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aco: set exec_potentially_empty after continues/breaks in nested IFs

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Fixes: 93c8ebfa ('aco: Initial commit of independent AMD compiler')
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/3257>
This commit is contained in:
Rhys Perry 2020-01-07 16:33:47 +00:00 • committed by Marge Bot
parent 4e83e05e62
commit 5ea23ba659
2 changed files with 51 additions and 15 deletions
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59
src/amd/compiler/aco_instruction_selection.cpp
View file

@ -71,7 +71,7 @@ public:
ctx->cf_info.parent_if.is_divergent = divergent_if_old;
ctx->cf_info.loop_nest_depth = ctx->cf_info.loop_nest_depth - 1;
if (!ctx->cf_info.loop_nest_depth && !ctx->cf_info.parent_if.is_divergent)
ctx->cf_info.exec_potentially_empty = false;
ctx->cf_info.exec_potentially_empty_discard = false;
}
};
@ -79,7 +79,9 @@ struct if_context {
Temp cond;
bool divergent_old;
bool exec_potentially_empty_old;
bool exec_potentially_empty_discard_old;
bool exec_potentially_empty_break_old;
uint16_t exec_potentially_empty_break_depth_old;
unsigned BB_if_idx;
unsigned invert_idx;
@ -3902,7 +3904,7 @@ void visit_load_constant(isel_context *ctx, nir_intrinsic_instr *instr)
void visit_discard_if(isel_context *ctx, nir_intrinsic_instr *instr)
{
if (ctx->cf_info.loop_nest_depth || ctx->cf_info.parent_if.is_divergent)
ctx->cf_info.exec_potentially_empty = true;
ctx->cf_info.exec_potentially_empty_discard = true;
ctx->program->needs_exact = true;
@ -3921,7 +3923,7 @@ void visit_discard(isel_context* ctx, nir_intrinsic_instr *instr)
Builder bld(ctx->program, ctx->block);
if (ctx->cf_info.loop_nest_depth || ctx->cf_info.parent_if.is_divergent)
ctx->cf_info.exec_potentially_empty = true;
ctx->cf_info.exec_potentially_empty_discard = true;
bool divergent = ctx->cf_info.parent_if.is_divergent ||
ctx->cf_info.parent_loop.has_divergent_continue;
@ -6768,7 +6770,7 @@ void visit_intrinsic(isel_context *ctx, nir_intrinsic_instr *instr)
bld.pseudo(aco_opcode::p_demote_to_helper, Operand(-1u));
if (ctx->cf_info.loop_nest_depth || ctx->cf_info.parent_if.is_divergent)
ctx->cf_info.exec_potentially_empty = true;
ctx->cf_info.exec_potentially_empty_discard = true;
ctx->block->kind |= block_kind_uses_demote;
ctx->program->needs_exact = true;
break;
@ -6779,7 +6781,7 @@ void visit_intrinsic(isel_context *ctx, nir_intrinsic_instr *instr)
bld.pseudo(aco_opcode::p_demote_to_helper, cond);
if (ctx->cf_info.loop_nest_depth || ctx->cf_info.parent_if.is_divergent)
ctx->cf_info.exec_potentially_empty = true;
ctx->cf_info.exec_potentially_empty_discard = true;
ctx->block->kind |= block_kind_uses_demote;
ctx->program->needs_exact = true;
break;
@ -7884,6 +7886,11 @@ void visit_jump(isel_context *ctx, nir_jump_instr *instr)
abort();
}
if (ctx->cf_info.parent_if.is_divergent && !ctx->cf_info.exec_potentially_empty_break) {
ctx->cf_info.exec_potentially_empty_break = true;
ctx->cf_info.exec_potentially_empty_break_depth = ctx->cf_info.loop_nest_depth;
}
/* remove critical edges from linear CFG */
bld.branch(aco_opcode::p_branch);
Block* break_block = ctx->program->create_and_insert_block();
@ -7948,6 +7955,7 @@ void visit_block(isel_context *ctx, nir_block *block)
static void visit_loop(isel_context *ctx, nir_loop *loop)
{
//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);
@ -7973,7 +7981,7 @@ static void visit_loop(isel_context *ctx, nir_loop *loop)
//TODO: what if a loop ends with a unconditional or uniformly branched continue and this branch is never taken?
if (!ctx->cf_info.has_branch) {
append_logical_end(ctx->block);
if (ctx->cf_info.exec_potentially_empty) {
if (ctx->cf_info.exec_potentially_empty_discard || ctx->cf_info.exec_potentially_empty_break) {
/* 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
@ -8081,10 +8089,16 @@ static void begin_divergent_if_then(isel_context *ctx, if_context *ic, Temp cond
ic->BB_endif.loop_nest_depth = ctx->cf_info.loop_nest_depth;
ic->BB_endif.kind |= (block_kind_merge | (ctx->block->kind & block_kind_top_level));
ic->exec_potentially_empty_old = ctx->cf_info.exec_potentially_empty;
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 = ctx->cf_info.exec_potentially_empty_break_depth;
ic->divergent_old = ctx->cf_info.parent_if.is_divergent;
ctx->cf_info.parent_if.is_divergent = true;
ctx->cf_info.exec_potentially_empty = false; /* divergent branches use cbranch_execz */
/* 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;
/** emit logical then block */
Block* BB_then_logical = ctx->program->create_and_insert_block();
@ -8129,8 +8143,14 @@ static void begin_divergent_if_else(isel_context *ctx, if_context *ic)
branch->operands[0] = Operand(ic->cond);
ctx->block->instructions.push_back(std::move(branch));
ic->exec_potentially_empty_old |= ctx->cf_info.exec_potentially_empty;
ctx->cf_info.exec_potentially_empty = false; /* divergent branches use cbranch_execz */
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);
/* 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;
/** emit logical else block */
Block* BB_else_logical = ctx->program->create_and_insert_block();
@ -8177,10 +8197,21 @@ static void end_divergent_if(isel_context *ctx, if_context *ic)
ctx->cf_info.parent_if.is_divergent = ic->divergent_old;
ctx->cf_info.exec_potentially_empty |= ic->exec_potentially_empty_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);
if (ctx->cf_info.loop_nest_depth == ctx->cf_info.exec_potentially_empty_break_depth &&
!ctx->cf_info.parent_if.is_divergent) {
ctx->cf_info.exec_potentially_empty_break = false;
ctx->cf_info.exec_potentially_empty_break_depth = UINT16_MAX;
}
/* uniform control flow never has an empty exec-mask */
if (!ctx->cf_info.loop_nest_depth && !ctx->cf_info.parent_if.is_divergent)
ctx->cf_info.exec_potentially_empty = false;
if (!ctx->cf_info.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;
}
}
static void visit_if(isel_context *ctx, nir_if *if_stmt)

7
src/amd/compiler/aco_instruction_selection_setup.cpp
View file

@ -68,7 +68,12 @@ struct isel_context {
struct {
bool is_divergent = false;
} parent_if;
bool exec_potentially_empty = 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
* and parent_if.is_divergent==false. Called _break but it's also used for
* loop continues. */
bool exec_potentially_empty_break = false;
std::unique_ptr<unsigned[]> nir_to_aco; /* NIR block index to ACO block index */
} cf_info;