Implement FixupPrecode for Arm64

[ramarag]

No description provided.

[ramarag]

@kyulee1 how do i debug the issue with the following failure:
http://dotnet-ci.cloudapp.net/job/dotnet_coreclr/job/master/job/arm64_cross_release_windows_nt_pri1r2r_prtest/17/consoleFull#-1176242260420e5adf-a1af-470a-bb97-8255d5af8765

[kyulee1]

Machines are offline and unreachable, which frequently occurred these days.
I took the affected machines out of the pool temporarily.

[ramarag]

@dotnet-bot test Windows_NT arm64 Release pri1r2r

[ramarag]

@dotnet-bot test Windows_NT arm64 Checked

[ramarag]

@dotnet/arm64-contrib @rahku PTAL

[rahku]

in comment forward the call to prestub

[rahku]

In precode.cpp in function Precode::SetTargetInterlocked
following code also applies for arm64. Can you make the change
#if !defined(TARGET_ARM)
if (ret) {
FlushInstructionCache(GetCurrentProcess(),this,SizeOf());
}
#endif

ramrag: done

[rahku]

Is this the disassembly of FixupPrecode::GetMethodDesc()

[ramarag]

NO the assembly for FixupPrecode::GetMethodDesc() generated by C++ compiler is actually

39403c08 ldrb        w8,[x0,#0xF]
d280030a mov         x10,#0x18
11000508 add         w8,w8,#1
93407d09 sxtw        x9,w8
9b0a7d29 mul         x9,x9,x10
f860692a ldr         x10,[x9,x0]
b500006a cbnz        x10,coreclr!FixupPrecode::GetMethodDesc+0x24 (00000001`80145004)
d2800000 mov         x0,#0
14000004 b           coreclr!FixupPrecode::GetMethodDesc+0x30 (00000001`80145010)
39403808 ldrb        w8,[x0,#0xE]
531d7108 lsl         w8,w8,#3
8b28c140 add         x0,x10,w8 sxtw
d65f03c0 ret         lr

I replaced the mul with two add instructions. The assembly code here is similar to what is found in arm

[rahku]

LGTM

[ramarag]

@dotnet-bot test Windows_NT arm64 Release pri1r2r