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

src/compiler/arm/code-generator-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/compiler/code-generator.h"
 
 #include "src/arm/macro-assembler-arm.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
@@ skipping 669 matching lines @@
 }
 
 
 // Assembles branches after an instruction.
 void CodeGenerator::AssembleArchBranch(Instruction* instr, BranchInfo* branch) {
   ArmOperandConverter i(this, instr);
   Label* tlabel = branch->true_label;
   Label* flabel = branch->false_label;
   switch (branch->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 ARMv7 manual A8.3 - Conditional execution.
     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 ARMv7 manual A8.3 - Conditional execution.
     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 ARMv7 manual A8.3 - Conditional execution.
     case kUnsignedGreaterThan:
       __ b(hi, tlabel);
       break;
     case kOverflow:
@@ skipping 364 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8