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Re: [PATCH] enable fdpic targets/emulations for sh*-*-linux*
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Oleg Endo <oleg dot endo at t-online dot de>
- Cc: Rich Felker <dalias at libc dot org>, binutils at sourceware dot org
- Date: Sun, 4 Oct 2015 03:42:20 -0500
- Subject: Re: [PATCH] enable fdpic targets/emulations for sh*-*-linux*
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On Sun, Oct 04, 2015 at 12:32:54PM +0900, Oleg Endo wrote:
> > I think we should focus on the big performance problem that would make
> > a much much bigger difference: very bad codegen by gcc. Aside from
> > lack of shrink-wrapping, poor hanling of the PIC register (like the
> > way x86 used to handle %ebx, as permanently-reserved and unusable)
> > stands out at something that needs to be fixed.
>
> Shrink wrapping is being done for all backends. In fact, it has been
> improved recently. Of course there could be some SH specific cases
> which aren't optimized well. Please open PRs in GCC's bugzilla for
> issues with the compiler.
If the prologue sets up a register that is used pretty much everywhere
(like a PIC register) we cannot shrink-wrap much. After shrink-wrapping
you always still have a single prologue (and epilogue).
Your problem might be different; I can't tell without examples.
Segher