https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100220
Jan Hubicka <hubicka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Depends on| |100314
--- Comment #3 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
Here the stack frame size of i is stimated to 244 bytes
void i ()
{
int p[8];
int n[27];
int k[24];
int l;
int j;
int _1;
int _2;
int _3;
int c.2_4;
int _5;
<bb 2> [local count: 236223200]:
l = 0;
k = {};
h = &n;
_1 = n[0];
_2 = _1 & 1;
if (_2 != 0)
goto <bb 8>; [50.00%]
else
goto <bb 5>; [50.00%]
<bb 8> [local count: 118111600]:
goto <bb 4>; [100.00%]
<bb 3> [local count: 955630225]:
_3 = c.2_4 + -1;
c = _3;
<bb 4> [local count: 1073741824]:
c.2_4 = c;
if (c.2_4 != 0)
goto <bb 3>; [89.00%]
else
goto <bb 5>; [11.00%]
<bb 5> [local count: 236223200]:
h = &p;
_5 = p[0];
if (_5 != 0)
goto <bb 6>; [50.00%]
else
goto <bb 7>; [50.00%]
<bb 6> [local count: 118111600]:
h = &j;
<bb 7> [local count: 236223200]:
e = 0;
j ={v} {CLOBBER};
l ={v} {CLOBBER};
k ={v} {CLOBBER};
n ={v} {CLOBBER};
p ={v} {CLOBBER};
return;
}
so it indeed has larger arrays. k is initialized but never used (so it is
missed DSE). n is used in stupid way:
h = &n;
_1 = n[0];
where h is write only static var, but we do not know that during early opts (we
could try our luck and schedule one extra writeonly detection before early
optimization passes, but I am not sure it is worth).
I would say that main issue is also missed DSE
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100314
[Bug 100314] missed optimization for dead code elimination at -O3 (vs. -O1)
(inlining differences due to missed dse)
