[turbofan] Implemented the RoundUint64ToFloat32 TurboFan operator for x64, arm64,

src/ppc/simulator-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 <stdarg.h>
 #include <stdlib.h>
 #include <cmath>
 
 #if V8_TARGET_ARCH_PPC
 
@@ skipping 2690 matching lines @@
     case FCFID: {
       // fcfids
       int frt = instr->RTValue();
       int frb = instr->RBValue();
       double t_val = get_double_from_d_register(frb);
       int64_t* frb_val_p = reinterpret_cast<int64_t*>(&t_val);
       double frt_val = static_cast<float>(*frb_val_p);
       set_d_register_from_double(frt, frt_val);
       return;
     }
+    case FCFIDU: {
+      // fcfidus
+      int frt = instr->RTValue();
+      int frb = instr->RBValue();
+      double t_val = get_double_from_d_register(frb);

[titzer, 2015/11/12 19:06:00]

I'm not entirely certain that get_double_from_d_register doesn't accidentally
alter NaN bits somehow. Maybe we need a get_uint64_from_d_register?

[ahaas, 2015/11/12 20:49:18]

In my understanding the value in this register is the converted uint64_t value,
so this value cannot contain NaN.

[MTBrandyberry, 2015/11/12 23:00:10]

get_d_register, which returns the raw int64 bits, is probably the right answer
here.  I can fix this instance and the others that need it in a follow-on CL.

[MTBrandyberry, 2015/11/13 18:40:38]

See https://codereview.chromium.org/1445603002/ if you want to address this
here.

+      uint64_t* frb_val_p = reinterpret_cast<uint64_t*>(&t_val);
+      double frt_val = static_cast<float>(*frb_val_p);

[ahaas, 2015/11/12 20:49:18]

I think it should be float frt_val, and not double.

[MTBrandyberry, 2015/11/12 23:00:10]

PPC's only floating point register representation is double precision.  Thus the
cast is sufficient to convert to 32-bit float before assigning back to the
register.

+      set_d_register_from_double(frt, frt_val);
+      return;
+    }
   }
   UNIMPLEMENTED();  // Not used by V8.
 }
 
 
 void Simulator::ExecuteExt4(Instruction* instr) {
   switch (instr->Bits(5, 1) << 1) {
     case FDIV: {
       int frt = instr->RTValue();
       int fra = instr->RAValue();
@@ skipping 1233 matching lines @@
   uintptr_t* stack_slot = reinterpret_cast<uintptr_t*>(current_sp);
   uintptr_t address = *stack_slot;
   set_register(sp, current_sp + sizeof(uintptr_t));
   return address;
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // USE_SIMULATOR
 #endif  // V8_TARGET_ARCH_PPC