nir: clarify some nit_loop_info member names

Following commits will introduce additional fields such as
guessed_trip_count. Renaming these will help avoid confusion
as our unrolling feature set grows.

Reviewed-by: Thomas Helland <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>

3 files changed, 19 insertions, 17 deletions

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index cb8122def8a..fd1077fe37d 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -1886,9 +1886,11 @@ typedef struct {
    /* Number of instructions in the loop */
    unsigned num_instructions;
 
-   /* How many times the loop is run (if known) */
-   unsigned trip_count;
-   bool is_trip_count_known;
+   /* Maximum number of times the loop is run (if known) */
+   unsigned max_trip_count;
+
+   /* Do we know the exact number of times the loop will be run */
+   bool exact_trip_count_known;
 
    /* Unroll the loop regardless of its size */
    bool force_unroll;
diff --git a/src/compiler/nir/nir_loop_analyze.c b/src/compiler/nir/nir_loop_analyze.c
index c779383b365..700d1fe552b 100644
--- a/src/compiler/nir/nir_loop_analyze.c
+++ b/src/compiler/nir/nir_loop_analyze.c
@@ -527,7 +527,7 @@ find_trip_count(loop_info_state *state)
 {
    bool trip_count_known = true;
    nir_loop_terminator *limiting_terminator = NULL;
-   int min_trip_count = -1;
+   int max_trip_count = -1;
 
    list_for_each_entry(nir_loop_terminator, terminator,
                        &state->loop->info->loop_terminator_list,
@@ -606,8 +606,8 @@ find_trip_count(loop_info_state *state)
           * iterations than previously (we have identified a more limiting
           * terminator) set the trip count and limiting terminator.
           */
-         if (min_trip_count == -1 || iterations < min_trip_count) {
-            min_trip_count = iterations;
+         if (max_trip_count == -1 || iterations < max_trip_count) {
+            max_trip_count = iterations;
             limiting_terminator = terminator;
          }
          break;
@@ -617,9 +617,9 @@ find_trip_count(loop_info_state *state)
       }
    }
 
-   state->loop->info->is_trip_count_known = trip_count_known;
-   if (min_trip_count > -1)
-      state->loop->info->trip_count = min_trip_count;
+   state->loop->info->exact_trip_count_known = trip_count_known;
+   if (max_trip_count > -1)
+      state->loop->info->max_trip_count = max_trip_count;
    state->loop->info->limiting_terminator = limiting_terminator;
 }
 
@@ -639,7 +639,7 @@ force_unroll_array_access(loop_info_state *state, nir_deref_instr *deref)
       nir_deref_instr *parent = nir_deref_instr_parent(d);
       assert(glsl_type_is_array(parent->type) ||
              glsl_type_is_matrix(parent->type));
-      if (glsl_get_length(parent->type) == state->loop->info->trip_count)
+      if (glsl_get_length(parent->type) == state->loop->info->max_trip_count)
          return true;
 
       if (deref->mode & state->indirect_mask)
diff --git a/src/compiler/nir/nir_opt_loop_unroll.c b/src/compiler/nir/nir_opt_loop_unroll.c
index ea2012e292a..0e9966320b2 100644
--- a/src/compiler/nir/nir_opt_loop_unroll.c
+++ b/src/compiler/nir/nir_opt_loop_unroll.c
@@ -181,7 +181,7 @@ simple_unroll(nir_loop *loop)
    nir_cf_list unrolled_lp_body;
 
    /* Clone loop header and append to the loop body */
-   for (unsigned i = 0; i < loop->info->trip_count; i++) {
+   for (unsigned i = 0; i < loop->info->max_trip_count; i++) {
       /* Clone loop body */
       nir_cf_list_clone(&unrolled_lp_body, &loop_body, loop->cf_node.parent,
                         remap_table);
@@ -340,7 +340,7 @@ complex_unroll(nir_loop *loop, nir_loop_terminator *unlimit_term,
        * trip count == 1 we execute the code above the break twice and the
        * code below it once so we need clone things twice and so on.
        */
-      num_times_to_clone = loop->info->trip_count + 1;
+      num_times_to_clone = loop->info->max_trip_count + 1;
    } else {
       /* Pluck out the loop header */
       nir_cf_extract(&lp_header, nir_before_block(header_blk),
@@ -368,7 +368,7 @@ complex_unroll(nir_loop *loop, nir_loop_terminator *unlimit_term,
 
       nir_cf_node_remove(&limiting_term->nif->cf_node);
 
-      num_times_to_clone = loop->info->trip_count;
+      num_times_to_clone = loop->info->max_trip_count;
    }
 
    /* In the terminator that we have no trip count for move everything after
@@ -568,14 +568,14 @@ is_loop_small_enough_to_unroll(nir_shader *shader, nir_loop_info *li)
 {
    unsigned max_iter = shader->options->max_unroll_iterations;
 
-   if (li->trip_count > max_iter)
+   if (li->max_trip_count > max_iter)
       return false;
 
    if (li->force_unroll)
       return true;
 
    bool loop_not_too_large =
-      li->num_instructions * li->trip_count <= max_iter * LOOP_UNROLL_LIMIT;
+      li->num_instructions * li->max_trip_count <= max_iter * LOOP_UNROLL_LIMIT;
 
    return loop_not_too_large;
 }
@@ -641,7 +641,7 @@ process_loops(nir_shader *sh, nir_cf_node *cf_node, bool *has_nested_loop_out)
       if (!is_loop_small_enough_to_unroll(sh, loop->info))
          goto exit;
 
-      if (loop->info->is_trip_count_known) {
+      if (loop->info->exact_trip_count_known) {
          simple_unroll(loop);
          progress = true;
       } else {
@@ -665,7 +665,7 @@ process_loops(nir_shader *sh, nir_cf_node *cf_node, bool *has_nested_loop_out)
              * limiting terminator just do a simple unroll as the second
              * terminator can never be reached.
              */
-            if (loop->info->trip_count == 0 && !limiting_term_second) {
+            if (loop->info->max_trip_count == 0 && !limiting_term_second) {
                simple_unroll(loop);
             } else {
                complex_unroll(loop, terminator, limiting_term_second);