[tree-ssa] Lazy updating of stmt operands

[Diego Novillo]

On Sun, 2003-12-07 at 11:19, Zdenek Dvorak wrote:

> what is the purpose of having lists of stmt operands updated on demand?
>
Performance.  If the statement hasn't changed, no point re-scanning it.

> I thought that it is for performance reasons, but this seems not to be
> the case as all the statements are anyway scanned in the final dce pass,
> so they end up in updated forms and we cannot gain anything elsewhere.
> 
The call to get_stmt_operands doesn't necessarily mean that the
statement will be re-scanned.

> Why I am interested in this is that it prevents us from having also
> def-use edges (immediate uses) provided explicitly, which would be
> convenient in two cases I have encountered recently.
> 
tree-dfa.c:compute_immediate_uses()


Diego.