PPC/s390: [turbofan] Refactor the compare-zero folding in instruction selector.

src/compiler/ppc/instruction-selector-ppc.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/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 #include "src/ppc/frames-ppc.h"
 
@@ skipping 1584 matching lines @@
   Node* right = node->InputAt(1);
   VisitCompare(selector, kPPC_CmpDouble, g.UseRegister(left),
                g.UseRegister(right), cont);
 }
 
 
 // Shared routine for word comparisons against zero.
 void VisitWordCompareZero(InstructionSelector* selector, Node* user,
                           Node* value, InstructionCode opcode,
                           FlagsContinuation* cont) {
-  while (selector->CanCover(user, value)) {
+  // Try to combine with comparisons against 0 by simply inverting the branch.
+  while (value->opcode() == IrOpcode::kWord32Equal &&
+         selector->CanCover(user, value)) {
+    Int32BinopMatcher m(value);
+    if (!m.right().Is(0)) break;
+
+    user = value;
+    value = m.left().node();
+    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:
@@ skipping 101 matching lines @@
 // case IrOpcode::kWord64Or:
 // case IrOpcode::kWord64Xor:
 // case IrOpcode::kWord64Sar:
 // case IrOpcode::kWord64Shl:
 // case IrOpcode::kWord64Shr:
 // case IrOpcode::kWord64Ror:
 #endif
       default:
         break;
     }
-    break;
   }
 
   // Branch could not be combined with a compare, emit compare against 0.
   PPCOperandGenerator g(selector);
   VisitCompare(selector, opcode, g.UseRegister(value), g.TempImmediate(0),
                cont);
 }
 
 
 void VisitWord32CompareZero(InstructionSelector* selector, Node* user,
@@ skipping 341 matching lines @@
 // static
 MachineOperatorBuilder::AlignmentRequirements
 InstructionSelector::AlignmentRequirements() {
   return MachineOperatorBuilder::AlignmentRequirements::
       FullUnalignedAccessSupport();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8