[turbofan] Improve code generation for inline comparisons with zero.

src/compiler/arm/instruction-selector-arm.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/base/bits.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 882 matching lines @@
     DCHECK(cont->IsSet());
     selector->Emit(
         cont->Encode(kArmVcmpF64), g.DefineAsRegister(cont->result()),
         g.UseRegister(m.left().node()), g.UseRegister(m.right().node()));
   }
 }
 
 
 // Shared routine for multiple word compare operations.
 void VisitWordCompare(InstructionSelector* selector, Node* node,
-                      InstructionCode opcode, FlagsContinuation* cont,
-                      bool commutative) {
+                      InstructionCode opcode, FlagsContinuation* cont) {
   ArmOperandGenerator g(selector);
   Int32BinopMatcher m(node);
   InstructionOperand* inputs[5];
   size_t input_count = 0;
   InstructionOperand* outputs[1];
   size_t output_count = 0;
 
   if (TryMatchImmediateOrShift(selector, &opcode, m.right().node(),
                                &input_count, &inputs[1])) {
     inputs[0] = g.UseRegister(m.left().node());
     input_count++;
   } else if (TryMatchImmediateOrShift(selector, &opcode, m.left().node(),
                                       &input_count, &inputs[1])) {
-    if (!commutative) cont->Commute();
+    if (!node->op()->HasProperty(Operator::kCommutative)) cont->Commute();
     inputs[0] = g.UseRegister(m.right().node());
     input_count++;
   } else {
     opcode |= AddressingModeField::encode(kMode_Operand2_R);
     inputs[input_count++] = g.UseRegister(m.left().node());
     inputs[input_count++] = g.UseRegister(m.right().node());
   }
 
   if (cont->IsBranch()) {
     inputs[input_count++] = g.Label(cont->true_block());
     inputs[input_count++] = g.Label(cont->false_block());
   } else {
     DCHECK(cont->IsSet());
     outputs[output_count++] = g.DefineAsRegister(cont->result());
   }
 
   DCHECK_NE(0, input_count);
   DCHECK_GE(arraysize(inputs), input_count);
   DCHECK_GE(arraysize(outputs), output_count);
 
   Instruction* instr = selector->Emit(cont->Encode(opcode), output_count,
                                       outputs, input_count, inputs);
   if (cont->IsBranch()) instr->MarkAsControl();
 }
 
 
 void VisitWordCompare(InstructionSelector* selector, Node* node,
                       FlagsContinuation* cont) {
-  VisitWordCompare(selector, node, kArmCmp, cont, false);
+  VisitWordCompare(selector, node, kArmCmp, cont);
 }
 
 
-void VisitWordTest(InstructionSelector* selector, Node* node,
-                   FlagsContinuation* cont) {
-  ArmOperandGenerator g(selector);
-  InstructionCode opcode =
-      cont->Encode(kArmTst) | AddressingModeField::encode(kMode_Operand2_R);
-  if (cont->IsBranch()) {
-    selector->Emit(opcode, nullptr, g.UseRegister(node), g.UseRegister(node),
-                   g.Label(cont->true_block()),
-                   g.Label(cont->false_block()))->MarkAsControl();
-  } else {
-    selector->Emit(opcode, g.DefineAsRegister(cont->result()),
-                   g.UseRegister(node), g.UseRegister(node));
-  }
-}
-
-}  // namespace
-
-
-void InstructionSelector::VisitBranch(Node* branch, BasicBlock* tbranch,
-                                      BasicBlock* fbranch) {
-  ArmOperandGenerator g(this);
-  Node* user = branch;
-  Node* value = branch->InputAt(0);
-
-  FlagsContinuation cont(kNotEqual, tbranch, fbranch);
-
-  // If we can fall through to the true block, invert the branch.
-  if (IsNextInAssemblyOrder(tbranch)) {
-    cont.Negate();
-    cont.SwapBlocks();
-  }
-
-  // Try to combine with comparisons against 0 by simply inverting the branch.
-  while (CanCover(user, value) && value->opcode() == IrOpcode::kWord32Equal) {
-    Int32BinopMatcher m(value);
-    if (m.right().Is(0)) {
-      user = value;
-      value = m.left().node();
-      cont.Negate();
-    } else {
-      break;
-    }
-  }
-
-  // Try to combine the branch with a comparison.
-  if (CanCover(user, value)) {
+// Shared routine for word comparisons against zero.
+void VisitWordCompareZero(InstructionSelector* selector, Node* user,
+                          Node* value, FlagsContinuation* cont) {
+  while (selector->CanCover(user, value)) {
     switch (value->opcode()) {
-      case IrOpcode::kWord32Equal:
-        cont.OverwriteAndNegateIfEqual(kEqual);
-        return VisitWordCompare(this, value, &cont);
+      case IrOpcode::kWord32Equal: {
+        // Combine with comparisons against 0 by simply inverting the
+        // continuation.
+        Int32BinopMatcher m(value);
+        if (m.right().Is(0)) {
+          user = value;
+          value = m.left().node();
+          cont->Negate();
+          continue;
+        }
+        cont->OverwriteAndNegateIfEqual(kEqual);
+        return VisitWordCompare(selector, value, cont);
+      }
       case IrOpcode::kInt32LessThan:
-        cont.OverwriteAndNegateIfEqual(kSignedLessThan);
-        return VisitWordCompare(this, value, &cont);
+        cont->OverwriteAndNegateIfEqual(kSignedLessThan);
+        return VisitWordCompare(selector, value, cont);
       case IrOpcode::kInt32LessThanOrEqual:
-        cont.OverwriteAndNegateIfEqual(kSignedLessThanOrEqual);
-        return VisitWordCompare(this, value, &cont);
+        cont->OverwriteAndNegateIfEqual(kSignedLessThanOrEqual);
+        return VisitWordCompare(selector, value, cont);
       case IrOpcode::kUint32LessThan:
-        cont.OverwriteAndNegateIfEqual(kUnsignedLessThan);
-        return VisitWordCompare(this, value, &cont);
+        cont->OverwriteAndNegateIfEqual(kUnsignedLessThan);
+        return VisitWordCompare(selector, value, cont);
       case IrOpcode::kUint32LessThanOrEqual:
-        cont.OverwriteAndNegateIfEqual(kUnsignedLessThanOrEqual);
-        return VisitWordCompare(this, value, &cont);
+        cont->OverwriteAndNegateIfEqual(kUnsignedLessThanOrEqual);
+        return VisitWordCompare(selector, value, cont);
       case IrOpcode::kFloat64Equal:
-        cont.OverwriteAndNegateIfEqual(kUnorderedEqual);
-        return VisitFloat64Compare(this, value, &cont);
+        cont->OverwriteAndNegateIfEqual(kUnorderedEqual);
+        return VisitFloat64Compare(selector, value, cont);
       case IrOpcode::kFloat64LessThan:
-        cont.OverwriteAndNegateIfEqual(kUnorderedLessThan);
-        return VisitFloat64Compare(this, value, &cont);
+        cont->OverwriteAndNegateIfEqual(kUnorderedLessThan);
+        return VisitFloat64Compare(selector, value, cont);
       case IrOpcode::kFloat64LessThanOrEqual:
-        cont.OverwriteAndNegateIfEqual(kUnorderedLessThanOrEqual);
-        return VisitFloat64Compare(this, value, &cont);
+        cont->OverwriteAndNegateIfEqual(kUnorderedLessThanOrEqual);
+        return VisitFloat64Compare(selector, value, cont);
       case IrOpcode::kProjection:
         // Check if this is the overflow output projection of an
         // <Operation>WithOverflow node.
         if (OpParameter<size_t>(value) == 1u) {
           // We cannot combine the <Operation>WithOverflow with this branch
           // unless the 0th projection (the use of the actual value of the
           // <Operation> is either NULL, which means there's no use of the
           // actual value, or was already defined, which means it is scheduled
           // *AFTER* this branch).
-          Node* node = value->InputAt(0);
-          Node* result = node->FindProjection(0);
-          if (!result || IsDefined(result)) {
+          Node* const node = value->InputAt(0);
+          Node* const result = node->FindProjection(0);
+          if (!result || selector->IsDefined(result)) {
             switch (node->opcode()) {
               case IrOpcode::kInt32AddWithOverflow:
-                cont.OverwriteAndNegateIfEqual(kOverflow);
-                return VisitBinop(this, node, kArmAdd, kArmAdd, &cont);
+                cont->OverwriteAndNegateIfEqual(kOverflow);
+                return VisitBinop(selector, node, kArmAdd, kArmAdd, cont);
               case IrOpcode::kInt32SubWithOverflow:
-                cont.OverwriteAndNegateIfEqual(kOverflow);
-                return VisitBinop(this, node, kArmSub, kArmRsb, &cont);
+                cont->OverwriteAndNegateIfEqual(kOverflow);
+                return VisitBinop(selector, node, kArmSub, kArmRsb, cont);
               default:
                 break;
             }
           }
         }
         break;
       case IrOpcode::kInt32Add:
-        return VisitWordCompare(this, value, kArmCmn, &cont, true);
+        return VisitWordCompare(selector, value, kArmCmn, cont);
       case IrOpcode::kInt32Sub:
-        return VisitWordCompare(this, value, kArmCmp, &cont, false);
+        return VisitWordCompare(selector, value, kArmCmp, cont);
       case IrOpcode::kWord32And:
-        return VisitWordCompare(this, value, kArmTst, &cont, true);
+        return VisitWordCompare(selector, value, kArmTst, cont);
       case IrOpcode::kWord32Or:
-        return VisitBinop(this, value, kArmOrr, kArmOrr, &cont);
+        return VisitBinop(selector, value, kArmOrr, kArmOrr, cont);
       case IrOpcode::kWord32Xor:
-        return VisitWordCompare(this, value, kArmTeq, &cont, true);
+        return VisitWordCompare(selector, value, kArmTeq, cont);
       case IrOpcode::kWord32Sar:
-        return VisitShift(this, value, TryMatchASR, &cont);
+        return VisitShift(selector, value, TryMatchASR, cont);
       case IrOpcode::kWord32Shl:
-        return VisitShift(this, value, TryMatchLSL, &cont);
+        return VisitShift(selector, value, TryMatchLSL, cont);
       case IrOpcode::kWord32Shr:
-        return VisitShift(this, value, TryMatchLSR, &cont);
+        return VisitShift(selector, value, TryMatchLSR, cont);
       case IrOpcode::kWord32Ror:
-        return VisitShift(this, value, TryMatchROR, &cont);
+        return VisitShift(selector, value, TryMatchROR, cont);
       default:
         break;
     }
+    break;
   }
 
-  // Branch could not be combined with a compare, emit compare against 0.
-  return VisitWordTest(this, value, &cont);
+  // Continuation could not be combined with a compare, emit compare against 0.
+  ArmOperandGenerator g(selector);
+  InstructionCode const opcode =
+      cont->Encode(kArmTst) | AddressingModeField::encode(kMode_Operand2_R);
+  InstructionOperand* const value_operand = g.UseRegister(value);
+  if (cont->IsBranch()) {
+    selector->Emit(opcode, nullptr, value_operand, value_operand,
+                   g.Label(cont->true_block()),
+                   g.Label(cont->false_block()))->MarkAsControl();
+  } else {
+    selector->Emit(opcode, g.DefineAsRegister(cont->result()), value_operand,
+                   value_operand);
+  }
+}
+
+}  // namespace
+
+
+void InstructionSelector::VisitBranch(Node* branch, BasicBlock* tbranch,
+                                      BasicBlock* fbranch) {
+  FlagsContinuation cont(kNotEqual, tbranch, fbranch);
+  if (IsNextInAssemblyOrder(tbranch)) {  // We can fallthru to the true block.
+    cont.Negate();
+    cont.SwapBlocks();
+  }
+  VisitWordCompareZero(this, branch, branch->InputAt(0), &cont);
 }
 
 
 void InstructionSelector::VisitWord32Equal(Node* const node) {
-  Node* const user = node;
   FlagsContinuation cont(kEqual, node);
-  Int32BinopMatcher m(user);
+  Int32BinopMatcher m(node);
   if (m.right().Is(0)) {
-    Node* const value = m.left().node();
-    if (CanCover(user, value)) {
-      switch (value->opcode()) {
-        case IrOpcode::kInt32Add:
-          return VisitWordCompare(this, value, kArmCmn, &cont, true);
-        case IrOpcode::kInt32Sub:
-          return VisitWordCompare(this, value, kArmCmp, &cont, false);
-        case IrOpcode::kWord32And:
-          return VisitWordCompare(this, value, kArmTst, &cont, true);
-        case IrOpcode::kWord32Or:
-          return VisitBinop(this, value, kArmOrr, kArmOrr, &cont);
-        case IrOpcode::kWord32Xor:
-          return VisitWordCompare(this, value, kArmTeq, &cont, true);
-        case IrOpcode::kWord32Sar:
-          return VisitShift(this, value, TryMatchASR, &cont);
-        case IrOpcode::kWord32Shl:
-          return VisitShift(this, value, TryMatchLSL, &cont);
-        case IrOpcode::kWord32Shr:
-          return VisitShift(this, value, TryMatchLSR, &cont);
-        case IrOpcode::kWord32Ror:
-          return VisitShift(this, value, TryMatchROR, &cont);
-        default:
-          break;
-      }
-      return VisitWordTest(this, value, &cont);
-    }
+    return VisitWordCompareZero(this, m.node(), m.left().node(), &cont);
   }
   VisitWordCompare(this, node, &cont);
 }
 
 
 void InstructionSelector::VisitInt32LessThan(Node* node) {
   FlagsContinuation cont(kSignedLessThan, node);
   VisitWordCompare(this, node, &cont);
 }
 
@@ skipping 49 matching lines @@
 
 
 void InstructionSelector::VisitFloat64LessThanOrEqual(Node* node) {
   FlagsContinuation cont(kUnorderedLessThanOrEqual, node);
   VisitFloat64Compare(this, node, &cont);
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8