Fixing llvm-shlib to check for the correct host triple on Windows x86

[tannergooding]

Summary

As per https://bugs.llvm.org/show_bug.cgi?id=44127, the CMakeLists.txt for LLVM-C currently checks the wrong host-triple for Windows X86. This results in the official LLVM-C.dll binary being only 9kb in size and containing no exports.

This updates the check to use i686-pc-windows-msvc, which is the default triplet selected by CMake, so that the resulting binaries are as expected.

[whitequark]

I am no longer maintaining the C API.

[Wallbraker]

Thank you for this patch, this looks good to me. But I do not have commit access to can not commit it.

[tstellar]

Why is i686-pc-windows-msvc is correct triple?

[mstorsjo]

In D77945#3423531, @tstellar wrote:

Why is i686-pc-windows-msvc is correct triple?

See D109493 for a more complete explanation of the issue at hand (sorry I wasn't aware of this patch when I made that one). D47381 changed GetHostTriple.cmake so that it by default sets such a triple - previously it was i686-pc-win32 but after that commit, that cmake file sets it to i686-pc-windows-msvc instead - but this file wasn't updated correctly in sync. D109493 which has been committed made the pattern more flexible to accept both forms.

[tstellar]

@mstorsjo Ok, so is this patch no longer needed?

[mstorsjo]

In D77945#3423692, @tstellar wrote:

@mstorsjo Ok, so is this patch no longer needed?

Indeed, this one was superseded by D109493, so this one can be closed.

[tstellar]

In D77945#3424750, @mstorsjo wrote:

In D77945#3423692, @tstellar wrote:

@mstorsjo Ok, so is this patch no longer needed?

Indeed, this one was superseded by D109493, so this one can be closed.

OK, closing.

llvm/tools/llvm-shlib/CMakeLists.txt

if(MSVC)
   set(LLVM_LINK_COMPONENTS
     ${LLVM_DYLIB_COMPONENTS}
     )
 
   llvm_map_components_to_libnames(LIB_NAMES ${LLVM_DYLIB_COMPONENTS})
   list(REMOVE_DUPLICATES LIB_NAMES)
 
   # The python script needs to know whether symbols are prefixed with underscores or not.
-  if(LLVM_HOST_TRIPLE STREQUAL "i686-pc-win32")
+  if(LLVM_HOST_TRIPLE STREQUAL "i686-pc-windows-msvc")
     set(GEN_UNDERSCORE "--underscore")
   else()
     set(GEN_UNDERSCORE "")
   endif()
 
   # Set this name here, not used in multi conf loop,
   # but add script will pick the right one.
   set(LIBSFILE ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/libllvm-c.args)