https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104639
Aldy Hernandez <aldyh at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |amacleod at redhat dot com
--- Comment #7 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
FWIW, thread2 does thread everything that is threadable. That is, we thread
5->3->4 from this:
<bb 3> [local count: 1073741824]:
# i_1 = PHI <i_2(D)(2), 6(5)>
if (i_1 == 4)
goto <bb 5>; [89.00%]
else
goto <bb 4>; [11.00%]
<bb 5> [local count: 955630224]:
goto <bb 3>; [100.00%]
into this:
<bb 2> [local count: 118111600]:
if (i_2(D) == 4)
goto <bb 3>; [97.00%]
else
goto <bb 4>; [3.00%]
<bb 3> [local count: 955630224]:
# i_5 = PHI <6(2)>
<bb 4> [local count: 118111600]:
# i_6 = PHI <i_2(D)(2), i_5(3)>
_3 = i_6 != 0;
return _3;
There are no more conditionals we can thread in the final form above.
To my untrained eye, it does seem like phiopt should be able to optimize:
<bb 4> [local count: 118111600]:
# i_6 = PHI <i_2(D)(2), 6(3)>
_3 = i_6 != 0;
into:
_3 = i_2 != 0;
Then BB2 and BB3 can just be cleaned up as dead?
