Re: [Mesa-dev] [PATCH 1/3] glsl: Use hash tables in opt_constant_variable().

[Tapani Pälli]

I did not get as impressive results with these 3 patches (how did you 
measure?) but on my machine (HSW GT2) complete shader_runner time goes 
from ~83 secs to ~70secs so it is definitely improving.

I simply do 'time bin/shader_runner' for the measurement.
Tested-by: Tapani Pälli <tapani.pa...@intel.com>

On 09/05/2015 12:21 PM, Kenneth Graunke wrote:
Cuts compile/link time of the fragment shader in bug #91857 by 31%
(31.79 -> 21.64).  It has over 8,000 variables so linked lists are
terrible.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91857
Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
---
  src/glsl/opt_constant_variable.cpp | 39 ++++++++++++++++++++------------------
  1 file changed, 21 insertions(+), 18 deletions(-)

diff --git a/src/glsl/opt_constant_variable.cpp 
b/src/glsl/opt_constant_variable.cpp
index 7aaaeed..cdfbc34 100644
--- a/src/glsl/opt_constant_variable.cpp
+++ b/src/glsl/opt_constant_variable.cpp
@@ -36,11 +36,11 @@
  #include "ir_visitor.h"
  #include "ir_optimization.h"
  #include "glsl_types.h"
+#include "util/hash_table.h"

  namespace {

  struct assignment_entry {
-   exec_node link;
     int assignment_count;
     ir_variable *var;
     ir_constant *constval;
@@ -54,31 +54,32 @@ public:
     virtual ir_visitor_status visit_enter(ir_assignment *);
     virtual ir_visitor_status visit_enter(ir_call *);

-   exec_list list;
+   struct hash_table *ht;
  };

  } /* unnamed namespace */

  static struct assignment_entry *
-get_assignment_entry(ir_variable *var, exec_list *list)
+get_assignment_entry(ir_variable *var, struct hash_table *ht)
  {
+   struct hash_entry *hte = _mesa_hash_table_search(ht, var);
     struct assignment_entry *entry;

-   foreach_list_typed(struct assignment_entry, entry, link, list) {
-      if (entry->var == var)
-        return entry;
+   if (hte) {
+      entry = (struct assignment_entry *) hte->data;
+   } else {
+      entry = (struct assignment_entry *) calloc(1, sizeof(*entry));
+      entry->var = var;
+      _mesa_hash_table_insert(ht, var, entry);
     }

-   entry = (struct assignment_entry *)calloc(1, sizeof(*entry));
-   entry->var = var;
-   list->push_head(&entry->link);
     return entry;
  }

  ir_visitor_status
  ir_constant_variable_visitor::visit(ir_variable *ir)
  {
-   struct assignment_entry *entry = get_assignment_entry(ir, &this->list);
+   struct assignment_entry *entry = get_assignment_entry(ir, this->ht);
     entry->our_scope = true;
     return visit_continue;
  }
@@ -97,7 +98,7 @@ ir_constant_variable_visitor::visit_enter(ir_assignment *ir)
     ir_constant *constval;
     struct assignment_entry *entry;

-   entry = get_assignment_entry(ir->lhs->variable_referenced(), &this->list);
+   entry = get_assignment_entry(ir->lhs->variable_referenced(), this->ht);
     assert(entry);
     entry->assignment_count++;

@@ -150,7 +151,7 @@ ir_constant_variable_visitor::visit_enter(ir_call *ir)
         struct assignment_entry *entry;

         assert(var);
-        entry = get_assignment_entry(var, &this->list);
+        entry = get_assignment_entry(var, this->ht);
         entry->assignment_count++;
        }
     }
@@ -161,7 +162,7 @@ ir_constant_variable_visitor::visit_enter(ir_call *ir)
        struct assignment_entry *entry;

        assert(var);
-      entry = get_assignment_entry(var, &this->list);
+      entry = get_assignment_entry(var, this->ht);
        entry->assignment_count++;
     }

@@ -177,20 +178,22 @@ do_constant_variable(exec_list *instructions)
     bool progress = false;
     ir_constant_variable_visitor v;

+   v.ht = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
+                                  _mesa_key_pointer_equal);
     v.run(instructions);

-   while (!v.list.is_empty()) {
-
-      struct assignment_entry *entry;
-      entry = exec_node_data(struct assignment_entry, v.list.head, link);
+   struct hash_entry *hte;
+   hash_table_foreach(v.ht, hte) {
+      struct assignment_entry *entry = (struct assignment_entry *) hte->data;

        if (entry->assignment_count == 1 && entry->constval && 
entry->our_scope) {
         entry->var->constant_value = entry->constval;
         progress = true;
        }
-      entry->link.remove();
+      hte->data = NULL;
        free(entry);
     }
+   _mesa_hash_table_destroy(v.ht, NULL);

     return progress;
  }

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