[Bug target/80782] Configure options to use llvm/clang assembler on Mac
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80782 --- Comment #16 from Iain Sandoe --- (In reply to Eric Gallager from comment #15) > (In reply to Iain Sandoe from comment #12) > > please could you be more specific about exactly what's not working? > > - i.e if you're on an older version of the OS. > > - version of Xcode. > > So I'm assuming that this is the part that this is still in WAITING for? I guess so... cctools 'as' already automatically calls 'clang -cc1as' where the system supports it and GCC's configuration process detects that this is in force (where it matters to assembler options). ... so we are already using this on the platform versions for which Apple defaults to using the LLVM back end (i.e. clang -cc1as) for the assembler. For some versions of Xcode (before this became the default) it would be possible modify the configure to add the '-q' flag to force the use of 'clang -cc1as' instead of the GAS-1.38 based assembler - however, at that point we would clearly be making it possible to generate instructions that the OS toolchain was not expecting, so not sure of how useful it would be. from the original description: > As a result, GCC generates code that fails to assemble when using > optimisation for >any CPU that has support for AVX or newer intrinsics. A > pity and often annoying >because the failure can happen only late during a > build process. We should not be trying to generate such instructions on systems that do not support them - so this implies some different issue is in play.
[Bug target/80782] Configure options to use llvm/clang assembler on Mac
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80782 --- Comment #15 from Eric Gallager --- (In reply to Iain Sandoe from comment #12) > please could you be more specific about exactly what's not working? > - i.e if you're on an older version of the OS. > - version of Xcode. So I'm assuming that this is the part that this is still in WAITING for?
[Bug target/80782] Configure options to use llvm/clang assembler on Mac
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80782 --- Comment #14 from Eric Gallager --- (In reply to Eric Gallager from comment #13) > (In reply to Iain Sandoe from comment #12) > > AFAIK the use of the clang assembler (i.e. calling cctools as which then > > spawns clang -cc1as) is working on all open branches (and on the closed > > 6.5). > > > > please could you be more specific about exactly what's not working? > > - i.e if you're on an older version of the OS. > > - version of Xcode. > > > > Note that the default for which assembler backend is called does depend on > > the Xcode version. > > This is probably material for a separate bug, but the MacPorts package for > GCC 8 uses the clang assembler from the clang-3.4 port on my system, and > apparently all includes flags get passed to it, so it prints out all sorts > of messages like: > > clang: warning: argument unused during compilation: '-I .' > > when compiling with it. The driver specs might need to be hacked to stop > passing '-I' flags to the assembler that it won't use. Currently I'm working > around it by prefixing all '-I' flags with '-Wp,' so that only the > preprocessor sees them, but that doesn't work for other tools (e.g. splint) > that accept '-I' flags but not '-Wp,' flags. It also breaks fortran-style > includes in gfortran since apparently they're different from the kind seen > in the C preprocessor. Note that these excess warnings cause so many testsuite fails that the resulting log becomes too big to mail to the gcc-testresults mailing list. (3.4MB!)
[Bug target/80782] Configure options to use llvm/clang assembler on Mac
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80782 Eric Gallager changed: What|Removed |Added CC||egallager at gcc dot gnu.org --- Comment #13 from Eric Gallager --- (In reply to Iain Sandoe from comment #12) > AFAIK the use of the clang assembler (i.e. calling cctools as which then > spawns clang -cc1as) is working on all open branches (and on the closed 6.5). > > please could you be more specific about exactly what's not working? > - i.e if you're on an older version of the OS. > - version of Xcode. > > Note that the default for which assembler backend is called does depend on > the Xcode version. This is probably material for a separate bug, but the MacPorts package for GCC 8 uses the clang assembler from the clang-3.4 port on my system, and apparently all includes flags get passed to it, so it prints out all sorts of messages like: clang: warning: argument unused during compilation: '-I .' when compiling with it. The driver specs might need to be hacked to stop passing '-I' flags to the assembler that it won't use. Currently I'm working around it by prefixing all '-I' flags with '-Wp,' so that only the preprocessor sees them, but that doesn't work for other tools (e.g. splint) that accept '-I' flags but not '-Wp,' flags. It also breaks fortran-style includes in gfortran since apparently they're different from the kind seen in the C preprocessor.
[Bug target/80782] Configure options to use llvm/clang assembler on Mac
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80782 --- Comment #12 from Iain Sandoe --- AFAIK the use of the clang assembler (i.e. calling cctools as which then spawns clang -cc1as) is working on all open branches (and on the closed 6.5). please could you be more specific about exactly what's not working? - i.e if you're on an older version of the OS. - version of Xcode. Note that the default for which assembler backend is called does depend on the Xcode version.
[Bug target/80782] Configure options to use llvm/clang assembler on Mac
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80782
--- Comment #11 from René J.V. Bertin ---
I'm using 6.3.0 (that was the latest release when I started). It has the same
code in config/darwin.h though:
```
/* When we detect that we're cctools or llvm as, we need to insert the right
additional options. */
#if HAVE_GNU_AS
#define ASM_OPTIONS ""
#else
#define ASM_OPTIONS "%{v} %{w:-W} %{I*}"
#endif
/* Default Darwin ASM_SPEC, very simple. */
#define ASM_SPEC "-arch %(darwin_arch) \
" ASM_OPTIONS " \
%{Zforce_cpusubtype_ALL:-force_cpusubtype_ALL} \
%{static}" ASM_MMACOSX_VERSION_MIN_SPEC
```
I take it that the -q option would be added to the 1st (empty) ASM_OPTIONS
declaration?
On my older 10.9.5 with Xcode 6.x I have
% xcrun -run as -v
Apple Inc version cctools-862, GNU assembler version 1.38
% xcrun -run as -v -q
Apple LLVM version 6.0 (clang-600.0.57) (based on LLVM 3.5svn)
and from MacPorts:
% /opt/local/bin/as -v
Apple Inc version cctools-895, GNU assembler version 1.38
% /opt/local/bin/as -v -q
clang version 4.0.0 (tags/RELEASE_400/final)
I haven't yet figured out why the latter defaults to GNU as despite what its
manpage says, but it seems clear that one cannot take anything for granted as
to -q being the actual default.
In fact, is there code that requires the old GNU as?
[Bug target/80782] Configure options to use llvm/clang assembler on Mac
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80782 Dominique d'Humieres changed: What|Removed |Added Status|UNCONFIRMED |WAITING Last reconfirmed||2017-05-17 Ever confirmed|0 |1 --- Comment #10 from Dominique d'Humieres --- AFAICT clang-as is available with recent Xcode (8, but probably also 7): % as -v Apple LLVM version 8.1.0 (clang-802.0.42) Target: x86_64-apple-darwin16.6.0 The old gnu as can be used with the -Q option % as -Q -v Apple Inc version cctools-898, GNU assembler version 1.38
[Bug target/80782] Configure options to use llvm/clang assembler on Mac
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80782 --- Comment #9 from Andrew Pinski --- (In reply to René J.V. Bertin from comment #7) > (In reply to Jonathan Wakely from comment #6) > > > I assume something like --with-as=llvm-as doesn't work. > > Nope. What GCC version did you try? 6.x or 7.x? There seems to be code to support llvm-as in GCC 7.1.0 as shown in comment #8.
[Bug target/80782] Configure options to use llvm/clang assembler on Mac
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80782
--- Comment #8 from Andrew Pinski ---
This should be easy to do as a target specific specs. There should be already
one which is used for arguments to as.
From config/darwin.h:
410 /* When we detect that we're cctools or llvm as, we need to insert the
right
411additional options. */
412 #if HAVE_GNU_AS
413 #define ASM_OPTIONS ""
414 #else
415 #define ASM_OPTIONS "%{v} %{w:-W} %{I*}"
416 #endif
417
418 /* Default Darwin ASM_SPEC, very simple. */
419 #define ASM_SPEC "-arch %(darwin_arch) \
420 " ASM_OPTIONS " \
421 %{Zforce_cpusubtype_ALL:-force_cpusubtype_ALL} \
422 %{static}" ASM_MMACOSX_VERSION_MIN_SPEC
This was added with:
https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=aaa50706381cfe490cbc7de0f3ec64c76448aaf4
[Bug target/80782] Configure options to use llvm/clang assembler on Mac
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80782 --- Comment #7 from René J.V. Bertin --- (In reply to Jonathan Wakely from comment #6) > I assume something like --with-as=llvm-as doesn't work. Nope. > It would require > configure to know how to detect the llvm assembler and know how to invoke it > correctly. The latter is the bigger problem, and not for configure to solve but for the compiler driver. > If Apple's gas already understands the llvm assembler options then > leveraging that seems sensible. So all that would be needed is a way to > configure GCC to always use -Wa,-q Indeed. As I said in my previous comment: "It would be useful if GCC could be configured to include platform-specific arguments for the default assembler, in this case `-q`." I presume that --with-as="/path/to/as -q" would try to execute an executable called "as -q" but haven't tried.
[Bug target/80782] Configure options to use llvm/clang assembler on Mac
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80782 Jonathan Wakely changed: What|Removed |Added Target||*-*-darwin* Host||*-*-darwin* Summary|Feature request: use the|Configure options to use |llvm/clang assembler on Mac |llvm/clang assembler on Mac Build||*-*-darwin* --- Comment #6 from Jonathan Wakely --- (In reply to René J.V. Bertin from comment #4) > Write a wrapper script that just prepends or appends `-q` to the arguments > and then calls the actual `as` command, and use that wrapper with the > `--with-as` option? Crossing fingers that GCC itself will build... I assume something like --with-as=llvm-as doesn't work. It would require configure to know how to detect the llvm assembler and know how to invoke it correctly. > What I had in mind was calling `clang -cc1as` or even `llvm-as` directly, > with the proper arguments. That ought to give better control over the > generated object code than relying on a 3rd party (Apple) to implement the > GNU -> clang argument translation. If Apple's gas already understands the llvm assembler options then leveraging that seems sensible. So all that would be needed is a way to configure GCC to always use -Wa,-q
