[turbofan] Changed TruncateFloat64ToInt64 to TryTruncateFloat64ToInt64.

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/frames-arm64.h"
 #include "src/arm64/macro-assembler-arm64.h"
 #include "src/ast/scopes.h"
 #include "src/compiler/code-generator-impl.h"
@@ skipping 15 matching lines @@
       : InstructionOperandConverter(gen, instr) {}
 
   DoubleRegister InputFloat32Register(size_t index) {
     return InputDoubleRegister(index).S();
   }
 
   DoubleRegister InputFloat64Register(size_t index) {
     return InputDoubleRegister(index);
   }
 
+  size_t OutputCount() { return instr_->OutputCount(); }
+
   DoubleRegister OutputFloat32Register() { return OutputDoubleRegister().S(); }
 
   DoubleRegister OutputFloat64Register() { return OutputDoubleRegister(); }
 
   Register InputRegister32(size_t index) {
     return ToRegister(instr_->InputAt(index)).W();
   }
 
   Register InputOrZeroRegister32(size_t index) {
     DCHECK(instr_->InputAt(index)->IsRegister() ||
@@ skipping 984 matching lines @@
     case kArm64Float64ToInt32:
       __ Fcvtzs(i.OutputRegister32(), i.InputDoubleRegister(0));
       break;
     case kArm64Float64ToUint32:
       __ Fcvtzu(i.OutputRegister32(), i.InputDoubleRegister(0));
       break;
     case kArm64Float32ToInt64:
       __ Fcvtzs(i.OutputRegister64(), i.InputFloat32Register(0));
       break;
     case kArm64Float64ToInt64:
-      __ Fcvtzs(i.OutputRegister64(), i.InputDoubleRegister(0));
+      __ Fcvtzs(i.OutputRegister(0), i.InputDoubleRegister(0));
+      if (i.OutputCount() > 1) {
+        UseScratchRegisterScope scope(masm());
+        Label overflow;
+        Label done;
+        __ Fcmp(i.InputDoubleRegister(0), i.InputDoubleRegister(0));
+        __ B(ne, &overflow);
+        __ Cmp(i.OutputRegister(0), i.InputInt64(1));

[Rodolph Perfetta (ARM), 2015/12/04 16:15:45]

Have a look at MacroAssembler::TryConvertDoubleToInt64. It detects overflow and
underflow by comparing to 1 and -1 and checking for overflow. The benefit being
1 and -1 can be encoded in the cmp instructions while INT64_[MIN|MAX] cannot.
the code there also use conditional cmp to avoid some branches. fcmp also has a
coditional variant so all the cmp can be chained without branches.

[ahaas, 2015/12/07 11:00:34]

Done.

+        __ B(eq, &overflow);
+        __ Cmp(i.OutputRegister(0), i.InputInt64(2));
+        __ B(eq, &overflow);
+        __ Mov(i.OutputRegister(1), 1);

[Rodolph Perfetta (ARM), 2015/12/04 16:15:45]

using cset will give you more compact code.

[ahaas, 2015/12/07 11:00:34]

Done.

+        __ B(&done);
+        __ Bind(&overflow);
+        __ Mov(i.OutputRegister(1), 0);
+        __ Bind(&done);
+      }
       break;
     case kArm64Float32ToUint64:
       __ Fcvtzu(i.OutputRegister64(), i.InputFloat32Register(0));
       break;
     case kArm64Float64ToUint64:
       __ Fcvtzu(i.OutputRegister64(), i.InputDoubleRegister(0));
       break;
     case kArm64Int32ToFloat64:
       __ Scvtf(i.OutputDoubleRegister(), i.InputRegister32(0));
       break;
@@ skipping 542 matching lines @@
       padding_size -= kInstructionSize;
     }
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8