[turbofan] Add CalleeSavedFPRegisters to CallDescriptor.

src/compiler/arm64/linkage-arm64.cc

Index: src/compiler/arm64/linkage-arm64.cc
diff --git a/src/compiler/arm64/linkage-arm64.cc b/src/compiler/arm64/linkage-arm64.cc
index 745eb5cde694cc676552b9f32cb42cd84e33ea87..ac0dd0459ad02c80e1dd90c6e5fb4b9732f3d202 100644
--- a/src/compiler/arm64/linkage-arm64.cc
+++ b/src/compiler/arm64/linkage-arm64.cc
@@ -23,6 +23,10 @@ struct Arm64LinkageHelperTraits {
     // TODO(dcarney): correct callee saved registers.
     return 0;
   }
+  static RegList CCalleeSaveFPURegisters() {
+    // TODO(palfia): finish.
+    return 0;

[paul.l..., 2015/06/15 23:05:17]

arm64 has CPURegList::GetCallerSaved() & CPURegList::GetCallerSavedFP, and they
also have MacroAssembler::PushCPURegList(). You'll want to be careful that
whatever methods you use for save/restore are no slower than the stp/ldp
(register pair) operations that they use in the existing TF code.

[akos.palfi.imgtec, 2015/06/22 17:33:20]

OK, I'm generating the same stp/ldp code.

+  }
   static Register CRegisterParameter(int i) {
     static Register register_parameters[] = {x0, x1, x2, x3, x4, x5, x6, x7};
     return register_parameters[i];