r280133. Original commit message:
C++ Modules TS: driver support for building modules.
This works as follows: we add --precompile to the existing gamut of options for
specifying how far to go when compiling an input (-E, -c, -S, etc.). This flag
specifies that an input is taken to the precompilation step and no further, and
this can be specified when building a .pcm from a module interface or when
building a .pch from a header file.
The .cppm extension (and some related extensions) are implicitly recognized as
C++ module interface files. If --precompile is /not/ specified, the file is
compiled (via a .pcm) to a .o file containing the code for the module (and then
potentially also assembled and linked, if -S, -c, etc. are not specified). We
do not yet suppress the emission of object code for other users of the module
interface, so for now this will only work if everything in the .cppm file has
vague linkage.
As with the existing support for module-map modules, prebuilt modules can be
provided as compiler inputs either via the -fmodule-file= command-line argument
or via files named ModuleName.pcm in one of the directories specified via
-fprebuilt-module-path=.
This also exposes the -fmodules-ts cc1 flag in the driver. This is still
experimental, and in particular, the concrete syntax is subject to change as
the Modules TS evolves in the C++ committee. Unlike -fmodules, this flag does
not enable support for implicitly loading module maps nor building modules via
the module cache, but those features can be turned on separately and used in
conjunction with the Modules TS support.
llvm-svn: 280134
This works as follows: we add --precompile to the existing gamut of options for
specifying how far to go when compiling an input (-E, -c, -S, etc.). This flag
specifies that an input is taken to the precompilation step and no further, and
this can be specified when building a .pcm from a module interface or when
building a .pch from a header file.
The .cppm extension (and some related extensions) are implicitly recognized as
C++ module interface files. If --precompile is /not/ specified, the file is
compiled (via a .pcm) to a .o file containing the code for the module (and then
potentially also assembled and linked, if -S, -c, etc. are not specified). We
do not yet suppress the emission of object code for other users of the module
interface, so for now this will only work if everything in the .cppm file has
vague linkage.
As with the existing support for module-map modules, prebuilt modules can be
provided as compiler inputs either via the -fmodule-file= command-line argument
or via files named ModuleName.pcm in one of the directories specified via
-fprebuilt-module-path=.
This also exposes the -fmodules-ts cc1 flag in the driver. This is still
experimental, and in particular, the concrete syntax is subject to change as
the Modules TS evolves in the C++ committee. Unlike -fmodules, this flag does
not enable support for implicitly loading module maps nor building modules via
the module cache, but those features can be turned on separately and used in
conjunction with the Modules TS support.
llvm-svn: 280035
Now that pragma comment and pragma detect_mismatch are implemented, this might
just work.
Some pragmas aren't serialized yet (from the top of my head: code_seg, bss_seg,
data_seg, const_seg, init_seg, section, vtordisp), but these are as far as I
know usually pushed and popped within the header and usually don't leak out.
If it turns out the current PCH support isn't good enough yet, we can turn it
off again.
llvm-svn: 262749
In the gcc precompiled header model, one explicitly runs clang with `-x
c++-header` on a .h file to produce a gch file, and then includes the header
with `-include foo.h` and if a .gch file exists for that header it gets used.
This is documented at
http://clang.llvm.org/docs/UsersManual.html#precompiled-headers
cl.exe's model is fairly different, and controlled by the two flags /Yc and
/Yu. A pch file is generated as a side effect of a regular compilation when
/Ycheader.h is passed. While the compilation is running, the compiler keeps
track of #include lines in the main translation unit and writes everything up
to an `#include "header.h"` line into a pch file. Conversely, /Yuheader.h tells
the compiler to skip all code in the main TU up to and including `#include
"header.h"` and instead load header.pch. (It's also possible to use /Yc and /Yu
without an argument, in that case a `#pragma hrdstop` takes the role of
controlling the point where pch ends and real code begins.)
This patch implements limited support for this in that it requires the pch
header to be passed as a /FI force include flag – with this restriction,
it can be implemented almost completely in the driver with fairly small amounts
of code. For /Yu, this is trivial, and for /Yc a separate pch action is added
that runs before the actual compilation. After r261774, the first failing
command makes a compilation stop – this means if the pch fails to build the
main compilation won't run, which is what we want. However, in /fallback builds
we need to run the main compilation even if the pch build fails so that the
main compilation's fallback can run. To achieve this, add a ForceSuccessCommand
that pretends that the pch build always succeeded in /fallback builds (the main
compilation will then fail to open the pch and run the fallback cl.exe
invocation).
If /Yc /Yu are used in a setup that clang-cl doesn't implement yet, clang-cl
will now emit a "not implemented yet; flag ignored" warning that can be
disabled using -Wno-clang-cl-pch.
Since clang-cl doesn't yet serialize some important things (most notably
`pragma comment(lib, ...)`, this feature is disabled by default and only
enabled by an internal driver flag. Once it's more stable, this internal flag
will disappear.
(The default stdafx.h setup passes stdafx.h as explicit argument to /Yc but not
as /FI – instead every single TU has to `#include <stdafx.h>` as first thing it
does. Implementing support for this should be possible with the approach in
this patch with minimal frontend changes by passing a --stop-at / --start-at
flag from the driver to the frontend. This is left for a follow-up. I don't
think we ever want to support `#pragma hdrstop`, and supporting it with this
approach isn't easy: This approach relies on the driver knowing the pch
filename in advance, and `#pragma hdrstop(out.pch)` can set the output
filename, so the driver can't know about it in advance.)
clang-cl now also honors /Fp and puts pch files in the same spot that cl.exe
would put them, but the pch file format is of course incompatible. This has
ramifications on /fallback, so /Yc /Yu aren't passed through to cl.exe in
/fallback builds.
http://reviews.llvm.org/D17695
llvm-svn: 262420
Richard Smith