Hi Tomas, Tobias and Tom,
Thanks for asking. Interestingly, I've a patch (attached) from last year that
tackled some of the issues here. The surface problem is that nvptx's march
and misa are related in complicated ways. Specifying an arch defines the
range of valid isa's, and specifying an isa restricts the set of valid arches.
The current approach, which I agree is problematic, is to force these to
be specified (compatibly) on the cc1 command line. Certainly, an error
is better than an abort. My proposed solution was to allow either to
imply a default for the other, and only issue an error if they are explicitly
specified incompatibly.
One reason for supporting this approach was to ultimately support an
-march=native in the driver (calling libcuda.so to determine the hardware
available on the current machine).
The other use case is bumping the "default" nvptx architecture to something
more recent, say sm_53, by providing/honoring a default arch at configure
time.
Alas, it turns out that specifying a recent arch during GCC bootstrap, allows
the build to notice that the backend (now) supports 16-bit floats, which then
prompts libgcc to contain the floathf and fixhf support that would be required.
Then this in turn shows up as a limitation in the middle-end's handling of
libcalls, which I submitted as a patch to back in July 2022:
https://gcc.gnu.org/pipermail/gcc-patches/2022-July/598848.html
That patch hasn't yet been approved, so the whole nvptx -march= patch
series became backlogged/forgotten.
Hopefully, the attached "proof-of-concept" patch looks interesting (food
for thought). If this approach seems reasonable, I'm happy to brush the
dust off, and resubmit it (or a series of pieces) for review.
Best regards,
Roger
--
> -Original Message-
> From: Thomas Schwinge
> Sent: 18 October 2023 11:16
> To: Tobias Burnus
> Cc: gcc-patches@gcc.gnu.org; Tom de Vries ; Roger Sayle
>
> Subject: Re: [Patch] nvptx: Use fatal_error when -march= is missing not an
> assert
> [PR111093]
>
> Hi Tobias!
>
> On 2023-10-16T11:18:45+0200, Tobias Burnus
> wrote:
> > While mkoffload ensures that there is always a -march=, nvptx's
> > cc1 can also be run directly.
> >
> > In my case, I wanted to know which target-specific #define are
> > available; hence, I did run:
> >accel/nvptx-none/cc1 -E -dM < /dev/null which gave an ICE. After
> > some debugging, the reasons was clear (missing -march=) but somehow a
> > (fatal) error would have been nicer than an ICE + debugging.
> >
> > OK for mainline?
>
> Yes, thanks. I think I prefer this over hard-coding some default
> 'ptx_isa_option' --
> but may be convinced otherwise (incremental change), if that's maybe more
> convenient for others? (Roger?)
>
>
> Grüße
> Thomas
>
>
> > nvptx: Use fatal_error when -march= is missing not an assert
> > [PR111093]
> >
> > gcc/ChangeLog:
> >
> > PR target/111093
> > * config/nvptx/nvptx.cc (nvptx_option_override): Issue fatal error
> > instead of an assert ICE when no -march= has been specified.
> >
> > diff --git a/gcc/config/nvptx/nvptx.cc b/gcc/config/nvptx/nvptx.cc
> > index edef39fb5e1..634c31673be 100644
> > --- a/gcc/config/nvptx/nvptx.cc
> > +++ b/gcc/config/nvptx/nvptx.cc
> > @@ -335,8 +335,9 @@ nvptx_option_override (void)
> >init_machine_status = nvptx_init_machine_status;
> >
> >/* Via nvptx 'OPTION_DEFAULT_SPECS', '-misa' always appears on the
> command
> > - line. */
> > - gcc_checking_assert (OPTION_SET_P (ptx_isa_option));
> > + line; but handle the case that the compiler is not run via the
> > + driver. */ if (!OPTION_SET_P (ptx_isa_option))
> > +fatal_error (UNKNOWN_LOCATION, "%<-march=%> must be specified");
> >
> >handle_ptx_version_option ();
> >
> -
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diff --git a/gcc/calls.cc b/gcc/calls.cc
index 6dd6f73..8a18eae 100644
--- a/gcc/calls.cc
+++ b/gcc/calls.cc
@@ -4795,14 +4795,20 @@ emit_library_call_value_1 (int retval, rtx orgfun, rtx
value,
else
{
/* Convert to the proper mode if a promotion has been active. */
- if (GET_MODE (valreg) != outmode)
+ enum machine_mode valmode = GET_MODE (valreg);
+ if (valmode != outmode)
{
int unsignedp = TYPE_UNSIGNED (tfom);
gcc_assert (promote_function_mode (tfom, outmode, ,
