On Tue, Aug 10, 2021 at 10:33 AM Jojo R via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> Some target like RISC-V allow to group vector register as a whole,
> and only operate part of it in fact, but the 'init-regs' pass will add
> initialization
> for uninitialized registers. Add this hook to reject this action for reducing
> instruction.
Are these groups "visible"? That is, are the pseudos multi-reg
pseudos? I wonder
if there's a more generic way to tame down initregs w/o introducing a new target
hook.
Btw, initregs is a red herring - it ideally should go away. See PR61810.
So instead of adding to it can you see whether disabling the pass for RISC-V
works w/o fallout (and add a comment to the PR)? Maybe some more RTL
literate (in particular DF literate) can look at the remaining issue.
Richard, did you
ever have a look into the "issue" that initregs covers up (whatever
that exactly is)?
Thanks,
Richard.
> gcc/
> * init-regs.c (initialize_uninitialized_regs): Call
> register_reject_init_p.
> * target.def (register_reject_init_p): New hook.
> * doc/tm.texi.in: Add TARGET_REGISTER_REJECT_INIT_P.
> * doc/tm.texi: Regenerated.
> ---
> gcc/doc/tm.texi | 6 ++++++
> gcc/doc/tm.texi.in | 2 ++
> gcc/init-regs.c | 5 +++++
> gcc/target.def | 8 ++++++++
> 4 files changed, 21 insertions(+)
>
> diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> index a30fdcbbf3d6..83fd5496ca3f 100644
> --- a/gcc/doc/tm.texi
> +++ b/gcc/doc/tm.texi
> @@ -12588,3 +12588,9 @@ Return an RTX representing @var{tagged_pointer} with
> its tag set to zero.
> Store the result in @var{target} if convenient.
> The default clears the top byte of the original pointer.
> @end deftypefn
> +
> +@deftypefn {Target Hook} bool TARGET_REGISTER_REJECT_INIT_P (rtx @var{reg})
> +This target hook should return @code{true} if reject initialization for a
> uninitialized @var{reg}.
> +
> +The default value of this hook is @code{NULL}.
> +@end deftypefn
> diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
> index 611fc500ac86..13174ce66d59 100644
> --- a/gcc/doc/tm.texi.in
> +++ b/gcc/doc/tm.texi.in
> @@ -8180,3 +8180,5 @@ maintainer is familiar with.
> @hook TARGET_MEMTAG_EXTRACT_TAG
>
> @hook TARGET_MEMTAG_UNTAGGED_POINTER
> +
> +@hook TARGET_REGISTER_REJECT_INIT_P
> diff --git a/gcc/init-regs.c b/gcc/init-regs.c
> index 72e898f3e334..51c0d669d30b 100644
> --- a/gcc/init-regs.c
> +++ b/gcc/init-regs.c
> @@ -21,6 +21,7 @@ along with GCC; see the file COPYING3. If not see
> #include "system.h"
> #include "coretypes.h"
> #include "backend.h"
> +#include "target.h"
> #include "rtl.h"
> #include "tree.h"
> #include "df.h"
> @@ -101,6 +102,10 @@ initialize_uninitialized_regs (void)
> rtx_insn *move_insn;
> rtx reg = DF_REF_REAL_REG (use);
>
> + if (targetm.register_reject_init_p
> + && targetm.register_reject_init_p (reg))
> + continue;
> +
> bitmap_set_bit (already_genned, regno);
>
> start_sequence ();
> diff --git a/gcc/target.def b/gcc/target.def
> index 7676d5e626e3..c2b54421618d 100644
> --- a/gcc/target.def
> +++ b/gcc/target.def
> @@ -4545,6 +4545,14 @@ by a subtarget.",
> unsigned HOST_WIDE_INT, (void),
> NULL)
>
> +/* Return true if reject initialization for a uninitialized register. */
> +DEFHOOK
> +(register_reject_init_p,
> + "This target hook should return @code{true} if reject initialization for a
> uninitialized @var{reg}.\n\
> +\n\
> +The default value of this hook is @code{NULL}.",
> + bool, (rtx reg), NULL)
> +
> /* Functions relating to calls - argument passing, returns, etc. */
> /* Members of struct call have no special macro prefix. */
> HOOK_VECTOR (TARGET_CALLS, calls)
> --
> 2.24.3 (Apple Git-128)
>
