[COFF, ARM64] Declare intrinsics: __nop, _byteswap_[ushort/ulong/uint64]

[mgrang]

Summary

Declare the intrinsics: _byteswap_ushort, _byteswap_long, _byteswap_uint64, __nop

[efriedma]

Have you verified this matches MSVC? (IIRC the only reason we include stdlib.h on x86 is so we can define _mm_malloc.)

[mgrang]

In D56620#1354979, @efriedma wrote:

Have you verified this matches MSVC? (IIRC the only reason we include stdlib.h on x86 is so we can define _mm_malloc.)

I don't see MSVC intrin.h including stdlib.h. So I guess I will just declare the required intrinsics.

[efriedma]

lib/Headers/intrin.h

569

Isn't there already a declaration of __nop in intrin.h? (Line 100.)

[TomTan]

We need full definition for __nop in intrin.h.

lib/Headers/intrin.h

569

For nop, we probably need full definition instead of declaration, just like nop for x86/x64 in this file.

[mgrang]

I have implemented __nop intrinsic in D56671

[mgrang]

_bytswap intrinsics are added in D56685. Abandoning this patch.

lib/Headers/intrin.h

 /*----------------------------------------------------------------------------*\
 |* MS AArch64 specific
 \*----------------------------------------------------------------------------*/
 #if defined(__aarch64__)
 unsigned __int64 __getReg(int);
 long _InterlockedAdd(long volatile *Addend, long Value);
 int _ReadStatusReg(int);
 void _WriteStatusReg(int, int);
+unsigned short _byteswap_ushort (unsigned short val);
+unsigned long _byteswap_ulong (unsigned long val);
+unsigned __int64 _byteswap_uint64 (unsigned __int64 val);
+void __nop();
 #endif
 
 /*----------------------------------------------------------------------------*\
 |* Privileged intrinsics
 \*----------------------------------------------------------------------------*/
 #if defined(__i386__) || defined(__x86_64__)
 static __inline__ unsigned __int64 __DEFAULT_FN_ATTRS
 __readmsr(unsigned long __register) {