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Re: Projects for beginners
- To: Richard Henderson <rth at redhat dot com>
- Subject: Re: Projects for beginners
- From: Daniel Berlin <dberlin at redhat dot com>
- Date: Wed, 31 Jan 2001 22:16:44 -0500 (EST)
- cc: Michael Meissner <meissner at cygnus dot com>, Daniel Berlin <dberlin at redhat dot com>, Zack Weinberg <zackw at Stanford dot EDU>, <gcc at gcc dot gnu dot org>
On Wed, 31 Jan 2001, Richard Henderson wrote:
> On Wed, Jan 31, 2001 at 08:15:22PM -0500, Michael Meissner wrote:
> > What it doesn't handle is a parallel that has two sets,
> > which on the x86 is for setting the condition code register.
>
> Those don't get created until combine.
>
> No, the real problem is that gcse doesn't handle hard registers,
> so the clobber of hard register 17 (flags) squelches everything.
>
The comment above hash_scan_insn claims it doesn't handle clobbers in
parallels, yet the code appears to.
Has anyone actually written down the work taken to create a mid level rtl,
and do lowering (maybe right before combine) on it?
And how much would it really buy us?
If someone gave a list of incremental steps to take to make it a reality,
it would make it much easier for people with spare time to do it.
--Dan