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broadcom/compiler: Emit uniform loops using uniform control flow

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Similarly to if statements, uniform loops are now emitted without
predication, using simple branches for breaks and continues. The
uniformity of the loop is determined by running the
nir_divergence_analysis pass.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7726>
This commit is contained in:
Arcady Goldmints-Orlov
2020-12-24 10:24:56 -06:00
committed by Marge Bot
parent 6643bdbd53
commit 79bde75131
3 changed files with 85 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

86
src/broadcom/compiler/nir_to_vir.c
View File

@@ -2774,8 +2774,6 @@ ntq_emit_intrinsic(struct v3d_compile *c, nir_intrinsic_instr *instr)
* XXX perf: Could we be using flpush/flpop somehow for our execution channel
* enabling?
*
* XXX perf: For uniform control flow, we should be able to skip c->execute
* handling entirely.
*/
static void
ntq_activate_execute_for_block(struct v3d_compile *c)
@@ -2823,9 +2821,13 @@ ntq_emit_uniform_if(struct v3d_compile *c, nir_if *if_stmt)
ntq_emit_cf_list(c, &if_stmt->then_list);
if (!empty_else_block) {
/* At the end of the THEN block, jump to ENDIF */
/* At the end of the THEN block, jump to ENDIF, unless
* the block ended in a break or continue.
*/
if (!c->cur_block->branch_emitted) {
vir_BRANCH(c, V3D_QPU_BRANCH_COND_ALWAYS);
vir_link_blocks(c->cur_block, after_block);
}
/* Emit the else block. */
vir_set_emit_block(c, else_block);
@@ -2932,7 +2934,7 @@ ntq_emit_if(struct v3d_compile *c, nir_if *nif)
bool was_in_control_flow = c->in_control_flow;
c->in_control_flow = true;
if (!vir_in_nonuniform_control_flow(c) &&
nir_src_is_dynamically_uniform(nif->condition)) {
!nir_src_is_divergent(nif->condition)) {
ntq_emit_uniform_if(c, nif);
} else {
ntq_emit_nonuniform_if(c, nif);
@@ -2959,7 +2961,34 @@ ntq_emit_jump(struct v3d_compile *c, nir_jump_instr *jump)
break;
case nir_jump_return:
unreachable("All returns shouold be lowered\n");
unreachable("All returns should be lowered\n");
break;
case nir_jump_halt:
case nir_jump_goto:
case nir_jump_goto_if:
unreachable("not supported\n");
break;
}
}
static void
ntq_emit_uniform_jump(struct v3d_compile *c, nir_jump_instr *jump)
{
switch (jump->type) {
case nir_jump_break:
vir_BRANCH(c, V3D_QPU_BRANCH_COND_ALWAYS);
vir_link_blocks(c->cur_block, c->loop_break_block);
c->cur_block->branch_emitted = true;
break;
case nir_jump_continue:
vir_BRANCH(c, V3D_QPU_BRANCH_COND_ALWAYS);
vir_link_blocks(c->cur_block, c->loop_cont_block);
c->cur_block->branch_emitted = true;
break;
case nir_jump_return:
unreachable("All returns should be lowered\n");
break;
case nir_jump_halt:
@@ -2995,7 +3024,10 @@ ntq_emit_instr(struct v3d_compile *c, nir_instr *instr)
break;
case nir_instr_type_jump:
if (vir_in_nonuniform_control_flow(c))
ntq_emit_jump(c, nir_instr_as_jump(instr));
else
ntq_emit_uniform_jump(c, nir_instr_as_jump(instr));
break;
default:
@@ -3017,20 +3049,14 @@ ntq_emit_block(struct v3d_compile *c, nir_block *block)
static void ntq_emit_cf_list(struct v3d_compile *c, struct exec_list *list);
static void
ntq_emit_loop(struct v3d_compile *c, nir_loop *loop)
ntq_emit_nonuniform_loop(struct v3d_compile *c, nir_loop *loop)
{
bool was_in_control_flow = c->in_control_flow;
c->in_control_flow = true;
bool was_uniform_control_flow = false;
if (!vir_in_nonuniform_control_flow(c)) {
c->execute = vir_MOV(c, vir_uniform_ui(c, 0));
was_uniform_control_flow = true;
}
struct qblock *save_loop_cont_block = c->loop_cont_block;
struct qblock *save_loop_break_block = c->loop_break_block;
c->loop_cont_block = vir_new_block(c);
c->loop_break_block = vir_new_block(c);
@@ -3067,6 +3093,42 @@ ntq_emit_loop(struct v3d_compile *c, nir_loop *loop)
c->execute = c->undef;
else
ntq_activate_execute_for_block(c);
}
static void
ntq_emit_uniform_loop(struct v3d_compile *c, nir_loop *loop)
{
c->loop_cont_block = vir_new_block(c);
c->loop_break_block = vir_new_block(c);
vir_link_blocks(c->cur_block, c->loop_cont_block);
vir_set_emit_block(c, c->loop_cont_block);
ntq_emit_cf_list(c, &loop->body);
if (!c->cur_block->branch_emitted) {
vir_BRANCH(c, V3D_QPU_BRANCH_COND_ALWAYS);
vir_link_blocks(c->cur_block, c->loop_cont_block);
}
vir_set_emit_block(c, c->loop_break_block);
}
static void
ntq_emit_loop(struct v3d_compile *c, nir_loop *loop)
{
bool was_in_control_flow = c->in_control_flow;
c->in_control_flow = true;
struct qblock *save_loop_cont_block = c->loop_cont_block;
struct qblock *save_loop_break_block = c->loop_break_block;
if (vir_in_nonuniform_control_flow(c) || loop->divergent) {
ntq_emit_nonuniform_loop(c, loop);
} else {
ntq_emit_uniform_loop(c, loop);
}
c->loop_break_block = save_loop_break_block;
c->loop_cont_block = save_loop_cont_block;

6
src/broadcom/compiler/v3d_compiler.h
View File

@@ -456,6 +456,12 @@ struct qblock {
/** Offset within the uniform stream of the branch instruction */
uint32_t branch_uniform;
/**
* Has the terminating branch of this block already been emitted
* by a break or continue?
*/
bool branch_emitted;
/** @{ used by v3d_vir_live_variables.c */
BITSET_WORD *def;
BITSET_WORD *defin;

2
src/broadcom/compiler/vir.c
View File

@@ -1156,6 +1156,8 @@ v3d_attempt_compile(struct v3d_compile *c)
}
NIR_PASS_V(c->s, nir_lower_bool_to_int32);
nir_convert_to_lcssa(c->s, true, true);
NIR_PASS_V(c->s, nir_divergence_analysis);
NIR_PASS_V(c->s, nir_convert_from_ssa, true);
struct nir_schedule_options schedule_options = {