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aco: refactor get_reg_simple() to return early on exact matches 

in the best fit algorithm

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4573>
This commit is contained in:
Daniel Schürmann 2020-04-14 11:43:39 +01:00 committed by Marge Bot
parent 6792e134f3
commit 2796cb4c24
1 changed files with 23 additions and 26 deletions
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49
src/amd/compiler/aco_register_allocation.cpp
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@ -393,7 +393,6 @@ std::pair<PhysReg, bool> get_reg_simple(ra_ctx& ctx,
stride = 1; /* stride in full registers */
}
/* best fit algorithm: find the smallest gap to fit in the variable */
if (stride == 1) {
if (rc.type() == RegType::vgpr && (size == 4 || size == 8)) {
@ -403,41 +402,39 @@ std::pair<PhysReg, bool> get_reg_simple(ra_ctx& ctx,
return res;
}
/* best fit algorithm: find the smallest gap to fit in the variable */
unsigned best_pos = 0xFFFF;
unsigned gap_size = 0xFFFF;
unsigned next_pos = 0xFFFF;
unsigned last_pos = 0xFFFF;
for (unsigned current_reg = lb; current_reg < ub; current_reg++) {
if (reg_file[current_reg] != 0 || ctx.war_hint[current_reg]) {
if (next_pos == 0xFFFF)
continue;
/* check if the variable fits */
if (next_pos + size > current_reg) {
next_pos = 0xFFFF;
continue;
}
/* check if the tested gap is smaller */
if (current_reg - next_pos < gap_size) {
best_pos = next_pos;
gap_size = current_reg - next_pos;
}
next_pos = 0xFFFF;
if (reg_file[current_reg] == 0 && !ctx.war_hint[current_reg]) {
if (last_pos == 0xFFFF)
last_pos = current_reg;
continue;
}
if (next_pos == 0xFFFF)
next_pos = current_reg;
if (last_pos == 0xFFFF)
continue;
/* early return on exact matches */
if (last_pos + size == current_reg) {
adjust_max_used_regs(ctx, rc, last_pos);
return {PhysReg{last_pos}, true};
}
/* check if it fits and the gap size is smaller */
if (last_pos + size < current_reg && current_reg - last_pos < gap_size) {
best_pos = last_pos;
gap_size = current_reg - last_pos;
}
last_pos = 0xFFFF;
}
/* final check */
if (next_pos != 0xFFFF &&
next_pos + size <= ub &&
ub - next_pos < gap_size) {
best_pos = next_pos;
gap_size = ub - next_pos;
}
if (last_pos + size <= ub && ub - last_pos < gap_size)
best_pos = last_pos;
if (best_pos != 0xFFFF) {
adjust_max_used_regs(ctx, rc, best_pos);
return {PhysReg{best_pos}, true};