium.org/8352040

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9718 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/lithium-arm.cc

@@ -1425,8 +1425,8 @@ LInstruction* LChunkBuilder::DoCompareIDAndBranch(
   if (r.IsInteger32()) {
     ASSERT(instr->left()->representation().IsInteger32());
     ASSERT(instr->right()->representation().IsInteger32());
-    LOperand* left = UseRegisterAtStart(instr->left());
-    LOperand* right = UseRegisterAtStart(instr->right());
+    LOperand* left = UseRegisterOrConstantAtStart(instr->left());
+    LOperand* right = UseRegisterOrConstantAtStart(instr->right());
     return new LCmpIDAndBranch(left, right);
   } else {
     ASSERT(r.IsDouble());

src/arm/lithium-codegen-arm.cc

@@ -410,6 +410,12 @@ int LCodeGen::ToInteger32(LConstantOperand* op) const {
 }
 
 
+double LCodeGen::ToDouble(LConstantOperand* op) const {
+  Handle<Object> value = chunk_->LookupLiteral(op);
+  return value->Number();
+}
+
+
 Operand LCodeGen::ToOperand(LOperand* op) {
   if (op->IsConstantOperand()) {
     LConstantOperand* const_op = LConstantOperand::cast(op);
@@ -1705,30 +1711,44 @@ Condition LCodeGen::TokenToCondition(Token::Value op, bool is_unsigned) {
 }
 
 
-void LCodeGen::EmitCmpI(LOperand* left, LOperand* right) {
-  __ cmp(ToRegister(left), ToRegister(right));
-}
-
-
 void LCodeGen::DoCmpIDAndBranch(LCmpIDAndBranch* instr) {
   LOperand* left = instr->InputAt(0);
   LOperand* right = instr->InputAt(1);
   int false_block = chunk_->LookupDestination(instr->false_block_id());
   int true_block = chunk_->LookupDestination(instr->true_block_id());
-
-  if (instr->is_double()) {
-    // Compare left and right as doubles and load the
-    // resulting flags into the normal status register.
-    __ VFPCompareAndSetFlags(ToDoubleRegister(left), ToDoubleRegister(right));
-    // If a NaN is involved, i.e. the result is unordered (V set),
-    // jump to false block label.
-    __ b(vs, chunk_->GetAssemblyLabel(false_block));
+  Condition cond = TokenToCondition(instr->op(), false);
+
+  if (left->IsConstantOperand() && right->IsConstantOperand()) {
+    // We can statically evaluate the comparison.
+    double left_val = ToDouble(LConstantOperand::cast(left));
+    double right_val = ToDouble(LConstantOperand::cast(right));
+    int next_block =
+      EvalComparison(instr->op(), left_val, right_val) ? true_block
+                                                       : false_block;
+    EmitGoto(next_block);
   } else {
-    EmitCmpI(left, right);
+    if (instr->is_double()) {
+      // Compare left and right operands as doubles and load the
+      // resulting flags into the normal status register.
+      __ VFPCompareAndSetFlags(ToDoubleRegister(left), ToDoubleRegister(right));
+      // If a NaN is involved, i.e. the result is unordered (V set),
+      // jump to false block label.
+      __ b(vs, chunk_->GetAssemblyLabel(false_block));
+    } else {
+      if (right->IsConstantOperand()) {
+        __ cmp(ToRegister(left),
+               Operand(ToInteger32(LConstantOperand::cast(right))));
+      } else if (left->IsConstantOperand()) {
+        __ cmp(ToRegister(right),
+               Operand(ToInteger32(LConstantOperand::cast(left))));
+        // We transposed the operands. Reverse the condition.
+        cond = ReverseCondition(cond);
+      } else {
+        __ cmp(ToRegister(left), ToRegister(right));
+      }
+    }
+    EmitBranch(true_block, false_block, cond);
   }
-
-  Condition cc = TokenToCondition(instr->op(), instr->is_double());
-  EmitBranch(true_block, false_block, cc);
 }
 
 

src/arm/lithium-codegen-arm.h

@@ -86,6 +86,7 @@ class LCodeGen BASE_EMBEDDED {
                                         SwVfpRegister flt_scratch,
                                         DoubleRegister dbl_scratch);
   int ToInteger32(LConstantOperand* op) const;
+  double ToDouble(LConstantOperand* op) const;
   Operand ToOperand(LOperand* op);
   MemOperand ToMemOperand(LOperand* op) const;
   // Returns a MemOperand pointing to the high word of a DoubleStackSlot.
@@ -263,7 +264,6 @@ class LCodeGen BASE_EMBEDDED {
   static Condition TokenToCondition(Token::Value op, bool is_unsigned);
   void EmitGoto(int block);
   void EmitBranch(int left_block, int right_block, Condition cc);
-  void EmitCmpI(LOperand* left, LOperand* right);
   void EmitNumberUntagD(Register input,
                         DoubleRegister result,
                         bool deoptimize_on_undefined,

src/assembler.cc

@@ -1137,6 +1137,23 @@ static int native_compare_doubles(double y, double x) {
 }
 
 
+bool EvalComparison(Token::Value op, double op1, double op2) {
+  ASSERT(Token::IsCompareOp(op));
+  switch (op) {
+    case Token::EQ:
+    case Token::EQ_STRICT: return (op1 == op2);
+    case Token::NE: return (op1 != op2);
+    case Token::LT: return (op1 < op2);
+    case Token::GT: return (op1 > op2);
+    case Token::LTE: return (op1 <= op2);
+    case Token::GTE: return (op1 >= op2);
+    default:
+      UNREACHABLE();
+      return false;
+  }
+}
+
+
 ExternalReference ExternalReference::double_fp_operation(
     Token::Value operation, Isolate* isolate) {
   typedef double BinaryFPOperation(double x, double y);

src/assembler.h

@@ -847,6 +847,8 @@ static inline int NumberOfBitsSet(uint32_t x) {
   return num_bits_set;
 }
 
+bool EvalComparison(Token::Value op, double op1, double op2);
+
 // Computes pow(x, y) with the special cases in the spec for Math.pow.
 double power_double_int(double x, int y);
 double power_double_double(double x, double y);

src/ia32/lithium-codegen-ia32.cc

@@ -355,6 +355,12 @@ int LCodeGen::ToInteger32(LConstantOperand* op) const {
 }
 
 
+double LCodeGen::ToDouble(LConstantOperand* op) const {
+  Handle<Object> value = chunk_->LookupLiteral(op);
+  return value->Number();
+}
+
+
 Immediate LCodeGen::ToImmediate(LOperand* op) {
   LConstantOperand* const_op = LConstantOperand::cast(op);
   Handle<Object> literal = chunk_->LookupLiteral(const_op);
@@ -1574,32 +1580,40 @@ Condition LCodeGen::TokenToCondition(Token::Value op, bool is_unsigned) {
 }
 
 
-void LCodeGen::EmitCmpI(LOperand* left, LOperand* right) {
-  if (right->IsConstantOperand()) {
-    __ cmp(ToOperand(left), ToImmediate(right));
-  } else {
-    __ cmp(ToRegister(left), ToOperand(right));
-  }
-}
-
-
 void LCodeGen::DoCmpIDAndBranch(LCmpIDAndBranch* instr) {
   LOperand* left = instr->InputAt(0);
   LOperand* right = instr->InputAt(1);
   int false_block = chunk_->LookupDestination(instr->false_block_id());
   int true_block = chunk_->LookupDestination(instr->true_block_id());
+  Condition cc = TokenToCondition(instr->op(), instr->is_double());
 
-  if (instr->is_double()) {
-    // Don't base result on EFLAGS when a NaN is involved. Instead
-    // jump to the false block.
-    __ ucomisd(ToDoubleRegister(left), ToDoubleRegister(right));
-    __ j(parity_even, chunk_->GetAssemblyLabel(false_block));
+  if (left->IsConstantOperand() && right->IsConstantOperand()) {
+    // We can statically evaluate the comparison.
+    double left_val = ToDouble(LConstantOperand::cast(left));
+    double right_val = ToDouble(LConstantOperand::cast(right));
+    int next_block =
+      EvalComparison(instr->op(), left_val, right_val) ? true_block
+                                                       : false_block;
+    EmitGoto(next_block);
   } else {
-    EmitCmpI(left, right);
+    if (instr->is_double()) {
+      // Don't base result on EFLAGS when a NaN is involved. Instead
+      // jump to the false block.
+      __ ucomisd(ToDoubleRegister(left), ToDoubleRegister(right));
+      __ j(parity_even, chunk_->GetAssemblyLabel(false_block));
+    } else {
+      if (right->IsConstantOperand()) {
+        __ cmp(ToRegister(left), ToImmediate(right));
+      } else if (left->IsConstantOperand()) {
+        __ cmp(ToOperand(right), ToImmediate(left));
+        // We transposed the operands. Reverse the condition.
+        cc = ReverseCondition(cc);
+      } else {
+        __ cmp(ToRegister(left), ToOperand(right));
+      }
+    }
+    EmitBranch(true_block, false_block, cc);
   }
-
-  Condition cc = TokenToCondition(instr->op(), instr->is_double());
-  EmitBranch(true_block, false_block, cc);
 }
 
 

src/ia32/lithium-codegen-ia32.h

@@ -227,6 +227,7 @@ class LCodeGen BASE_EMBEDDED {
   Register ToRegister(int index) const;
   XMMRegister ToDoubleRegister(int index) const;
   int ToInteger32(LConstantOperand* op) const;
+  double ToDouble(LConstantOperand* op) const;
   Operand BuildFastArrayOperand(LOperand* elements_pointer,
                                 LOperand* key,
                                 ElementsKind elements_kind,
@@ -261,7 +262,6 @@ class LCodeGen BASE_EMBEDDED {
   static Condition TokenToCondition(Token::Value op, bool is_unsigned);
   void EmitGoto(int block);
   void EmitBranch(int left_block, int right_block, Condition cc);
-  void EmitCmpI(LOperand* left, LOperand* right);
   void EmitNumberUntagD(Register input,
                         XMMRegister result,
                         bool deoptimize_on_undefined,

src/ia32/lithium-ia32.cc

@@ -1456,15 +1456,22 @@ LInstruction* LChunkBuilder::DoCompareIDAndBranch(
   if (r.IsInteger32()) {
     ASSERT(instr->left()->representation().IsInteger32());
     ASSERT(instr->right()->representation().IsInteger32());
-    LOperand* left = UseRegisterAtStart(instr->left());
+    LOperand* left = UseRegisterOrConstantAtStart(instr->left());
     LOperand* right = UseOrConstantAtStart(instr->right());
     return new LCmpIDAndBranch(left, right);
   } else {
     ASSERT(r.IsDouble());
     ASSERT(instr->left()->representation().IsDouble());
     ASSERT(instr->right()->representation().IsDouble());
-    LOperand* left = UseRegisterAtStart(instr->left());
-    LOperand* right = UseRegisterAtStart(instr->right());
+    LOperand* left;
+    LOperand* right;
+    if (instr->left()->IsConstant() && instr->right()->IsConstant()) {
+      left = UseRegisterOrConstantAtStart(instr->left());
+      right = UseRegisterOrConstantAtStart(instr->right());
+    } else {
+      left = UseRegisterAtStart(instr->left());
+      right = UseRegisterAtStart(instr->right());
+    }
     return new LCmpIDAndBranch(left, right);
   }
 }

src/x64/lithium-codegen-x64.cc

@@ -374,6 +374,12 @@ int LCodeGen::ToInteger32(LConstantOperand* op) const {
 }
 
 
+double LCodeGen::ToDouble(LConstantOperand* op) const {
+  Handle<Object> value = chunk_->LookupLiteral(op);
+  return value->Number();
+}
+
+
 Handle<Object> LCodeGen::ToHandle(LConstantOperand* op) const {
   Handle<Object> literal = chunk_->LookupLiteral(op);
   ASSERT(chunk_->LookupLiteralRepresentation(op).IsTagged());
@@ -1526,39 +1532,51 @@ inline Condition LCodeGen::TokenToCondition(Token::Value op, bool is_unsigned) {
 }
 
 
-void LCodeGen::EmitCmpI(LOperand* left, LOperand* right) {
-  if (right->IsConstantOperand()) {
-    int32_t value = ToInteger32(LConstantOperand::cast(right));
-    if (left->IsRegister()) {
-      __ cmpl(ToRegister(left), Immediate(value));
-    } else {
-      __ cmpl(ToOperand(left), Immediate(value));
-    }
-  } else if (right->IsRegister()) {
-    __ cmpl(ToRegister(left), ToRegister(right));
-  } else {
-    __ cmpl(ToRegister(left), ToOperand(right));
-  }
-}
-
-
 void LCodeGen::DoCmpIDAndBranch(LCmpIDAndBranch* instr) {
   LOperand* left = instr->InputAt(0);
   LOperand* right = instr->InputAt(1);
   int false_block = chunk_->LookupDestination(instr->false_block_id());
   int true_block = chunk_->LookupDestination(instr->true_block_id());
+  Condition cc = TokenToCondition(instr->op(), instr->is_double());
 
-  if (instr->is_double()) {
-    // Don't base result on EFLAGS when a NaN is involved. Instead
-    // jump to the false block.
-    __ ucomisd(ToDoubleRegister(left), ToDoubleRegister(right));
-    __ j(parity_even, chunk_->GetAssemblyLabel(false_block));
+  if (left->IsConstantOperand() && right->IsConstantOperand()) {
+    // We can statically evaluate the comparison.
+    double left_val = ToDouble(LConstantOperand::cast(left));
+    double right_val = ToDouble(LConstantOperand::cast(right));
+    int next_block =
+      EvalComparison(instr->op(), left_val, right_val) ? true_block
+                                                       : false_block;
+    EmitGoto(next_block);
   } else {
-    EmitCmpI(left, right);
+    if (instr->is_double()) {
+      // Don't base result on EFLAGS when a NaN is involved. Instead
+      // jump to the false block.
+      __ ucomisd(ToDoubleRegister(left), ToDoubleRegister(right));
+      __ j(parity_even, chunk_->GetAssemblyLabel(false_block));
+    } else {
+      int32_t value;
+      if (right->IsConstantOperand()) {
+        value = ToInteger32(LConstantOperand::cast(right));
+        __ cmpl(ToRegister(left), Immediate(value));
+      } else if (left->IsConstantOperand()) {
+        value = ToInteger32(LConstantOperand::cast(left));
+        if (right->IsRegister()) {
+          __ cmpl(ToRegister(right), Immediate(value));
+        } else {
+          __ cmpl(ToOperand(right), Immediate(value));
+        }
+        // We transposed the operands. Reverse the condition.
+        cc = ReverseCondition(cc);
+      } else {
+        if (right->IsRegister()) {
+          __ cmpl(ToRegister(left), ToRegister(right));
+        } else {
+          __ cmpl(ToRegister(left), ToOperand(right));
+        }
+      }
+    }
+    EmitBranch(true_block, false_block, cc);
   }
-
-  Condition cc = TokenToCondition(instr->op(), instr->is_double());
-  EmitBranch(true_block, false_block, cc);
 }
 
 

src/x64/lithium-codegen-x64.h

@@ -77,6 +77,7 @@ class LCodeGen BASE_EMBEDDED {
   XMMRegister ToDoubleRegister(LOperand* op) const;
   bool IsInteger32Constant(LConstantOperand* op) const;
   int ToInteger32(LConstantOperand* op) const;
+  double ToDouble(LConstantOperand* op) const;
   bool IsTaggedConstant(LConstantOperand* op) const;
   Handle<Object> ToHandle(LConstantOperand* op) const;
   Operand ToOperand(LOperand* op) const;
@@ -250,7 +251,6 @@ class LCodeGen BASE_EMBEDDED {
   static Condition TokenToCondition(Token::Value op, bool is_unsigned);
   void EmitGoto(int block);
   void EmitBranch(int left_block, int right_block, Condition cc);
-  void EmitCmpI(LOperand* left, LOperand* right);
   void EmitNumberUntagD(Register input,
                         XMMRegister result,
                         bool deoptimize_on_undefined,

src/x64/lithium-x64.cc

@@ -1417,15 +1417,22 @@ LInstruction* LChunkBuilder::DoCompareIDAndBranch(
   if (r.IsInteger32()) {
     ASSERT(instr->left()->representation().IsInteger32());
     ASSERT(instr->right()->representation().IsInteger32());
-    LOperand* left = UseRegisterAtStart(instr->left());
+    LOperand* left = UseRegisterOrConstantAtStart(instr->left());
     LOperand* right = UseOrConstantAtStart(instr->right());
     return new LCmpIDAndBranch(left, right);
   } else {
     ASSERT(r.IsDouble());
     ASSERT(instr->left()->representation().IsDouble());
     ASSERT(instr->right()->representation().IsDouble());
-    LOperand* left = UseRegisterAtStart(instr->left());
-    LOperand* right = UseRegisterAtStart(instr->right());
+    LOperand* left;
+    LOperand* right;
+    if (instr->left()->IsConstant() && instr->right()->IsConstant()) {
+      left = UseRegisterOrConstantAtStart(instr->left());
+      right = UseRegisterOrConstantAtStart(instr->right());
+    } else {
+      left = UseRegisterAtStart(instr->left());
+      right = UseRegisterAtStart(instr->right());
+    }
     return new LCmpIDAndBranch(left, right);
   }
 }