[turbofan] Refactor the compare-zero folding in instruction selector.

src/compiler/mips64/instruction-selector-mips64.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/adapters.h"
 #include "src/base/bits.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
@@ skipping 2019 matching lines @@
   } else {
     selector->Emit(opcode, g.DefineAsRegister(cont->result()), value_operand,
                    g.TempImmediate(0));
   }
 }
 
 
 // Shared routine for word comparisons against zero.
 void VisitWordCompareZero(InstructionSelector* selector, Node* user,
                           Node* value, FlagsContinuation* cont) {
+  // Try to combine with comparisons against 0 by simply inverting the branch.
   while (selector->CanCover(user, value)) {
+    if (value->opcode() == IrOpcode::kWord32Equal) {
+      Int32BinopMatcher m(value);
+      if (!m.right().Is(0)) break;
+      user = value;
+      value = m.left().node();
+    } else if (value->opcode() == IrOpcode::kWord64Equal) {
+      Int64BinopMatcher m(value);
+      if (!m.right().Is(0)) break;
+      user = value;
+      value = m.left().node();
+    } else {
+      break;
+    }
+
+    cont->Negate();
+  }
+
+  if (selector->CanCover(user, value)) {
     switch (value->opcode()) {
-      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;
-        }
+      case IrOpcode::kWord32Equal:
         cont->OverwriteAndNegateIfEqual(kEqual);
         return VisitWord32Compare(selector, value, cont);
-      }
       case IrOpcode::kInt32LessThan:
         cont->OverwriteAndNegateIfEqual(kSignedLessThan);
         return VisitWord32Compare(selector, value, cont);
       case IrOpcode::kInt32LessThanOrEqual:
         cont->OverwriteAndNegateIfEqual(kSignedLessThanOrEqual);
         return VisitWord32Compare(selector, value, cont);
       case IrOpcode::kUint32LessThan:
         cont->OverwriteAndNegateIfEqual(kUnsignedLessThan);
         return VisitWord32Compare(selector, value, cont);
       case IrOpcode::kUint32LessThanOrEqual:
         cont->OverwriteAndNegateIfEqual(kUnsignedLessThanOrEqual);
         return VisitWord32Compare(selector, value, cont);
-      case IrOpcode::kWord64Equal: {
-        // Combine with comparisons against 0 by simply inverting the
-        // continuation.
-        Int64BinopMatcher m(value);
-        if (m.right().Is(0)) {
-          user = value;
-          value = m.left().node();
-          cont->Negate();
-          continue;
-        }
+      case IrOpcode::kWord64Equal:
         cont->OverwriteAndNegateIfEqual(kEqual);
         return VisitWord64Compare(selector, value, cont);
-      }
       case IrOpcode::kInt64LessThan:
         cont->OverwriteAndNegateIfEqual(kSignedLessThan);
         return VisitWord64Compare(selector, value, cont);
       case IrOpcode::kInt64LessThanOrEqual:
         cont->OverwriteAndNegateIfEqual(kSignedLessThanOrEqual);
         return VisitWord64Compare(selector, value, cont);
       case IrOpcode::kUint64LessThan:
         cont->OverwriteAndNegateIfEqual(kUnsignedLessThan);
         return VisitWord64Compare(selector, value, cont);
       case IrOpcode::kUint64LessThanOrEqual:
@@ skipping 50 matching lines @@
             }
           }
         }
         break;
       case IrOpcode::kWord32And:
       case IrOpcode::kWord64And:
         return VisitWordCompare(selector, value, kMips64Tst, cont, true);
       default:
         break;
     }
-    break;
   }
 
   // Continuation could not be combined with a compare, emit compare against 0.
   EmitWordCompareZero(selector, value, cont);
 }
 
 }  // namespace
 
 void InstructionSelector::VisitBranch(Node* branch, BasicBlock* tbranch,
                                       BasicBlock* fbranch) {
@@ skipping 331 matching lines @@
   } else {
     DCHECK(kArchVariant == kMips64r2);
     return MachineOperatorBuilder::AlignmentRequirements::
         NoUnalignedAccessSupport();
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8