Linaro GCC Tracking

  1. Bug #689887
  2. Comment #26

Comment 26 for bug 689887

Revision history for this message
In , Mikpe (mikpe) wrote :

Created attachment 24503
more reduced test case, ICEs at -O1 for armv5te and armv6

Using this slightly more reduced test case I've found that gcc transforms

(set (reg:CC_NCV ...) (compare:CC_NCV (reg:DI ...) (const_int 1 ...)))
(if_then_else (ge (reg:CC_NCV ...) ...) ...)

to

(set (reg:CC_NCV ...) (compare:CC_NCV (reg:DI ...) (const_int 0 ...)))
(if_then_else (gt (reg:CC_NCV ...) ...)

because ifcvt calls noce_get_condition which calls canonicalize_condition, and the latter has a general rule to transform (GE x const) to (GT x const-1).

So the careful code in e.g. cbranchdi4 to not generate unimplemented comparisons is neutralized by generic code.

Do DImode comparisons really have to be asymmetric? I.e., could CC_NCV be removed? I see that LT is apparently supported so why can't GT be too?