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s390/preempt: disable __preempt_count_add() optimization for PROFILE_ALL_BRANCHES

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gcc 12 does not (always) optimize away code that should only be generated
if parameters are constant and within in a certain range. This depends on
various obscure kernel config options, however in particular
PROFILE_ALL_BRANCHES can trigger this compile error:

In function ‘__atomic_add_const’,
    inlined from ‘__preempt_count_add.part.0’ at ./arch/s390/include/asm/preempt.h:50:3:
./arch/s390/include/asm/atomic_ops.h:80:9: error: impossible constraint in ‘asm’
   80 |         asm volatile(                                                   \
      |         ^~~

Workaround this by simply disabling the optimization for
PROFILE_ALL_BRANCHES, since the kernel will be so slow, that this
optimization won't matter at all.

Reported-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2022-05-06 11:33:19 +02:00
parent 5ace65ebb5
commit 63678eecec
1 changed files with 11 additions and 4 deletions
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15
arch/s390/include/asm/preempt.h
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@ -46,10 +46,17 @@ static inline bool test_preempt_need_resched(void)
static inline void __preempt_count_add(int val)
{
if (__builtin_constant_p(val) && (val >= -128) && (val <= 127))
__atomic_add_const(val, &S390_lowcore.preempt_count);
else
__atomic_add(val, &S390_lowcore.preempt_count);
/*
* With some obscure config options and CONFIG_PROFILE_ALL_BRANCHES
* enabled, gcc 12 fails to handle __builtin_constant_p().
*/
if (!IS_ENABLED(CONFIG_PROFILE_ALL_BRANCHES)) {
if (__builtin_constant_p(val) && (val >= -128) && (val <= 127)) {
__atomic_add_const(val, &S390_lowcore.preempt_count);
return;
}
}
__atomic_add(val, &S390_lowcore.preempt_count);
}
static inline void __preempt_count_sub(int val)