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nir/large_constants: Handle incomplete derefs

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This pass works entirely with variables, all we have to do is ignore any
derefs we see which we can't chase back to the variable.  The one
interesting case we have to handle is if we have a complex use of a
deref_var.  In that case, we have to flag it non-constant.

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6210>
This commit is contained in:
Jason Ekstrand 2020-07-15 20:12:33 -05:00 • committed by Marge Bot
parent 9f3c595dfc
commit df9596353a
1 changed files with 25 additions and 0 deletions
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25
src/compiler/nir/nir_opt_large_constants.c
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@ -199,6 +199,19 @@ nir_opt_large_constants(nir_shader *shader,
*/
nir_foreach_block(block, impl) {
nir_foreach_instr(instr, block) {
if (instr->type == nir_instr_type_deref) {
/* If we ever see a complex use of a deref_var, we have to assume
* that variable is non-constant because we can't guarantee we
* will find all of the writers of that variable.
*/
nir_deref_instr *deref = nir_instr_as_deref(instr);
if (deref->type == nir_deref_type_var &&
deref->mode == nir_var_function_temp &&
nir_deref_instr_has_complex_use(deref))
var_infos[deref->var->index].is_constant = false;
continue;
}
if (instr->type != nir_instr_type_intrinsic)
continue;
@ -228,6 +241,9 @@ nir_opt_large_constants(nir_shader *shader,
if (dst_deref && dst_deref->mode == nir_var_function_temp) {
nir_variable *var = nir_deref_instr_get_variable(dst_deref);
if (var == NULL)
continue;
assert(var->data.mode == nir_var_function_temp);
struct var_info *info = &var_infos[var->index];
@ -253,6 +269,9 @@ nir_opt_large_constants(nir_shader *shader,
if (src_deref && src_deref->mode == nir_var_function_temp) {
nir_variable *var = nir_deref_instr_get_variable(src_deref);
if (var == NULL)
continue;
assert(var->data.mode == nir_var_function_temp);
/* We only consider variables constant if all the reads are
@ -334,6 +353,9 @@ nir_opt_large_constants(nir_shader *shader,
continue;
nir_variable *var = nir_deref_instr_get_variable(deref);
if (var == NULL)
continue;
struct var_info *info = &var_infos[var->index];
if (info->is_constant) {
b.cursor = nir_after_instr(&intrin->instr);
@ -352,6 +374,9 @@ nir_opt_large_constants(nir_shader *shader,
continue;
nir_variable *var = nir_deref_instr_get_variable(deref);
if (var == NULL)
continue;
struct var_info *info = &var_infos[var->index];
if (info->is_constant) {
nir_instr_remove(&intrin->instr);