[reactos] 04/10: [CMAKE] Explicitly target Pentium for clang. CORE-17202

[Thomas Faber]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=a81788e5bfb95e2db22812...

commit a81788e5bfb95e2db22812c268f35a6de59b793f
Author:     Thomas Faber [e-mail]
AuthorDate: Sat Aug 15 21:41:32 2020 +0200
Commit:     Thomas Faber [e-mail]
CommitDate: Sun Aug 23 12:07:37 2020 +0200

[CMAKE] Explicitly target Pentium for clang. CORE-17202

The MSVC-compatible /arch:IA32 option switches to i386 mode, which
    makes clang avoid 486/Pentium-specific instructions, e.g. cmpxchg8b.
---
 sdk/cmake/msvc.cmake | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/sdk/cmake/msvc.cmake b/sdk/cmake/msvc.cmake
index 0039d71e9de..94847a84167 100644
--- a/sdk/cmake/msvc.cmake
+++ b/sdk/cmake/msvc.cmake
@@ -51,7 +51,12 @@ endif()
 # HACK: for VS 11+ we need to explicitly disable SSE, which is off by
 # default for older compilers. See CORE-6507
 if(ARCH STREQUAL "i386")
-    add_compile_flags("/arch:IA32")
+    # Clang's IA32 means i386, which doesn't have cmpxchg8b
+    if(USE_CLANG_CL)
+        add_compile_flags("-march=${OARCH}")
+    else()
+        add_compile_flags("/arch:IA32")
+    endif()
 endif()

# VS 12+ requires /FS when used in parallel compilations