https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102546
Aldy Hernandez <aldyh at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |aldyh at gcc dot gnu.org,
| |amacleod at redhat dot com
--- Comment #2 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
By VRP1 we seem to be calculating the following:
(f_8 << f_8) && (f_8 == 0)
This would fold to false, which would elide the foo():
<bb 7> [local count: 59055800]:
b = 0;
_3 = f_8 << f_8;
_4 = (char) _3;
_5 = (int) _4;
if (_4 > 0)
goto <bb 8>; [64.06%]
else
goto <bb 10>; [35.94%]
<bb 8> [local count: 34842922]:
if (f_8 == 0)
goto <bb 9>; [71.10%]
else
goto <bb 10>; [28.90%]
<bb 9> [local count: 12809203]:
foo ();
So from the outset, it seems like this is a missing relation in range-ops.
That is if we know f_8 << f_8 is non-zero, then we know f_8 cannot be 0. This
looks like an easy fix, however...
What I fail to see is how "a" got removed entirely from the IL, making this
scenario possible:
if (!(a >= d || f))
foo();
Am I missing something obvious here?
