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Re: Congerie of performance improvements, take two

On Wed, Feb 12, 2003 at 06:52:25PM -0800, Zack Weinberg wrote:
> This is a revised version of the patch I posted last night.  The
> changes are: (1) I didn't mess up the GTY markers, so it actually
> works; (2) I reordered the fields in the alist structure in i386.c to
> enable tail recursion; (3) I redid bfs_walk from scratch; it's now
> reentrant again, and even faster to boot.
> The changes to bfs_walk deserve a bit of explanation.  I eliminated
> the varray entirely, in favor of an open-coded circular queue.  (The
> older code just kept enlarging the varray forever, instead of reusing
> slots that were no longer holding live data.)  The initial storage for
> this queue is on the stack.  If it needs to grow past ten slots it
> gets moved to the malloc arena.  This never happens in my sp.ii test
> case, but does happen several times in the g++ test suite (so I'm
> confident there aren't bugs in the implementation).  Then, for
> additional savings, I put BINFO_BASETYPES pointers on the queue
> instead of unpacking their contents onto the queue.  This reduces the
> chance that the queue will need to grow.
> The upshot for sp.ii is a 2.67% performance improvement relative to
> current CVS, and a 0.31% improvement relative to the previous patch
> (these are "estimated cycles" as calculated by cachegrind).
> zw
>         * emit-rtl.c (init_emit): Use ggc_alloc for regno_reg_rtx.
>         * function.h (struct emit_status): Length of regno_pointer_align
>         and x_regno_reg_rtx as seen by gengtype is only x_reg_rtx_no,
>         not regno_pointer_align_length (i.e. length actually used, not
>         length as allocated)

Shouldn't then init_emit's
    = (unsigned char *) ggc_alloc_cleared (f->emit->regno_pointer_align_length
                                           * sizeof (unsigned char));
be replaced with:
    = (unsigned char *) ggc_alloc (f->emit->regno_pointer_align_length);
  memset (f->emit->regno_pointer_align, 0, LAST_VIRTUAL_REGISTER + 1);
and in gen_reg_rtx when reallocing the arrays both memset's removed?


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