[Bug tree-optimization/45397] [4.5/4.6/4.7 Regression] Issues with integer narrowing conversions

["ktietz at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45397

Kai Tietz <ktietz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |ktietz at gcc dot gnu.org

--- Comment #6 from Kai Tietz <ktietz at gcc dot gnu.org> 2012-01-02 13:09:09 UTC ---
Hmm, we could solve this via forward-propagation in gimple, too.
I have a patch which does this, but not sure if it is material for current
stage.  The missing patterns in forward-propagation are:
  - X ==/!= X -> true/false,
  - (type) X ==/!= (type) X -> true/false
  - X code Y ==/!= X code Z -> Y ==/!= Z (with code +, -, or ^).
  - (type) X ==/!= Y & CST -> X ==/!= (type-of-X) (Y & CST) if type-of-X has
smaller, or equal precision as type and is unsigned, and type-of-x and type are
of integral kind,
  and CST fits into type-of-X.
  - (type) (X op CST) -> (type) X op CST' with CST' = (type) X; and type has
smaller or equal precision to type-of-x and both types are of integral kind.
(for op = +,-,&,|,^)
  - (type) ((type2) X op Y) -> X op (type) Y, if type has smaller or equal
precision to type2 and type-of-x is compatible to type, all types are of
integral kind, and op is a +,-,&,|,or ^ expression.