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Re: Help with implementing Wine optimization experiment


On Sun, Aug 14, 2016 at 01:23:16AM -0500, Daniel Santos wrote:
> I'm experimenting with ways to optimize wine (x86 target only) and I believe
> I can shrink wine's total text size by around 7% by outlining the lengthy
> pro- and epilogues required for ms_abi functions making sysv_abi calls.
> Theoretically, fewer instruction cache misses will offset the extra 4
> instructions per function and result in a net performance gain. However, I'm
> new to the gcc project and a novice x86 assembly programmer as well (have
> been wanting to work on gcc for a while now!) In short, I want to:
> 
> 1. Replace the prologue that pushes di, sp and xmm6-15 with a single call to
> a global "ms_abi_push_regs" routine
> 2. Replace the epilogue that pops these regs with a jmp to a global
> "ms_abi_pop_regs" routine
> 3. Add the two routines somewhere so that they are linked into the output.

I think you want to put those into libgcc then.

> 
> I have this working in a small-scale experiment (writing the ms_abi function
> in assembly), but I'm not certain how I would add these routines. Should I
> make them built-ins?
> 
> I have found the code that adds the clobber RTL instructions in
> ix86_expand_call() (gcc/config/i386/i386.c:25832), and I see that
> thread_prologue_and_epilogue_insns() (gcc/function.c) is where these
> clobbers are expanded into the prologue and epilogue, but I'm not sure what
> the cleanest way to convert this is. My thought was to replace the
> clobber_reg() calls with one that would add an insn_call, or would it be
> better to do this in thread_prologue_and_epilogue_insns() where prologue and
> epilogue generation belongs? But that function is for all targets. Any
> pointers greatly appreciated!

I think you probably want to look at ix86_expand_prologue.

 Hope that helps, but I'm no expert, so take it with some salt.

 Trev


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