Hi!
On 2024-06-25T10:07:47+0100, Richard Sandiford <richard.sandif...@arm.com>
wrote:
> Thomas Schwinge <tschwi...@baylibre.com> writes:
>> On 2024-06-20T14:34:18+0100, Richard Sandiford <richard.sandif...@arm.com>
>> wrote:
>>> This patch adds a combine pass that runs late in the pipeline.
>>> [...]
>>
>> Nice!
>>
>>> The patch [...] disables the pass by default on i386, rs6000
>>> and xtensa.
>>
>> Like here:
>>
>>> --- a/gcc/config/i386/i386-options.cc
>>> +++ b/gcc/config/i386/i386-options.cc
>>> @@ -1942,6 +1942,10 @@ ix86_override_options_after_change (void)
>>> flag_cunroll_grow_size = flag_peel_loops || optimize >= 3;
>>> }
>>>
>>> + /* Late combine tends to undo some of the effects of STV and RPAD,
>>> + by combining instructions back to their original form. */
>>> + if (!OPTION_SET_P (flag_late_combine_instructions))
>>> + flag_late_combine_instructions = 0;
>>> }
>>
>> ..., I think also here:
>>
>>> --- a/gcc/config/rs6000/rs6000.cc
>>> +++ b/gcc/config/rs6000/rs6000.cc
>>> @@ -4768,6 +4768,14 @@ rs6000_option_override_internal (bool global_init_p)
>>> targetm.expand_builtin_va_start = NULL;
>>> }
>>>
>>> + /* One of the late-combine passes runs after register allocation
>>> + and can match define_insn_and_splits that were previously used
>>> + only before register allocation. Some of those define_insn_and_splits
>>> + use gen_reg_rtx unconditionally. Disable late-combine by default
>>> + until the define_insn_and_splits are fixed. */
>>> + if (!OPTION_SET_P (flag_late_combine_instructions))
>>> + flag_late_combine_instructions = 0;
>>> +
>>> rs6000_override_options_after_change ();
>>
>> ..., this needs to be done in 'rs6000_override_options_after_change'
>> instead of 'rs6000_option_override_internal', to address the PRs under
>> discussion. I'm testing such a patch.
>
> Oops! Sorry about that, and thanks for tracking it down.
No worries. ;-) OK to push the attached
"rs6000: Properly default-disable late-combine passes [PR106594, PR115622,
PR115633]"?
Grüße
Thomas
>From ccd12107fb06017f878384d2186ed5f01a1dab79 Mon Sep 17 00:00:00 2001
From: Thomas Schwinge <tschwi...@baylibre.com>
Date: Tue, 25 Jun 2024 10:55:41 +0200
Subject: [PATCH] rs6000: Properly default-disable late-combine passes
[PR106594, PR115622, PR115633]
..., so that it also works for '__attribute__ ((optimize("[...]")))' etc.
PR target/106594
PR target/115622
PR target/115633
gcc/
* config/rs6000/rs6000.cc (rs6000_option_override_internal): Move
default-disable of late-combine passes from here...
(rs6000_override_options_after_change): ... to here.
---
gcc/config/rs6000/rs6000.cc | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index f39b8909925..713fac75f26 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -3431,6 +3431,14 @@ rs6000_override_options_after_change (void)
/* If we are inserting ROP-protect instructions, disable shrink wrap. */
if (rs6000_rop_protect)
flag_shrink_wrap = 0;
+
+ /* One of the late-combine passes runs after register allocation
+ and can match define_insn_and_splits that were previously used
+ only before register allocation. Some of those define_insn_and_splits
+ use gen_reg_rtx unconditionally. Disable late-combine by default
+ until the define_insn_and_splits are fixed. */
+ if (!OPTION_SET_P (flag_late_combine_instructions))
+ flag_late_combine_instructions = 0;
}
#ifdef TARGET_USES_LINUX64_OPT
@@ -4768,14 +4776,6 @@ rs6000_option_override_internal (bool global_init_p)
targetm.expand_builtin_va_start = NULL;
}
- /* One of the late-combine passes runs after register allocation
- and can match define_insn_and_splits that were previously used
- only before register allocation. Some of those define_insn_and_splits
- use gen_reg_rtx unconditionally. Disable late-combine by default
- until the define_insn_and_splits are fixed. */
- if (!OPTION_SET_P (flag_late_combine_instructions))
- flag_late_combine_instructions = 0;
-
rs6000_override_options_after_change ();
/* If not explicitly specified via option, decide whether to generate indexed
--
2.34.1
