[clang] [llvm] Add support for Windows hot-patching (PR #138972)

[via llvm-commits]

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+// This verifies that hotpatch function attributes are correctly propagated when compiling directly to OBJ.
+//
+// RUN: %clang_cl -c --target=x86_64-windows-msvc -O2 /Z7 -fms-hotpatch-functions-file=%S/ms-hotpatch-functions.txt /Fo%t.obj %s
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sivadeilra wrote:

We do support hot-patching ARM64 (and ARM64EC / ARM64X), so I don't want to exclude those architectures.

Windows on 32-bit ARM is obsolete and hot-patching was never a target for it.  Even 32-bit x86 is, in theory, hot-patchable, even if the majority of our hot-patches target kernels (and therefore only apply to AMD64 and ARM64).

Is there a reason for checking specific architectures?  This feature is currently only usable by Microsoft engineers, because hot-patches must be signed and this is done only for MS CVE fixes.  There's no danger of enabling these options for other architectures; it won't cause any problems.

https://github.com/llvm/llvm-project/pull/138972