[turbofan] Second round of optimisation for unordered comparisons on arm/arm64.

src/compiler/arm64/code-generator-arm64.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/compiler/code-generator.h"
 
 #include "src/arm64/macro-assembler-arm64.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
@@ skipping 763 matching lines @@
         break;
       case kNotEqual:
         __ Tbnz(i.InputRegister64(0), i.InputInt6(1), tlabel);
         break;
       default:
         UNREACHABLE();
     }
   } else {
     switch (condition) {
       case kUnorderedEqual:
-        __ B(vs, flabel);
-      // Fall through.
+        // The "eq" condition will not catch the unordered case.
+        // The jump/fall through to false label will be used if the comparison
+        // was unordered.
       case kEqual:
         __ B(eq, tlabel);
         break;
       case kUnorderedNotEqual:
         // Unordered or not equal can be tested with "ne" condtion.
         // See ARMv8 manual C1.2.3 - Condition Code.
       case kNotEqual:
         __ B(ne, tlabel);
         break;
       case kSignedLessThan:
         __ B(lt, tlabel);
         break;
       case kSignedGreaterThanOrEqual:
         __ B(ge, tlabel);
         break;
       case kSignedLessThanOrEqual:
         __ B(le, tlabel);
         break;
       case kSignedGreaterThan:
         __ B(gt, tlabel);
         break;
       case kUnorderedLessThan:
-        __ B(vs, flabel);
-      // Fall through.
+        // The "lo" condition will not catch the unordered case.
+        // The jump/fall through to false label will be used if the comparison
+        // was unordered.
       case kUnsignedLessThan:
         __ B(lo, tlabel);
         break;
       case kUnorderedGreaterThanOrEqual:
         // Unordered, greater than or equal can be tested with "hs" condtion.
         // See ARMv8 manual C1.2.3 - Condition Code.
       case kUnsignedGreaterThanOrEqual:
         __ B(hs, tlabel);
         break;
       case kUnorderedLessThanOrEqual:
-        __ B(vs, flabel);
-      // Fall through.
+        // The "ls" condition will not catch the unordered case.
+        // The jump/fall through to false label will be used if the comparison
+        // was unordered.
       case kUnsignedLessThanOrEqual:
         __ B(ls, tlabel);
         break;
       case kUnorderedGreaterThan:
         // Unordered or greater than can be tested with "hi" condtion.
         // See ARMv8 manual C1.2.3 - Condition Code.
       case kUnsignedGreaterThan:
         __ B(hi, tlabel);
         break;
       case kOverflow:
@@ skipping 339 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8