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Re: [PATCH 1/3] SH-2A FDPIC: New pattern: use_initial_val


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~


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