http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60962
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Status|UNCONFIRMED |NEW
Last reconfirmed| |2014-04-25
CC| |rguenth at gcc dot gnu.org
Component|c++ |middle-end
Ever confirmed|0 |1
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
We retain + -2.f*point[] until RTL expansion where then somewhere following
we have special code expanding 2.f * point[] but not -2.f * point[].
Confirmed.
We should optimize A + -2.*B to A - 2. * B. I believe we did so at some
point in the past.
Looks like we do
case PLUS_EXPR:
/* A + (-B) -> A - B */
if (TREE_CODE (arg1) == NEGATE_EXPR
&& (flag_sanitize & SANITIZE_SI_OVERFLOW) == 0)
return fold_build2_loc (loc, MINUS_EXPR, type,
Which matches NEGATE_EXPR and doesn't use negate_expr_p for some reason
(and sanitize check w/o checking we are processing integer types ...)
But negate_expr_p has
case REAL_CST:
/* We want to canonicalize to positive real constants. Pretend
that only negative ones can be easily negated. */
return REAL_VALUE_NEGATIVE (TREE_REAL_CST (t));
