https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114261
Alexander Monakov <amonakov at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mkuvyrkov at gcc dot gnu.org
--- Comment #5 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
It appears sched-deps is O(N*M) given N reg_pending_barriers and M distinct
pseudos in a region (or even a basic block). For instance, on the following
testcase
#define x10(x) x x x x x x x x x x
#define x100(x) x10(x10(x))
#define x10000(x) x100(x100(x))
void f(int);
void g(int *p)
{
#if 1
x10000(f(*p++);)
#else
x10000(asm("" :: "r"(*p++));)
#endif
}
gcc -O -fschedule-insns invokes add_dependence 20000 times for each asm/call
after the first. There is a loop
for (i = 0; i < (unsigned)deps->max_reg; i++)
{
struct deps_reg *reg_last = &deps->reg_last[i];
reg_last->sets = alloc_INSN_LIST (insn, reg_last->sets);
SET_REGNO_REG_SET (&deps->reg_last_in_use, i);
}
that registers the insn with reg_pending_barrier != 0 in reg_last->sets of each
pseudo, and then all those reg_last->sets will be inspected on the next
reg_pending_barrier insn.
