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broadcom/compiler: improve generation of if conditions 

Where it is safe to do so, avoid the generation of code to convert a
condition code into a boolean which is then tested to generate a
condition code. This is only done in uniform ifs, and only for condition
values that are SSA and only used once (in that if statement).

shader-db relative to MR 7726:

total instructions in shared programs: 8985667 -> 8974151 (-0.13%)
instructions in affected programs: 390140 -> 378624 (-2.95%)
helped: 810
HURT: 276
helped stats (abs) min: 1 max: 49 x̄: 17.77 x̃: 16
helped stats (rel) min: 0.10% max: 33.63% x̄: 7.97% x̃: 6.45%
HURT stats (abs)   min: 1 max: 46 x̄: 10.42 x̃: 10
HURT stats (rel)   min: 0.16% max: 21.54% x̄: 2.26% x̃: 2.03%
95% mean confidence interval for instructions value: -11.46 -9.75
95% mean confidence interval for instructions %-change: -5.76% -4.97%
Instructions are helped.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8709>
This commit is contained in:
Arcady Goldmints-Orlov 2021-01-23 14:42:55 -05:00 committed by Marge Bot
parent b60dfa2c09
commit 93f8f83a95
1 changed files with 19 additions and 2 deletions
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21
src/broadcom/compiler/nir_to_vir.c
View File

@ -2788,6 +2788,20 @@ ntq_activate_execute_for_block(struct v3d_compile *c)
static void
ntq_emit_uniform_if(struct v3d_compile *c, nir_if *if_stmt)
{
/* If the if-statement's condition is only used once, emit it right before
* the if statement so as to use the resulting condition code directly.
* DCE will take care of the other comparison later.
*/
bool condition_emitted = false;
enum v3d_qpu_cond cond;
if (if_stmt->condition.is_ssa && list_length(&if_stmt->condition.use_link) == 1) {
nir_instr *comparison = if_stmt->condition.ssa->parent_instr;
if (comparison->type == nir_instr_type_alu) {
condition_emitted =
ntq_emit_comparison(c, nir_instr_as_alu(comparison), &cond);
}
}
nir_block *nir_else_block = nir_if_first_else_block(if_stmt);
bool empty_else_block =
(nir_else_block == nir_if_last_else_block(if_stmt) &&
@ -2801,8 +2815,11 @@ ntq_emit_uniform_if(struct v3d_compile *c, nir_if *if_stmt)
else
else_block = vir_new_block(c);
/* Set up the flags for the IF condition (taking the THEN branch). */
enum v3d_qpu_cond cond = ntq_emit_bool_to_cond(c, if_stmt->condition);
/* Set up the flags for the IF condition (taking the THEN branch),
* if we haven't already done so.
*/
if (!condition_emitted)
cond = ntq_emit_bool_to_cond(c, if_stmt->condition);
/* Jump to ELSE. */
struct qinst *branch = vir_BRANCH(c, cond == V3D_QPU_COND_IFA ?