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Re: COND_EXPR lowering patch
- From: Andrew MacLeod <amacleod at redhat dot com>
- To: Jeff Law <law at redhat dot com>
- Cc: Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>, gcc mailing list <gcc at gcc dot gnu dot org>
- Date: 26 Aug 2003 14:41:49 -0400
- Subject: Re: COND_EXPR lowering patch
- References: <200308261831.h7QIV460004620@speedy.slc.redhat.com>
On Tue, 2003-08-26 at 14:31, law@redhat.com wrote:
>
> >I'd also be tempted to try to call that final DCE from within
> >SSA->Normal once we've eliminated PHIs, but before we've actually
> >written the program back to normal form... Then we could get everything
> >thats really dead at that point...
> We run DCE just before the conversion from SSA to normal form. I would not
> expect that SSA to normal exposes any dead code. Then again, I could be
> wrong.
>
It can expose dead control flow, plus anything which ripples from that,
but perhaps we get that later? We currently cant eliminate flow which
has a PHI node in the post dominator. SSA->Normal eliminates all the PHI
nodes, so these empty control structures become fair game if the
elements of the PHI node coalesced together and no code was inserted
into the empty control blocks....
Andrew