[Bug tree-optimization/35292] Missing Const Prop -- union fields

[rguenth at gcc dot gnu dot org]

------- Comment #5 from rguenth at gcc dot gnu dot org  2009-05-23 09:23 -------
Hm, with my fix for PR36327 there is now a natural place to do this in SCCVN.
The question is how to properly get to the desired value.  We have (bit
access ranges):

 c.[0..31] = 20;

 ... = c.[0..7];
 ... = c.[8..15];

(or others depending on byte-order).  Ideally we can translate this by
using a BIT_FIELD_REF on the value stored - at least if both stored value
and read value are integral types.  For other type mixes proper
VIEW_CONVERT_EXPRs need to be done.  The question is if it is worth it
for non-constants.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35292