[cfe-dev] Clang on Windows targeting gcc requirements
Edward Diener
eldlistmailingz at tropicsoft.com
Sun Jul 5 07:16:41 PDT 2015
On 7/5/2015 2:29 AM, Yaron Keren wrote:
> clang uses its own *intrin.h files, found in ..\lib\clang\3.7.0\include\
> relative to the bin, which appears before the gcc include directories.
> If you run clang++ -v somefile.cpp you'll see which directory clang
> looks for, it should look something like:
>
> #include <...> search starts here:
> C:\mingw32\i686-w64-mingw32\include\c++
> C:\mingw32\i686-w64-mingw32\include\c++\i686-w64-mingw32
> C:\mingw32\i686-w64-mingw32\include\c++\backward
> * C:\llvm\msvc\RelWithDebInfo\bin\..\lib\clang\3.7.0\include*
> C:\mingw32\lib\gcc\i686-w64-mingw32\4.9.1\include
> C:\mingw32\lib\gcc\i686-w64-mingw32\4.9.1\include-fixed
> C:\mingw32\i686-w64-mingw32\include
> C:\mingw32\include
Look at line 26 of clang's intrin.h. Clang is actually including the
mingw/gcc intrin.h instead of using its own as long as its the gcc
version and not the Windows VC++ version.
>
>
>
> 2015-07-05 8:43 GMT+03:00 Edward Diener
> <eldlistmailingz at tropicsoft.com
> <mailto:eldlistmailingz at tropicsoft.com>>:
>
> On 7/3/2015 10:59 AM, Yaron Keren wrote:
>
> You only need to have the bin directory in your PATH. clang will
> find
> the include and library directory based on the bin directory.
> There are
> no fixed paths, you can put in c:\mingw or wherever.
>
>
> I ran into a problem using mingw-64 and the latest clang. In the
> mingw-64 intrin.h for gcc-4.9 on up it uses the gcc version number
> to decide whether to define the macro __MINGW_FORCE_SYS_INTRINS. If
> this macro is not defined it leads to multiple declarations for
> __m64 and some other CPU feature typdefs. Its gcc implementation
> defines __MINGW_FORCE_SYS_INTRINS for gcc-4.9 on up but clang still
> sets the gcc version number to gcc-4.2.1 so that
> __MINGW_FORCE_SYS_INTRINS is not automatically defined.
>
> My workaround for this was to define __MINGW_FORCE_SYS_INTRINS when
> using clang. This appears to work fine in my tests for clang but
> then I found a link of yours at
> http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20141110/118349.html
> which appears to claim that defining __MINGW_FORCE_SYS_INTRINS
> forces the use of invalid CPU instructions when compiling with clang
> but evidently not when compiling with gcc.
>
> Does merely specifying all the x86-x64 compiler intrinsics, as the
> intrin.h in gcc-4.9 and up does, cause CPU instruction set problems
> when compiling with clang ? If so this means that I cannot use clang
> with gcc-4.9 and up unless I locally change their headers to avoid
> the problem. I have alerted mingw-64 about the general issue.
>
>
>
>
> 2015-07-03 16:13 GMT+03:00 Edward Diener
> <eldlistmailingz at tropicsoft.com
> <mailto:eldlistmailingz at tropicsoft.com>
> <mailto:eldlistmailingz at tropicsoft.com
> <mailto:eldlistmailingz at tropicsoft.com>>>:
>
> On 6/25/2015 2:13 PM, Yaron Keren wrote:
>
> See http://reviews.llvm.org/D5268
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__reviews.llvm.org_D5268&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=CnzuN65ENJ1H9py9XLiRvC_UQz6u3oG6GUNn7_wosSM&m=6v0YYUzHFzH7arlP_9zpzG3JiWS0RZk2iJCNknhFq2w&s=MbW9hMCfmYAvYW_gmgoNZDxw2dkTs9GWeBpSpkJ56Cs&e=>
>
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__reviews.llvm.org_D5268&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=CnzuN65ENJ1H9py9XLiRvC_UQz6u3oG6GUNn7_wosSM&m=ecMMp1TUmHLfiiZ_MlnPwTgmGQGZqkJoByqz4GWmOJ8&s=GyhTLhjqmvS-L0bXc8ytxxjhk6AnpKowj6eW2JYk9i4&e=>
>
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__reviews.llvm.org_D5268&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=CnzuN65ENJ1H9py9XLiRvC_UQz6u3oG6GUNn7_wosSM&m=YgSrUuiAhPt76cF_h_LXb8Mg84W8p9nMvUiL3koHKP4&s=aW_6t6KDGfo5hO6NiTn5Hy9afNhzwfkX-BZHT9PtXmk&e=>
>
>
> I can see that the patch has been applied officially to the
> latest
> clang source. It's in the latest code when I update llvm/clang.
> Thanks very much !
>
> But how do I use it ?
>
> Am I supposed to be able to build clang using a mingw-64
> distro in
> my PATH ?
>
> When I compile with clang how do I tell it to use the mingw-64
> headers and RTL ? Does it matter whether the mingw-64
> distro is 32
> bit or 64 bit ?
>
> Do I need to have the mingw-64 distro at c:\mingw ?
>
> I am willing to test this for clang and report back results
> here,
> since I can easily switch between mingw-64 distros ( 4.8.4,
> 4.9.2,
> 5.1 ) and I test a number of Boost libraries including my
> own with
> clang, but I need a little information on how to do it.
>
>
>
>
> 2015-06-25 10:46 GMT+03:00 Edward Diener
>
> <eldlistmailingz at tropicsoft.com
> <mailto:eldlistmailingz at tropicsoft.com>
>
> <mailto:eldlistmailingz at tropicsoft.com
> <mailto:eldlistmailingz at tropicsoft.com>>
>
> <mailto:eldlistmailingz at tropicsoft.com
> <mailto:eldlistmailingz at tropicsoft.com>
>
>
> <mailto:eldlistmailingz at tropicsoft.com
> <mailto:eldlistmailingz at tropicsoft.com>>>>:
>
>
> For either the latest clang built from souce on
> Windows or
> a binary
> distribution of clang on Windows it appears that clang
> expects the
> supporting gcc include files and lib files to be
> in the
> hardcoded
> directory:
>
> c:\mingw
>
> and follow the mingw directory structure.
>
> 1) Can this please be changed in the future so
> that some
> environment
> variable ( maybe CLANG_GCC ) can be set to the gcc
> installation
> rather than use a hardcoded path ?
>
> 2) Can clang be updated to support the mingw-64
> directory
> structure
> and not just the mingw directory structure ? The
> mingw-64
> distros
> seem now to be the preferred gcc distributions on
> Windows and
> support the latest versions of gcc.
>
> Do I need to make these suggestions on the clang bug
> tracker for the
> suggestions to be seriously considered ?
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