[Bug target/65181] Support for alloca in nvptx

[Bug target/65181] Support for alloca in nvptx

[tschwinge at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65181

--- Comment #1 from Thomas Schwinge <tschwinge at gcc dot gnu.org> ---
Author: tschwinge
Date: Mon Feb 23 17:51:41 2015
New Revision: 220915

URL: https://gcc.gnu.org/viewcvs?rev=220915&root=gcc&view=rev
Log:
[PR target/65181] nvptx libgcc: Prevent building "advanced" stuff (for example,
gcov support)

When building GCC against a proper newlib sysroot, the libgcc build will
include more than what's built in the -Dinhibit_libc configuration used when
building newlib as part of the GCC build process.  See the inhibit_libc logic
in gcc/configure.ac.

To avoid...

    ptxas _gcov_indirect_call_topn_profiler.o, line 101; error   : Type or
alignment of argument does not match formal parameter 'ptr'
    ptxas _gcov_indirect_call_topn_profiler.o, line 101; error   : Call has
wrong number of parameters
    ptxas _gcov_indirect_call_topn_profiler.o, line 101; error   : Type or
alignment of argument does not match formal parameter 'size'
    ptxas fatal   : Ptx assembly aborted due to errors
    nvptx-as: ptxas returned 255 exit status
    make[2]: *** [_gcov_indirect_call_topn_profiler.o] Error 1

..., "dumb down" the libgcc build:

    libgcc/
    PR target/65181
    * config/nvptx/t-nvptx (INHIBIT_LIBC_CFLAGS): Define to
    -Dinhibit_libc.

Modified:
    trunk/libgcc/ChangeLog
    trunk/libgcc/config/nvptx/t-nvptx

[Bug target/65181] Support for alloca in nvptx

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65181

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |openacc
                 CC|                            |burnus at gcc dot gnu.org

--- Comment #4 from Tobias Burnus <burnus at gcc dot gnu.org> ---
Slightly stupid example which currently fails with:
  sorry, unimplemented: target cannot support alloca.
  x86_64-none-linux-gnu-accel-nvptx-none-gcc returned 1 exit status

call foo(10)
contains
subroutine foo(nn)
  !$acc parallel
  block
    real :: array(nn), array2(10)
    array = [(3*i,i=1,nn)]
    !print *, array
    !$acc loop gang private(array)
    do i = 1, 10
      array(i) = i
      array2(i) = array(i)
    end do
    !print *, array
    !print *, array2
  end block
  !$acc end parallel
end
end

[Bug target/65181] Support for alloca in nvptx

[tschwinge at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65181

--- Comment #5 from Thomas Schwinge <tschwinge at gcc dot gnu.org> ---
While reviewing other things, I found that "'alloca' is a preview feature in
PTX ISA version 7.3", and "requires 'sm_52' or higher".  That got published
2021-05, so it'll be a while until we can reliably use it, but we're getting
there...  ;-)