ARM64: Prevent compilers to optimize away NaN negation in tests.

src/arm64/simulator-arm64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2812 matching lines @@
 
 
 void Simulator::VisitFPDataProcessing3Source(Instruction* instr) {
   AssertSupportedFPCR();
 
   unsigned fd = instr->Rd();
   unsigned fn = instr->Rn();
   unsigned fm = instr->Rm();
   unsigned fa = instr->Ra();
 
-  // The C99 (and C++11) fma function performs a fused multiply-accumulate.
   switch (instr->Mask(FPDataProcessing3SourceMask)) {
     // fd = fa +/- (fn * fm)
     case FMADD_s: set_sreg(fd, FPMulAdd(sreg(fa), sreg(fn), sreg(fm))); break;
     case FMSUB_s: set_sreg(fd, FPMulAdd(sreg(fa), -sreg(fn), sreg(fm))); break;
     case FMADD_d: set_dreg(fd, FPMulAdd(dreg(fa), dreg(fn), dreg(fm))); break;
     case FMSUB_d: set_dreg(fd, FPMulAdd(dreg(fa), -dreg(fn), dreg(fm))); break;
     // Negated variants of the above.
     case FNMADD_s:
       set_sreg(fd, FPMulAdd(-sreg(fa), -sreg(fn), sreg(fm)));
       break;
@@ skipping 793 matching lines @@
     default:
       UNIMPLEMENTED();
   }
 }
 
 #endif  // USE_SIMULATOR
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM64