On Thu, Nov 5, 2015 at 6:08 AM, Alexandre Oliva <aol...@redhat.com> wrote:
> On Sep 23, 2015, Alexandre Oliva <aol...@redhat.com> wrote:
>
>> @@ -2982,38 +2887,39 @@ assign_parm_setup_block (struct assign_parm_data_all
>> *all,
> [snip]
>> + if (GET_CODE (reg) != CONCAT)
>> + stack_parm = reg;
>> + else
>> + /* This will use or allocate a stack slot that we'd rather
>> + avoid. FIXME: Could we avoid it in more cases? */
>> + target_reg = reg;
>
> It turns out that we can, and that helps fixing PR67753. In the end, I
> ended up using the ABI-reserved stack slot if there is one, but just
> allocating an unsplit complex pseudo fixes all remaining cases that used
> to require the allocation of a stack slot. Yay!
>
> As for pr67753 proper, we emitted the store of the PARALLEL entry_parm
> into the stack parm only in the conversion seq, which was ultimately
> emitted after the copy from stack_parm to target_reg that was supposed
> to copy the value originally in entry_parm. So we copied an
> uninitialized stack slot, and the subsequent store in the conversion seq
> was optimized out as dead.
>
> This caused a number of regressions on hppa-linux-gnu. The fix for this
> is to arrange for the copy to target_reg to be emitted in the conversion
> seq if the copy to stack_parm was. I can't determine whether this fix
> all reported regressions, but from visual inspection of the generated
> code I'm pretty sure it fixes at least gcc.c-torture/execute/pr38969.c.
>
>
> When we do NOT have an ABI-reserved stack slot, the store of the
> PARALLEL entry_parm into the intermediate pseudo doesn't need to go in
> the conversion seq (emit_group_store from a PARALLEL to a pseudo only
> uses registers, according to another comment in function.c), so I've
> simplified that case.
>
>
> This was regstrapped on x86_64-linux-gnu, i686-linux-gnu,
> ppc64-linux-gnu, ppc64el-linux-gnu, and cross-build-tested for all
> targets for which I've tested the earlier patches in the patchset.
> Ok to install?
Ok.
Thanks,
Richard.
>
>
> [PR67753] fix copy of PARALLEL entry_parm to CONCAT target_reg
>
> From: Alexandre Oliva <aol...@redhat.com>
>
> In assign_parms_setup_block, the copy of args in PARALLELs from
> entry_parm to stack_parm is deferred to the parm conversion insn seq,
> but the copy from stack_parm to target_reg was inserted in the normal
> copy seq, that is executed before the conversion insn seq. Oops.
>
> We could do away with the need for an actual stack_parm in general,
> which would have avoided the need for emitting the copy to target_reg
> in the conversion seq, but at least on pa, due to the need for stack
> to copy between SI and SF modes, it seems like using the reserved
> stack slot is beneficial, so I put in logic to use a pre-reserved
> stack slot when there is one, and emit the copy to target_reg in the
> conversion seq if stack_parm was set up there.
>
> for gcc/ChangeLog
>
> PR rtl-optimization/67753
> PR rtl-optimization/64164
> * function.c (assign_parm_setup_block): Avoid allocating a
> stack slot if we don't have an ABI-reserved one. Emit the
> copy to target_reg in the conversion seq if the copy from
> entry_parm is in it too. Don't use the conversion seq to copy
> a PARALLEL to a REG or a CONCAT.
> ---
> gcc/function.c | 39 ++++++++++++++++++++++++++++++++++-----
> 1 file changed, 34 insertions(+), 5 deletions(-)
>
> diff --git a/gcc/function.c b/gcc/function.c
> index aaf49a4..156c72b 100644
> --- a/gcc/function.c
> +++ b/gcc/function.c
> @@ -2879,6 +2879,7 @@ assign_parm_setup_block (struct assign_parm_data_all
> *all,
> rtx entry_parm = data->entry_parm;
> rtx stack_parm = data->stack_parm;
> rtx target_reg = NULL_RTX;
> + bool in_conversion_seq = false;
> HOST_WIDE_INT size;
> HOST_WIDE_INT size_stored;
>
> @@ -2895,9 +2896,23 @@ assign_parm_setup_block (struct assign_parm_data_all
> *all,
> if (GET_CODE (reg) != CONCAT)
> stack_parm = reg;
> else
> - /* This will use or allocate a stack slot that we'd rather
> - avoid. FIXME: Could we avoid it in more cases? */
> - target_reg = reg;
> + {
> + target_reg = reg;
> + /* Avoid allocating a stack slot, if there isn't one
> + preallocated by the ABI. It might seem like we should
> + always prefer a pseudo, but converting between
> + floating-point and integer modes goes through the stack
> + on various machines, so it's better to use the reserved
> + stack slot than to risk wasting it and allocating more
> + for the conversion. */
> + if (stack_parm == NULL_RTX)
> + {
> + int save = generating_concat_p;
> + generating_concat_p = 0;
> + stack_parm = gen_reg_rtx (mode);
> + generating_concat_p = save;
> + }
> + }
> data->stack_parm = NULL;
> }
>
> @@ -2938,7 +2953,9 @@ assign_parm_setup_block (struct assign_parm_data_all
> *all,
> mem = validize_mem (copy_rtx (stack_parm));
>
> /* Handle values in multiple non-contiguous locations. */
> - if (GET_CODE (entry_parm) == PARALLEL)
> + if (GET_CODE (entry_parm) == PARALLEL && !MEM_P (mem))
> + emit_group_store (mem, entry_parm, data->passed_type, size);
> + else if (GET_CODE (entry_parm) == PARALLEL)
> {
> push_to_sequence2 (all->first_conversion_insn,
> all->last_conversion_insn);
> @@ -2946,6 +2963,7 @@ assign_parm_setup_block (struct assign_parm_data_all
> *all,
> all->first_conversion_insn = get_insns ();
> all->last_conversion_insn = get_last_insn ();
> end_sequence ();
> + in_conversion_seq = true;
> }
>
> else if (size == 0)
> @@ -3025,11 +3043,22 @@ assign_parm_setup_block (struct assign_parm_data_all
> *all,
> all->first_conversion_insn = get_insns ();
> all->last_conversion_insn = get_last_insn ();
> end_sequence ();
> + in_conversion_seq = true;
> }
>
> if (target_reg)
> {
> - emit_move_insn (target_reg, stack_parm);
> + if (!in_conversion_seq)
> + emit_move_insn (target_reg, stack_parm);
> + else
> + {
> + push_to_sequence2 (all->first_conversion_insn,
> + all->last_conversion_insn);
> + emit_move_insn (target_reg, stack_parm);
> + all->first_conversion_insn = get_insns ();
> + all->last_conversion_insn = get_last_insn ();
> + end_sequence ();
> + }
> stack_parm = target_reg;
> }
>
>
>
> --
> Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
> You must be the change you wish to see in the world. -- Gandhi
> Be Free! -- http://FSFLA.org/ FSF Latin America board member
> Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer
