[Mesa-dev] [PATCH 5/7] i965/fs: Don't renumber UNIFORM registers.
Pohjolainen, Topi
topi.pohjolainen at intel.com
Fri Mar 14 03:40:28 PDT 2014
On Wed, Mar 12, 2014 at 11:56:05PM -0700, Kenneth Graunke wrote:
> On 03/12/2014 03:14 AM, Pohjolainen, Topi wrote:
> > On Tue, Mar 11, 2014 at 11:48:54PM -0700, Kenneth Graunke wrote:
> >> Previously, remove_dead_constants() would renumber the UNIFORM registers
> >> to be sequential starting from zero, and the resulting register number
> >> would be used directly as an index into the params[] array.
> >>
> >> This renumbering made it difficult to collect and save information about
> >> pull constant locations, since setup_pull_constants() and
> >> move_uniform_array_access_to_pull_constants() used different names.
> >>
> >> This patch generalizes setup_pull_constants() to decide whether each
> >> uniform register should be a pull constant, push constant, or neither
> >> (because it's unused). Then, it stores mappings from UNIFORM register
> >> numbers to params[] or pull_params[] indices in the push_constant_loc
> >> and pull_constant_loc arrays. (We already did this for pull constants.)
> >>
> >> Then, assign_curb_setup() just needs to consult the push_constant_loc
> >> array to get the real index into the params[] array.
> >>
> >> This effectively folds all the remove_dead_constants() functionality
> >> into assign_constant_locations(), while being less irritable to work
> >> with.
> >>
> >> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> >> ---
> >> src/mesa/drivers/dri/i965/brw_fs.cpp | 187 +++++++++++----------------
> >> src/mesa/drivers/dri/i965/brw_fs.h | 13 +-
> >> src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 3 +-
> >> 3 files changed, 85 insertions(+), 118 deletions(-)
> >>
> >> diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
> >> index 3c8237a..5e01e78 100644
> >> --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
> >> +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
> >> @@ -885,8 +885,8 @@ fs_visitor::import_uniforms(fs_visitor *v)
> >> hash_table_call_foreach(v->variable_ht,
> >> import_uniforms_callback,
> >> variable_ht);
> >> - this->params_remap = v->params_remap;
> >> - this->nr_params_remap = v->nr_params_remap;
> >> + this->push_constant_loc = v->push_constant_loc;
> >> + this->uniforms = v->uniforms;
> >> }
> >>
> >> /* Our support for uniforms is piggy-backed on the struct
> >> @@ -1397,11 +1397,8 @@ fs_visitor::assign_curb_setup()
> >> {
> >> if (dispatch_width == 8) {
> >> c->prog_data.first_curbe_grf = c->nr_payload_regs;
> >> - stage_prog_data->nr_params = uniforms;
> >> } else {
> >> c->prog_data.first_curbe_grf_16 = c->nr_payload_regs;
> >> - /* Make sure we didn't try to sneak in an extra uniform */
> >> - assert(uniforms == 0);
> >> }
> >>
> >> c->prog_data.curb_read_length = ALIGN(stage_prog_data->nr_params, 8) / 8;
> >> @@ -1412,7 +1409,19 @@ fs_visitor::assign_curb_setup()
> >>
> >> for (unsigned int i = 0; i < 3; i++) {
> >> if (inst->src[i].file == UNIFORM) {
> >> - int constant_nr = inst->src[i].reg + inst->src[i].reg_offset;
> >> + int uniform_nr = inst->src[i].reg + inst->src[i].reg_offset;
> >> + int constant_nr;
> >> + if (uniform_nr >= 0 && uniform_nr < (int) uniforms) {
> >> + constant_nr = push_constant_loc[uniform_nr];
> >> + } else {
> >> + /* Section 5.11 of the OpenGL 4.1 spec says:
> >> + * "Out-of-bounds reads return undefined values, which include
> >> + * values from other variables of the active program or zero."
> >> + * Just return the first push constant.
> >> + */
> >> + constant_nr = 0;
> >> + }
> >> +
> >> struct brw_reg brw_reg = brw_vec1_grf(c->nr_payload_regs +
> >> constant_nr / 8,
> >> constant_nr % 8);
> >> @@ -1724,94 +1733,6 @@ fs_visitor::compact_virtual_grfs()
> >> }
> >> }
> >>
> >> -bool
> >> -fs_visitor::remove_dead_constants()
> >> -{
> >> - if (dispatch_width == 8) {
> >> - this->params_remap = ralloc_array(mem_ctx, int, uniforms);
> >> - this->nr_params_remap = uniforms;
> >> -
> >> - for (unsigned int i = 0; i < uniforms; i++)
> >> - this->params_remap[i] = -1;
> >> -
> >> - /* Find which params are still in use. */
> >> - foreach_list(node, &this->instructions) {
> >> - fs_inst *inst = (fs_inst *)node;
> >> -
> >> - for (int i = 0; i < 3; i++) {
> >> - int constant_nr = inst->src[i].reg + inst->src[i].reg_offset;
> >> -
> >> - if (inst->src[i].file != UNIFORM)
> >> - continue;
> >> -
> >> - /* Section 5.11 of the OpenGL 4.3 spec says:
> >> - *
> >> - * "Out-of-bounds reads return undefined values, which include
> >> - * values from other variables of the active program or zero."
> >> - */
> >> - if (constant_nr < 0 || constant_nr >= (int)uniforms) {
> >> - constant_nr = 0;
> >> - }
> >> -
> >> - /* For now, set this to non-negative. We'll give it the
> >> - * actual new number in a moment, in order to keep the
> >> - * register numbers nicely ordered.
> >> - */
> >> - this->params_remap[constant_nr] = 0;
> >> - }
> >> - }
> >> -
> >> - /* Figure out what the new numbers for the params will be. At some
> >> - * point when we're doing uniform array access, we're going to want
> >> - * to keep the distinction between .reg and .reg_offset, but for
> >> - * now we don't care.
> >> - */
> >> - unsigned int new_nr_params = 0;
> >> - for (unsigned int i = 0; i < uniforms; i++) {
> >> - if (this->params_remap[i] != -1) {
> >> - this->params_remap[i] = new_nr_params++;
> >> - }
> >> - }
> >> -
> >> - /* Update the list of params to be uploaded to match our new numbering. */
> >> - for (unsigned int i = 0; i < uniforms; i++) {
> >> - int remapped = this->params_remap[i];
> >> -
> >> - if (remapped == -1)
> >> - continue;
> >> -
> >> - stage_prog_data->param[remapped] = stage_prog_data->param[i];
> >> - }
> >> -
> >> - uniforms = new_nr_params;
> >> - } else {
> >> - /* This should have been generated in the SIMD8 pass already. */
> >> - assert(this->params_remap);
> >> - }
> >> -
> >> - /* Now do the renumbering of the shader to remove unused params. */
> >> - foreach_list(node, &this->instructions) {
> >> - fs_inst *inst = (fs_inst *)node;
> >> -
> >> - for (int i = 0; i < 3; i++) {
> >> - int constant_nr = inst->src[i].reg + inst->src[i].reg_offset;
> >> -
> >> - if (inst->src[i].file != UNIFORM)
> >> - continue;
> >> -
> >> - /* as above alias to 0 */
> >> - if (constant_nr < 0 || constant_nr >= (int)this->nr_params_remap) {
> >> - constant_nr = 0;
> >> - }
> >> - assert(this->params_remap[constant_nr] != -1);
> >> - inst->src[i].reg = this->params_remap[constant_nr];
> >> - inst->src[i].reg_offset = 0;
> >> - }
> >> - }
> >> -
> >> - return true;
> >> -}
> >> -
> >> /*
> >> * Implements array access of uniforms by inserting a
> >> * PULL_CONSTANT_LOAD instruction.
> >> @@ -1872,8 +1793,7 @@ fs_visitor::move_uniform_array_access_to_pull_constants()
> >> }
> >>
> >> /**
> >> - * Choose accesses from the UNIFORM file to demote to using the pull
> >> - * constant buffer.
> >> + * Assign UNIFORM file registers to either push constants or pull constants.
> >> *
> >> * We allow a fragment shader to have more than the specified minimum
> >> * maximum number of fragment shader uniform components (64). If
> >> @@ -1882,24 +1802,62 @@ fs_visitor::move_uniform_array_access_to_pull_constants()
> >> * update the program to load them.
> >> */
> >> void
> >> -fs_visitor::setup_pull_constants()
> >> +fs_visitor::assign_constant_locations()
> >> {
> >> - /* Only allow 16 registers (128 uniform components) as push constants. */
> >> - unsigned int max_uniform_components = 16 * 8;
> >> - if (uniforms <= max_uniform_components)
> >> + /* Only the first compile (SIMD8 mode) gets to decide on locations. */
> >> + if (dispatch_width != 8)
> >> return;
> >>
> >> - /* Just demote the end of the list. We could probably do better
> >> + /* Find which UNIFORM registers are still in use. */
> >> + bool is_live[uniforms];
> >> + for (unsigned int i = 0; i < uniforms; i++) {
> >> + is_live[i] = false;
> >> + }
> >> +
> >> + foreach_list(node, &this->instructions) {
> >> + fs_inst *inst = (fs_inst *) node;
> >> +
> >> + for (int i = 0; i < 3; i++) {
> >> + if (inst->src[i].file != UNIFORM)
> >> + continue;
> >> +
> >> + int constant_nr = inst->src[i].reg + inst->src[i].reg_offset;
> >> + if (constant_nr >= 0 && constant_nr < (int) uniforms)
> >> + is_live[constant_nr] = true;
> >> + }
> >> + }
> >> +
> >> + /* Only allow 16 registers (128 uniform components) as push constants.
> >> + *
> >> + * Just demote the end of the list. We could probably do better
> >> * here, demoting things that are rarely used in the program first.
> >> */
> >> - unsigned int pull_uniform_base = max_uniform_components;
> >> + unsigned int max_push_components = 16 * 8;
> >> + unsigned int num_push_constants = 0;
> >>
> >> + push_constant_loc = ralloc_array(mem_ctx, int, uniforms);
> >> pull_constant_loc = ralloc_array(mem_ctx, int, uniforms);
> >> + for (unsigned int i = 0; i < uniforms; i++)
> >> + pull_constant_loc[i] = -1;
> >> +
> >> for (unsigned int i = 0; i < uniforms; i++) {
> >> - if (i < pull_uniform_base) {
> >> - pull_constant_loc[i] = -1;
> >> + if (!is_live[i] || pull_constant_loc[i] != -1) {
> >
> > I started wondering when the second condition fires and by inspecting code not
> > visible in this patch it seems that it cannot. The loop addresses elements in
> > the "pull_constant_loc[]" in order and never beyond current index "i".
>
> You are correct. At this point, it should never trigger.
>
> It will be triggered after the next patch ("i965/fs: Use a single
> instance of the pull_constant_loc array."). I should have introduced it
> in that patch, rather than here.
>
> Would you like me to make that change?
I don't really see the added value, I'd leave it as is.
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