[rfc] and [autovect patch] Vectorize reduction.

[Diego Novillo]

Richard Henderson wrote:

>>(f) I'm using replace_immediate_uses to replaces uses of a_3 in [Example1]
>>with uses of a_5 [Example2]. Is there a better way around this? (is there a
>>way to replace the defining stmt of an ssa-name with a new defining stmt
>>(for the same ssa-name), removing the original defining stmt?
> 
> 
> I'm not sure, but wouldn't it just be modifying SSA_NAME_DEF_STMT?  Diego?
> 
In theory, yes.  IIRC, we don't cache the defining statement of SSA 
names anywhere, so things shouldn't break.  But this sounds hacky.

Dorit, what are you trying to do?  Replace some SSA names with newly 
created names?  There is an update_ssa call in tree-cleanup-branch and a 
similar mechanism in ssaupdate-branch.

Zdenek and I are working on an SSA update mechanism along those lines. 
(http://gcc.gnu.org/ml/gcc-patches/2005-02/msg00187.html)


Diego.