nir/constant_folding: Fold load_deref of nir_var_mem_constant
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6974>
diff --git a/src/compiler/nir/nir_opt_constant_folding.c b/src/compiler/nir/nir_opt_constant_folding.c
index a6e7066..6f8e3a8 100644
--- a/src/compiler/nir/nir_opt_constant_folding.c
+++ b/src/compiler/nir/nir_opt_constant_folding.c
@@ -28,6 +28,7 @@
#include "nir.h"
#include "nir_builder.h"
#include "nir_constant_expressions.h"
+#include "nir_deref.h"
#include <math.h>
/*
@@ -110,6 +111,74 @@
return true;
}
+static nir_const_value *
+const_value_for_deref(nir_deref_instr *deref)
+{
+ if (deref->mode != nir_var_mem_constant)
+ return NULL;
+
+ nir_deref_path path;
+ nir_deref_path_init(&path, deref, NULL);
+ if (path.path[0]->deref_type != nir_deref_type_var)
+ goto fail;
+
+ nir_variable *var = path.path[0]->var;
+ assert(var->data.mode == nir_var_mem_constant);
+ if (var->constant_initializer == NULL)
+ goto fail;
+
+ nir_constant *c = var->constant_initializer;
+ nir_const_value *v = NULL; /* Vector value for array-deref-of-vec */
+
+ for (unsigned i = 1; path.path[i] != NULL; i++) {
+ nir_deref_instr *p = path.path[i];
+ switch (p->deref_type) {
+ case nir_deref_type_var:
+ unreachable("Deref paths can only start with a var deref");
+
+ case nir_deref_type_array: {
+ assert(v == NULL);
+ if (!nir_src_is_const(p->arr.index))
+ goto fail;
+
+ uint64_t idx = nir_src_as_uint(p->arr.index);
+ if (c->num_elements > 0) {
+ assert(glsl_type_is_array(path.path[i-1]->type));
+ if (idx >= c->num_elements)
+ goto fail;
+ c = c->elements[idx];
+ } else {
+ assert(glsl_type_is_vector(path.path[i-1]->type));
+ assert(glsl_type_is_scalar(p->type));
+ if (idx >= NIR_MAX_VEC_COMPONENTS)
+ goto fail;
+ v = &c->values[idx];
+ }
+ break;
+ }
+
+ case nir_deref_type_struct:
+ assert(glsl_type_is_struct(path.path[i-1]->type));
+ assert(v == NULL && c->num_elements > 0);
+ if (p->strct.index >= c->num_elements)
+ goto fail;
+ c = c->elements[p->strct.index];
+ break;
+
+ default:
+ goto fail;
+ }
+ }
+
+ /* We have to have ended at a vector */
+ assert(c->num_elements == 0);
+ return v ? v : c->values;
+
+fail:
+ nir_deref_path_finish(&path);
+ return NULL;
+}
+
static bool
try_fold_intrinsic(nir_builder *b, nir_intrinsic_instr *instr,
struct constant_fold_state *state)
@@ -130,6 +199,17 @@
}
nir_instr_remove(&instr->instr);
progress = true;
+ } else if (instr->intrinsic == nir_intrinsic_load_deref) {
+ nir_deref_instr *deref = nir_src_as_deref(instr->src[0]);
+ nir_const_value *v = const_value_for_deref(deref);
+ if (v) {
+ b->cursor = nir_before_instr(&instr->instr);
+ nir_ssa_def *val = nir_build_imm(b, instr->dest.ssa.num_components,
+ instr->dest.ssa.bit_size, v);
+ nir_ssa_def_rewrite_uses(&instr->dest.ssa, nir_src_for_ssa(val));
+ nir_instr_remove(&instr->instr);
+ progress = true;
+ }
} else if (instr->intrinsic == nir_intrinsic_load_constant) {
state->has_load_constant = true;
