Update cpuinfo.h: add support for Windows ARM64EC

[snnn]

To fix a build error:

src\arm\windows\init-by-logical-sys-info.c(309,17): Error C2065: 'cpuinfo_uarchs': undeclared identifier

In short, Arm64EC is a new application binary interface (ABI) for apps running on Arm devices with an x64 like ABI.

Reference:

1. VC++ predefined-macros
2. ARM64EC overview

[xuhancn]

I checked https://learn.microsoft.com/en-us/cpp/preprocessor/predefined-macros?view=msvc-170
MSVC architecture related defination is complex, suggest to add more comments.

[malfet]

It feels wrong to define CPUINFO_ARCH_X86_64 on ARM platform, please explain why this is necessary for Win ARM64

[malfet]

Defining CPUINFO_ARCH_X86_64 for _M_ARM64EC feels wrong, please explain why this is needed

[snnn]

_M_X64 Defined as the integer literal value 100 for compilations that target x64 processors or ARM64EC. So _M_X64 could be defined when the CPU is actually an ARM CPU.
Here the condition is defined(_M_X64) && !defined(_M_ARM64EC)) . When _M_ARM64EC is 1, the expression is false.

[snnn]

It feels wrong to define CPUINFO_ARCH_X86_64 on ARM platform,

It is the problem I am facing and fixing. _M_X64 is defined when the ABI is ARM64EC. So, without this change, CPUINFO_ARCH_X86_64 is defined when the target ABI is ARM64EC which is target for ARM64 CPUs.

[snnn]

@malfet , would you mind taking another look at this PR? We need this change to make https://github.com/microsoft/onnxruntime work for ARM64EC builds. A lot of Microsoft applications ship with ARM64EC ABI.

[snnn]

Close it since the is no update.