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aco: add struct and helpers for exec potentially empty

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Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30320>
This commit is contained in:
Rhys Perry
2024-07-19 19:54:57 +01:00
committed by Marge Bot
parent 39264a90c3
commit a8a15dc5b5
2 changed files with 76 additions and 87 deletions
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125
src/amd/compiler/aco_instruction_selection.cpp
View File

@@ -54,15 +54,11 @@ struct if_context {
Temp cond;
bool divergent_old;
bool exec_potentially_empty_discard_old;
bool exec_potentially_empty_break_old;
bool exec_potentially_empty_continue_old;
bool had_divergent_discard_old;
bool had_divergent_discard_then;
bool has_divergent_continue_old;
bool has_divergent_continue_then;
uint16_t exec_potentially_empty_break_depth_old;
uint16_t exec_potentially_empty_continue_depth_old;
struct exec_info exec_old;
unsigned BB_if_idx;
unsigned invert_idx;
@@ -9099,7 +9095,7 @@ visit_intrinsic(isel_context* ctx, nir_intrinsic_instr* instr)
bld.pseudo(aco_opcode::p_demote_to_helper, cond);
if (ctx->block->loop_nest_depth || ctx->cf_info.parent_if.is_divergent)
ctx->cf_info.exec_potentially_empty_discard = true;
ctx->cf_info.exec.potentially_empty_discard = true;
ctx->block->kind |= block_kind_uses_discard;
ctx->program->needs_exact = true;
@@ -9125,7 +9121,7 @@ visit_intrinsic(isel_context* ctx, nir_intrinsic_instr* instr)
bld.pseudo(aco_opcode::p_discard_if, cond);
if (ctx->block->loop_nest_depth || ctx->cf_info.parent_if.is_divergent)
ctx->cf_info.exec_potentially_empty_discard = true;
ctx->cf_info.exec.potentially_empty_discard = true;
ctx->cf_info.had_divergent_discard |= in_exec_divergent_or_in_loop(ctx);
ctx->block->kind |= block_kind_uses_discard;
ctx->program->needs_exact = true;
@@ -10251,7 +10247,7 @@ visit_undef(isel_context* ctx, nir_undef_instr* instr)
void
begin_loop(isel_context* ctx, loop_context* lc)
{
// TODO: we might want to wrap the loop around a branch if exec_potentially_empty=true
// TODO: we might want to wrap the loop around a branch if exec.potentially_empty=true
append_logical_end(ctx->block);
ctx->block->kind |= block_kind_loop_preheader | block_kind_uniform;
Builder bld(ctx->program, ctx->block);
@@ -10276,6 +10272,32 @@ begin_loop(isel_context* ctx, loop_context* lc)
lc->divergent_if_old = std::exchange(ctx->cf_info.parent_if.is_divergent, false);
}
void
update_exec_info(isel_context* ctx)
{
if (!ctx->block->loop_nest_depth && !ctx->cf_info.parent_if.is_divergent)
ctx->cf_info.exec.potentially_empty_discard = false;
ctx->cf_info.exec.potentially_empty_break &=
ctx->block->loop_nest_depth >= ctx->cf_info.exec.potentially_empty_break_depth;
ctx->cf_info.exec.potentially_empty_continue &=
ctx->block->loop_nest_depth >= ctx->cf_info.exec.potentially_empty_continue_depth;
if (ctx->block->loop_nest_depth == ctx->cf_info.exec.potentially_empty_break_depth &&
!ctx->cf_info.parent_if.is_divergent && !ctx->cf_info.parent_loop.has_divergent_continue) {
ctx->cf_info.exec.potentially_empty_break = false;
}
if (ctx->block->loop_nest_depth == ctx->cf_info.exec.potentially_empty_continue_depth &&
!ctx->cf_info.parent_if.is_divergent) {
ctx->cf_info.exec.potentially_empty_continue = false;
}
if (!ctx->cf_info.exec.potentially_empty_break)
ctx->cf_info.exec.potentially_empty_break_depth = UINT16_MAX;
if (!ctx->cf_info.exec.potentially_empty_continue)
ctx->cf_info.exec.potentially_empty_continue_depth = UINT16_MAX;
}
void
end_loop(isel_context* ctx, loop_context* lc)
{
@@ -10286,14 +10308,14 @@ end_loop(isel_context* ctx, loop_context* lc)
Builder bld(ctx->program, ctx->block);
append_logical_end(ctx->block);
/* No need to check exec_potentially_empty_break/continue originating inside the loop. In the
/* No need to check exec.potentially_empty_break/continue originating inside the loop. In the
* only case where it's possible at this point (divergent break after divergent continue), we
* should continue anyway. */
if (ctx->cf_info.exec_potentially_empty_discard ||
(ctx->cf_info.exec_potentially_empty_break &&
ctx->cf_info.exec_potentially_empty_break_depth < ctx->block->loop_nest_depth) ||
(ctx->cf_info.exec_potentially_empty_continue &&
ctx->cf_info.exec_potentially_empty_continue_depth < ctx->block->loop_nest_depth)) {
if (ctx->cf_info.exec.potentially_empty_discard ||
(ctx->cf_info.exec.potentially_empty_break &&
ctx->cf_info.exec.potentially_empty_break_depth < ctx->block->loop_nest_depth) ||
(ctx->cf_info.exec.potentially_empty_continue &&
ctx->cf_info.exec.potentially_empty_continue_depth < ctx->block->loop_nest_depth)) {
/* Discards can result in code running with an empty exec mask.
* This would result in divergent breaks not ever being taken. As a
* workaround, break the loop when the loop mask is empty instead of
@@ -10343,12 +10365,7 @@ end_loop(isel_context* ctx, loop_context* lc)
ctx->cf_info.parent_loop.has_divergent_continue = lc->divergent_cont_old;
ctx->cf_info.parent_loop.has_divergent_branch = lc->divergent_branch_old;
ctx->cf_info.parent_if.is_divergent = lc->divergent_if_old;
if (!ctx->block->loop_nest_depth && !ctx->cf_info.parent_if.is_divergent)
ctx->cf_info.exec_potentially_empty_discard = false;
if (ctx->block->loop_nest_depth < ctx->cf_info.exec_potentially_empty_break_depth) {
ctx->cf_info.exec_potentially_empty_break = false;
ctx->cf_info.exec_potentially_empty_break_depth = UINT16_MAX;
}
update_exec_info(ctx);
}
void
@@ -10375,9 +10392,9 @@ emit_loop_jump(isel_context* ctx, bool is_break)
}
ctx->cf_info.parent_loop.has_divergent_branch = true;
if (!ctx->cf_info.exec_potentially_empty_break) {
ctx->cf_info.exec_potentially_empty_break = true;
ctx->cf_info.exec_potentially_empty_break_depth = ctx->block->loop_nest_depth;
if (!ctx->cf_info.exec.potentially_empty_break) {
ctx->cf_info.exec.potentially_empty_break = true;
ctx->cf_info.exec.potentially_empty_break_depth = ctx->block->loop_nest_depth;
}
} else {
logical_target = &ctx->program->blocks[ctx->cf_info.parent_loop.header_idx];
@@ -10398,9 +10415,9 @@ emit_loop_jump(isel_context* ctx, bool is_break)
ctx->cf_info.parent_loop.has_divergent_continue = true;
ctx->cf_info.parent_loop.has_divergent_branch = true;
if (!ctx->cf_info.exec_potentially_empty_continue) {
ctx->cf_info.exec_potentially_empty_continue = true;
ctx->cf_info.exec_potentially_empty_continue_depth = ctx->block->loop_nest_depth;
if (!ctx->cf_info.exec.potentially_empty_continue) {
ctx->cf_info.exec.potentially_empty_continue = true;
ctx->cf_info.exec.potentially_empty_continue_depth = ctx->block->loop_nest_depth;
}
}
@@ -10610,22 +10627,13 @@ begin_divergent_if_then(isel_context* ctx, if_context* ic, Temp cond,
ic->BB_endif = Block();
ic->BB_endif.kind |= (block_kind_merge | (ctx->block->kind & block_kind_top_level));
ic->exec_potentially_empty_discard_old = ctx->cf_info.exec_potentially_empty_discard;
ic->exec_potentially_empty_break_old = ctx->cf_info.exec_potentially_empty_break;
ic->exec_potentially_empty_continue_old = ctx->cf_info.exec_potentially_empty_continue;
ic->exec_potentially_empty_break_depth_old = ctx->cf_info.exec_potentially_empty_break_depth;
ic->exec_potentially_empty_continue_depth_old =
ctx->cf_info.exec_potentially_empty_continue_depth;
ic->exec_old = ctx->cf_info.exec;
ic->divergent_old = ctx->cf_info.parent_if.is_divergent;
ic->had_divergent_discard_old = ctx->cf_info.had_divergent_discard;
ctx->cf_info.parent_if.is_divergent = true;
/* divergent branches use cbranch_execz */
ctx->cf_info.exec_potentially_empty_discard = false;
ctx->cf_info.exec_potentially_empty_break = false;
ctx->cf_info.exec_potentially_empty_break_depth = UINT16_MAX;
ctx->cf_info.exec_potentially_empty_continue = false;
ctx->cf_info.exec_potentially_empty_continue_depth = UINT16_MAX;
ctx->cf_info.exec = exec_info();
/** emit logical then block */
ctx->program->next_divergent_if_logical_depth++;
@@ -10676,20 +10684,9 @@ begin_divergent_if_else(isel_context* ctx, if_context* ic,
sel_ctrl == nir_selection_control_divergent_always_taken;
ctx->block->instructions.push_back(std::move(branch));
ic->exec_potentially_empty_discard_old |= ctx->cf_info.exec_potentially_empty_discard;
ic->exec_potentially_empty_break_old |= ctx->cf_info.exec_potentially_empty_break;
ic->exec_potentially_empty_break_depth_old = std::min(
ic->exec_potentially_empty_break_depth_old, ctx->cf_info.exec_potentially_empty_break_depth);
ic->exec_potentially_empty_continue_old |= ctx->cf_info.exec_potentially_empty_continue;
ic->exec_potentially_empty_continue_depth_old =
std::min(ic->exec_potentially_empty_continue_depth_old,
ctx->cf_info.exec_potentially_empty_continue_depth);
ic->exec_old.combine(ctx->cf_info.exec);
/* divergent branches use cbranch_execz */
ctx->cf_info.exec_potentially_empty_discard = false;
ctx->cf_info.exec_potentially_empty_break = false;
ctx->cf_info.exec_potentially_empty_break_depth = UINT16_MAX;
ctx->cf_info.exec_potentially_empty_continue = false;
ctx->cf_info.exec_potentially_empty_continue_depth = UINT16_MAX;
ctx->cf_info.exec = exec_info();
ic->had_divergent_discard_then = ctx->cf_info.had_divergent_discard;
ctx->cf_info.had_divergent_discard = ic->had_divergent_discard_old;
@@ -10739,32 +10736,8 @@ end_divergent_if(isel_context* ctx, if_context* ic)
append_logical_start(ctx->block);
ctx->cf_info.parent_if.is_divergent = ic->divergent_old;
ctx->cf_info.exec_potentially_empty_discard |= ic->exec_potentially_empty_discard_old;
ctx->cf_info.exec_potentially_empty_break |= ic->exec_potentially_empty_break_old;
ctx->cf_info.exec_potentially_empty_break_depth = std::min(
ic->exec_potentially_empty_break_depth_old, ctx->cf_info.exec_potentially_empty_break_depth);
ctx->cf_info.exec_potentially_empty_continue |= ic->exec_potentially_empty_continue_old;
ctx->cf_info.exec_potentially_empty_continue_depth =
std::min(ic->exec_potentially_empty_continue_depth_old,
ctx->cf_info.exec_potentially_empty_continue_depth);
if (ctx->block->loop_nest_depth == ctx->cf_info.exec_potentially_empty_break_depth &&
!ctx->cf_info.parent_if.is_divergent && !ctx->cf_info.parent_loop.has_divergent_continue) {
ctx->cf_info.exec_potentially_empty_break = false;
ctx->cf_info.exec_potentially_empty_break_depth = UINT16_MAX;
}
if (ctx->block->loop_nest_depth == ctx->cf_info.exec_potentially_empty_continue_depth &&
!ctx->cf_info.parent_if.is_divergent) {
ctx->cf_info.exec_potentially_empty_continue = false;
ctx->cf_info.exec_potentially_empty_continue_depth = UINT16_MAX;
}
/* uniform control flow never has an empty exec-mask */
if (!ctx->block->loop_nest_depth && !ctx->cf_info.parent_if.is_divergent) {
ctx->cf_info.exec_potentially_empty_discard = false;
ctx->cf_info.exec_potentially_empty_break = false;
ctx->cf_info.exec_potentially_empty_break_depth = UINT16_MAX;
ctx->cf_info.exec_potentially_empty_continue = false;
ctx->cf_info.exec_potentially_empty_continue_depth = UINT16_MAX;
}
ctx->cf_info.exec.combine(ic->exec_old);
update_exec_info(ctx);
ctx->cf_info.had_divergent_discard |= ic->had_divergent_discard_then;
/* We shouldn't create unreachable blocks. */

38
src/amd/compiler/aco_instruction_selection.h
View File

@@ -35,6 +35,31 @@ struct shader_io_state {
}
};
struct exec_info {
/* Set to false when loop_nest_depth==0 && parent_if.is_divergent==false */
bool potentially_empty_discard = false;
uint16_t potentially_empty_break_depth = UINT16_MAX;
/* Set to false when loop_nest_depth==exec_potentially_empty_break_depth,
* parent_if.is_divergent==false and parent_loop.has_divergent_continue==false. Also set to
* false if loop_nest_depth<exec_potentially_empty_break_depth. */
bool potentially_empty_break = false;
uint16_t potentially_empty_continue_depth = UINT16_MAX;
/* Set to false when loop_nest_depth==exec_potentially_empty_break_depth
* and parent_if.is_divergent==false. */
bool potentially_empty_continue = false;
void combine(struct exec_info& other)
{
potentially_empty_discard |= other.potentially_empty_discard;
potentially_empty_break_depth =
std::min(potentially_empty_break_depth, other.potentially_empty_break_depth);
potentially_empty_break |= other.potentially_empty_break;
potentially_empty_continue_depth =
std::min(potentially_empty_continue_depth, other.potentially_empty_continue_depth);
potentially_empty_continue |= other.potentially_empty_continue;
}
};
struct isel_context {
const struct aco_compiler_options* options;
const struct ac_shader_args* args;
@@ -58,17 +83,8 @@ struct isel_context {
bool is_divergent = false;
} parent_if;
bool had_divergent_discard = false;
bool exec_potentially_empty_discard =
false; /* set to false when loop_nest_depth==0 && parent_if.is_divergent==false */
uint16_t exec_potentially_empty_break_depth = UINT16_MAX;
/* Set to false when loop_nest_depth==exec_potentially_empty_break_depth,
* parent_if.is_divergent==false and parent_loop.has_divergent_continue==false. Also set to
* false if loop_nest_depth<exec_potentially_empty_break_depth */
bool exec_potentially_empty_break = false;
uint16_t exec_potentially_empty_continue_depth = UINT16_MAX;
/* Set to false when loop_nest_depth==exec_potentially_empty_break_depth
* and parent_if.is_divergent==false. */
bool exec_potentially_empty_continue = false;
struct exec_info exec;
} cf_info;
/* NIR range analysis. */