https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108653
Bug ID: 108653
Summary: SRA compile-time hog with large copy chain
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: rguenth at gcc dot gnu.org
Target Milestone: ---
PR108500 shows that propagate_all_subaccesses is quadratic in the length of a
copy chain. A simplified testcase looks like the following where adding
'THOUSAND's will increase the number of items worked on in its processing loop
quadratically.
struct s2 {
int id;
char a[20];
};
static inline __attribute__((always_inline)) struct s2
f(struct s2 s)
{
return s;
}
volatile struct s2 x;
int main(void)
{
struct s2 s2 = {0};
#define TEN \
s2 = f(s2); \
s2 = f(s2); \
s2 = f(s2); \
s2 = f(s2); \
s2 = f(s2); \
s2 = f(s2); \
s2 = f(s2); \
s2 = f(s2); \
s2 = f(s2); \
s2 = f(s2);
#define HUNDRED TEN TEN TEN TEN TEN TEN TEN TEN TEN TEN
#define THOUSAND HUNDRED HUNDRED HUNDRED HUNDRED HUNDRED HUNDRED HUNDRED
HUNDRED HUNDRED HUNDRED
THOUSAND THOUSAND
return 0;
}
with a dev build this shows
tree SRA : 0.52 ( 66%) 0.00 ( 0%) 0.53 ( 66%)
0 ( 0%)
