From: Georg-Johann Lay <avr@gjlay.de>
To: Richard Biener <richard.guenther@gmail.com>
Cc: gcc-patches@gcc.gnu.org
Subject: [avr,committed]: Implement PR104327 for avr
Date: Thu, 25 May 2023 19:55:15 +0200 [thread overview]
Message-ID: <313b5291-80f1-01db-f74c-da7176853eb0@gjlay.de> (raw)
In-Reply-To: <86AC10B7-7919-4FC7-B36E-7CC2DABE444E@gmail.com>
Am 25.05.23 um 17:07 schrieb Richard Biener:
>
>
>> Am 25.05.2023 um 16:22 schrieb Georg-Johann Lay <avr@gjlay.de>:
>>
>>
>>
>>> Am 25.05.23 um 08:35 schrieb Richard Biener:
>>>> On Wed, May 24, 2023 at 5:44 PM Georg-Johann Lay <avr@gjlay.de> wrote:
>>>> Am 24.05.23 um 11:38 schrieb Richard Biener:
>>>>> On Tue, May 23, 2023 at 2:56 PM Georg-Johann Lay <avr@gjlay.de> wrote:
>>>>>>
>>>>>> PR target/104327 not only affects s390 but also avr:
>>>>>> The avr backend pre-sets some options depending on optimization level.
>>>>>> The inliner then thinks that always_inline functions are not eligible
>>>>>> for inlining and terminates with an error.
>>>>>>
>>>>>> Proposing the following patch that implements TARGET_CAN_INLINE_P.
>>>>>>
>>>>>> Ok to apply?
>>>>>>
>>>>>> Johann
>>>>>>
>>>>>> target/104327: Allow more inlining between different optimization levels.
>>>>>>
>>>>>> avr-common.cc introduces the following options that are set depending
>>>>>> on optimization level: -mgas-isr-prologues, -mmain-is-OS-task and
>>>>>> -fsplit-wide-types-early. The inliner thinks that different options
>>>>>> disallow cross-optimization inlining, so provide can_inline_p.
>>>>>>
>>>>>> gcc/
>>>>>> PR target/104327
>>>>>> * config/avr/avr.cc (avr_can_inline_p): New static function.
>>>>>> (TARGET_CAN_INLINE_P): Define to that function.
>>>>>> diff --git a/gcc/config/avr/avr.cc b/gcc/config/avr/avr.cc
>>>>>> index 9fa50ca230d..55b48f63865 100644
>>>>>> --- a/gcc/config/avr/avr.cc
>>>>>> +++ b/gcc/config/avr/avr.cc
>>>>>> @@ -1018,6 +1018,22 @@ avr_no_gccisr_function_p (tree func)
>>>>>> return avr_lookup_function_attribute1 (func, "no_gccisr");
>>>>>> }
>>>>>>
>>>>>> +
>>>>>> +/* Implement `TARGET_CAN_INLINE_P'. */
>>>>>> +/* Some options like -mgas_isr_prologues depend on optimization level,
>>>>>> + and the inliner might think that due to different options, inlining
>>>>>> + is not permitted; see PR104327. */
>>>>>> +
>>>>>> +static bool
>>>>>> +avr_can_inline_p (tree /* caller */, tree callee)
>>>>>> +{
>>>>>> + // For now, dont't allow to inline ISRs. If the user actually wants
>>>>>> + // to inline ISR code, they have to turn the body of the ISR into an
>>>>>> + // ordinary function.
>>>>>> +
>>>>>> + return ! avr_interrupt_function_p (callee);
>>>>>
>>>>> I'm not sure if AVR has ISA extensions but the above will likely break
>>>>> things like
>>>>>
>>>>> void __attribute__((target("-mX"))) foo () { asm ("isa X opcode");
>>>>> stmt-that-generates-X-ISA; }
>>>>
>>>> This yields
>>>>
>>>> warning: target attribute is not supported on this machine [-Wattributes]
>>> Ah, that's an interesting fact. So that indeed leaves
>>> __attribute__((optimize(...)))
>>> influencing the set of active target attributes via the generic option target
>>> hooks like in your case the different defaults.
>>>> avr has -mmcu=<arch> target options, but switching them in mid-air
>>>> won't work because the file prologue might already be different
>>>> and incompatible across different architectures. And I never
>>>> saw any user requesting such a thing, and I can't imagine
>>>> any reasonable use case... If the warning is not strong enough,
>>>> may be it can be turned into an error, but -Wattributes is not
>>>> specific enough for that.
>>> Note the target attribute is then simply ignored.
>>>>> void bar ()
>>>>> {
>>>>> if (cpu-has-X)
>>>>> foo ();
>>>>> }
>>>>>
>>>>> if always-inlines are the concern you can use
>>>>>
>>>>> bool always_inline
>>>>> = (DECL_DISREGARD_INLINE_LIMITS (callee)
>>>>> && lookup_attribute ("always_inline",
>>>>> DECL_ATTRIBUTES (callee)));
>>>>> /* Do what the user says. */
>>>>> if (always_inline)
>>>>> return true;
>>>>>
>>>>> return default_target_can_inline_p (caller, callee);
>>>>
>>>> The default implementation of can_inline_p worked fine for avr.
>>>> As far as I understand, the new behavior is due to clean-up
>>>> of global states for options?
>>> I think the last change was r8-2658-g9b25e12d2d940a which
>>> for targets without target attribute support made it more likely
>>> to run into the default hook actually comparing the options.
>>> Previously the "default" was oddly special-cased but you
>>> could have still run into compares with two different set of
>>> defaults when there's another "default" default. Say, compile
>>> with -O2 and have one optimize(0) and one optimize(Os)
>>> function it would compare the optimize(0) and optimize(Os)
>>> set if they were distinct from the -O2 set. That probably never
>>> happened for AVR.
>>>> So I need to take into account inlining costs and decide on that
>>>> whether it's preferred to inline a function or not?
>>> No, the hook isn't about cost, it's about full incompatibility. So
>>> if the different -m options that could be in effect for AVR in
>>> a single TU for different functions never should prevent inlining
>>> then simply make the hook return true. If there's a specific
>>> option (that can differ from what specified on the compiler
>>> command line!) that should, then you should compare the
>>> setting of that option from the DECL_FUNCTION_SPECIFIC_TARGET
>>> of the caller and the callee.
>>> But as far as I can see simply returning true should be correct
>>> for AVR, or like your patch handle interrupts differently (though
>>> the -Winline diagnostic will tell the user there's a mismatch in
>>> target options which might be confusing).
>>
>> Ok, simply "true" sounds reasonable. Is that change ok then?
>
> Yes.
>
> Richard
Committed as https://gcc.gnu.org/r14-1245
Johann
--- a/gcc/config/avr/avr.cc
+++ b/gcc/config/avr/avr.cc
@@ -1018,6 +1018,19 @@ avr_no_gccisr_function_p (tree func)
return avr_lookup_function_attribute1 (func, "no_gccisr");
}
+
+/* Implement `TARGET_CAN_INLINE_P'. */
+/* Some options like -mgas_isr_prologues depend on optimization level,
+ and the inliner might think that due to different options, inlining
+ is not permitted; see PR104327. */
+
+static bool
+avr_can_inline_p (tree /* caller */, tree /* callee */)
+{
+ // No restrictions whatsoever.
+ return true;
+}
+
/* Implement `TARGET_SET_CURRENT_FUNCTION'. */
/* Sanity cheching for above function attributes. */
@@ -14770,6 +14783,9 @@ avr_float_lib_compare_returns_bool (machine_mode
mode, enum rtx_code)
#undef TARGET_MD_ASM_ADJUST
#define TARGET_MD_ASM_ADJUST avr_md_asm_adjust
+#undef TARGET_CAN_INLINE_P
+#define TARGET_CAN_INLINE_P avr_can_inline_p
+
struct gcc_target targetm = TARGET_INITIALIZER;
\f
prev parent reply other threads:[~2023-05-25 17:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <7a3552f0-ac4d-754f-a7ba-cba3ff9a4a41@gjlay.de>
2023-05-23 12:55 ` [patch]: " Georg-Johann Lay
2023-05-24 9:38 ` Richard Biener
2023-05-24 15:44 ` Georg-Johann Lay
2023-05-25 6:35 ` Richard Biener
2023-05-25 14:22 ` Georg-Johann Lay
2023-05-25 15:07 ` Richard Biener
2023-05-25 17:55 ` Georg-Johann Lay [this message]
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