On Fri, May 27, 2016 at 7:06 PM, Francisco Jerez <curroje...@riseup.net>
wrote:
> This requires using a bitset instead of a boolean flag to keep track
> of the GRFs we've seen a generating instruction for already. The
> search loop continues until all instructions initializing the value of
> the source VGRF have been found, or it is determined that coalescing
> is not possible.
> ---
> src/mesa/drivers/dri/i965/brw_fs.cpp | 46
> ++++++++++++++++++++++++++++--------
> 1 file changed, 36 insertions(+), 10 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp
> b/src/mesa/drivers/dri/i965/brw_fs.cpp
> index 4062ea2..50552cb 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
> @@ -2782,6 +2782,20 @@ fs_visitor::opt_redundant_discard_jumps()
> return progress;
> }
>
> +/**
> + * Compute a bitmask with GRF granularity with a bit set for each GRF
> starting
> + * from \p r which overlaps the region starting at \p r and spanning \p n
> GRF
> + * units.
> + */
> +static inline unsigned
> +mask_relative_to(const fs_reg &r, const fs_reg &s, unsigned n)
> +{
> + const int rel_offset = (reg_offset(s) - reg_offset(r)) / REG_SIZE;
> + assert(reg_space(r) == reg_space(s) &&
> + rel_offset >= 0 && rel_offset < int(8 * sizeof(unsigned)));
>
Isn't that rel_offset < REG_SIZE? Or do you mean "unsigned-many bits?
> + return ((1 << n) - 1) << rel_offset;
> +}
> +
> bool
> fs_visitor::compute_to_mrf()
> {
> @@ -2813,10 +2827,12 @@ fs_visitor::compute_to_mrf()
> if (this->virtual_grf_end[inst->src[0].nr] > ip)
> continue;
>
> - /* Found a move of a GRF to a MRF. Let's see if we can go
> - * rewrite the thing that made this GRF to write into the MRF.
> + /* Found a move of a GRF to a MRF. Let's see if we can go rewrite
> the
> + * things that computed the value of all GRFs of the source
> region. The
> + * regs_left bitset keeps track of the registers we haven't yet
> found a
> + * generating instruction for.
> */
> - bool found = false;
> + unsigned regs_left = (1 << inst->regs_read(0)) - 1;
>
> foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst,
> inst) {
> if (regions_overlap(scan_inst->dst, scan_inst->regs_written *
> REG_SIZE,
> @@ -2855,10 +2871,11 @@ fs_visitor::compute_to_mrf()
> }
> }
>
> - if (scan_inst->dst.reg_offset == inst->src[0].reg_offset)
> - found = true;
> -
> - break;
> + /* Clear the bits for any registers this instruction
> overwrites. */
> + regs_left &= ~mask_relative_to(
> + inst->src[0], scan_inst->dst, scan_inst->regs_written);
> + if (!regs_left)
> + break;
>
}
>
> /* We don't handle control flow here. Most computation of
> @@ -2901,14 +2918,21 @@ fs_visitor::compute_to_mrf()
> }
> }
>
> - if (!found)
> + if (regs_left)
> continue;
>
> - /* Found all generating instructions of our MRF's source value.
> + /* Found all generating instructions of our MRF's source value, so
> it
> + * should be safe to rewrite them to point to the MRF directly.
> */
> + regs_left = (1 << inst->regs_read(0)) - 1;
> +
> foreach_inst_in_block_reverse_starting_from(fs_inst, scan_inst,
> inst) {
> if (regions_overlap(scan_inst->dst, scan_inst->regs_written *
> REG_SIZE,
> inst->src[0], inst->regs_read(0) *
> REG_SIZE)) {
> + /* Clear the bits for any registers this instruction
> overwrites. */
> + regs_left &= ~mask_relative_to(
> + inst->src[0], scan_inst->dst, scan_inst->regs_written);
> +
> const unsigned rel_offset = (reg_offset(scan_inst->dst) -
> reg_offset(inst->src[0])) /
> REG_SIZE;
>
> @@ -2935,10 +2959,12 @@ fs_visitor::compute_to_mrf()
> scan_inst->dst.file = MRF;
> scan_inst->dst.reg_offset = 0;
> scan_inst->saturate |= inst->saturate;
> - break;
> + if (!regs_left)
> + break;
> }
> }
>
> + assert(!regs_left);
> inst->remove(block);
> progress = true;
> }
> --
> 2.7.3
>
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