https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103281
--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Hmm:
# RANGE [irange] char [0, 2] NONZERO 0x3
c_9 = (charD.7) b.4_5;
_1 = c_9 <= 0;
Should _1 be replaced with c_9 == 0 which then can be simplified to b.4_5 == 0
That is PR 28794 I think.
And then after that we get:
b.4_5 == (unsigned int)(b.4_5 == 0)
Which should be optimized down to false though we don't either.
unsigned f(unsigned t)
{
unsigned a = t == 0;
return t == a;
}
The general CST cases (I hope I did these correctly):
a == (a == CST) ->
CST == 0 -> false
CST == 1 -> a == 1 | a == 0
others -> a == 0
a != (a == CST) ->
CST == 0: false
CST == 1: a != 0 || a != 1
others : a != 0
a != (a != CST) ->
CST == 0: a == 1 | a == 0
CST == 1: true
others : a != 1
a == (a != CST) ->
CST == 0: a == 1 | a == 0
CST == 1: false
others : a == 1
