First off one of the questions just me being curious but
second is quite serious. Note, this is GIMPLE coming
into my optimization and not something I've modified.
Here's the C code:
type_t *
do_comp( type_t *data, size_t len)
{
type_t *res;
type_t *x = min_of_x( data, len);
type_t *y = max_of_y( data, len);
res = y;
if ( x < y ) res = 0;
return res;
}
And here's the resulting GIMPLE:
;; Function do_comp.constprop (do_comp.constprop.0, funcdef_no=5,
decl_uid=4392, cgraph_uid=3, symbol_order=68) (executed once)
do_comp.constprop (struct type_t * data)
{
struct type_t * res;
struct type_t * x;
struct type_t * y;
size_t len;
<bb 5> [local count: 1073741824]:
<bb 2> [local count: 1073741824]:
x_2 = min_of_x (data_1(D), 10000);
y_3 = max_of_y (data_1(D), 10000);
if (x_2 < y_3)
goto <bb 3>; [29.00%]
else
goto <bb 4>; [71.00%]
<bb 3> [local count: 311385128]:
<bb 4> [local count: 1073741824]:
# res_4 = PHI <y_3(2), 0B(3)>
return res_4;
}
The silly question first. In the "if" stmt how does GCC
get those probabilities? Which it shows as 29.00% and
71.00%. I believe they should both be 50.00%.
The serious question is what is going on with this phi?
res_4 = PHI <y_3(2), 0B(3)>
This makes zero sense practicality wise to me and how is
it supposed to be recognized and used? Note, I really do
need to transform the "0B" into something else for my
structure reorganization optimization.
Thanks,
Gary Oblock
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