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Re: [PATCH 1/3] SH-2A FDPIC: New pattern: use_initial_val
- From: Richard Henderson <rth at redhat dot com>
- To: Andrew Stubbs <ams at codesourcery dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Thu, 19 Aug 2010 11:18:06 -0700
- Subject: Re: [PATCH 1/3] SH-2A FDPIC: New pattern: use_initial_val
- References: <4C6D56F2.3060204@codesourcery.com>
On 08/19/2010 09:08 AM, Andrew Stubbs wrote:
> This patch creates a new instruction pattern "use_initial_val".
>
> The purpose of this patch is to allow late optimization passes to use
> re-use existing pseudo-registers, even if the use of the register has
> been optimized away in earlier passes.
What is a target intended to do in this use_initial_val pattern?
Looking forward to 3/3, it seems you emit a fancy USE insn, whose
purpose appears to be simply to extend the lifetime of the pseudo,
without actually using it in a specific pattern.
Without looking deeper, it seems this is a mistake.
Can you explain further when and why this is required?
r~