Add shader and shader program caches.

2 files changed, 133 insertions, 3 deletions

diff --git a/gfx/src/render/render_backend.c b/gfx/src/render/render_backend.c
index fed906b..0fc8c85 100644
--- a/gfx/src/render/render_backend.c
+++ b/gfx/src/render/render_backend.c
@@ -3,12 +3,13 @@
 #include "gl_util.h"
 
 #include <GL/gl.h>
-#include <log/log.h>
+// #include <log/log.h>
 
 #include <assert.h>
 
 void gfx_init_render_backend(RenderBackend* render_backend) {
   assert(render_backend);
+
   mempool_make(&render_backend->buffers);
   mempool_make(&render_backend->framebuffers);
   mempool_make(&render_backend->geometries);
@@ -17,6 +18,9 @@ void gfx_init_render_backend(RenderBackend* render_backend) {
   mempool_make(&render_backend->shader_programs);
   mempool_make(&render_backend->textures);
 
+  mempool_make(&render_backend->shader_cache);
+  mempool_make(&render_backend->program_cache);
+
   glEnable(GL_CULL_FACE);
   glFrontFace(GL_CCW);
   glCullFace(GL_BACK);
@@ -259,10 +263,83 @@ void gfx_destroy_framebuffer(
 // Shaders.
 // -----------------------------------------------------------------------------
 
+static uint64_t hash_shader_desc(const ShaderDesc* desc) {
+  assert(desc);
+  // Note that defines may affect shader permutations, so we need to hash those
+  // as well.
+  uint64_t hash = 0;
+  for (size_t i = 0; i < desc->num_defines; ++i) {
+    const ShaderCompilerDefine* define = &desc->defines[i];
+    hash = (((hash << 13) + sstring_hash(define->name)) << 7) +
+           sstring_hash(define->value);
+  }
+  return (hash << 17) + cstring_hash(desc->code);
+}
+
+static uint64_t hash_program_desc(const ShaderProgramDesc* desc) {
+  assert(desc);
+  return ((uint64_t)desc->vertex_shader->id << 32) |
+         (uint64_t)desc->fragment_shader->id;
+}
+
+static Shader* find_cached_shader(ShaderCache* cache, uint64_t hash) {
+  assert(cache);
+  mempool_foreach(cache, entry, {
+    if (entry->hash == hash) {
+      return entry->shader;
+    }
+  });
+  return 0;
+}
+
+static ShaderProgram* find_cached_program(ProgramCache* cache, uint64_t hash) {
+  assert(cache);
+  mempool_foreach(cache, entry, {
+    if (entry->hash == hash) {
+      return entry->program;
+    }
+  });
+  return 0;
+}
+
+static ShaderCacheEntry* find_shader_cache_entry(
+    ShaderCache* cache, const Shader* shader) {
+  assert(cache);
+  assert(shader);
+  mempool_foreach(cache, entry, {
+    if (entry->shader == shader) {
+      return entry;
+    }
+  });
+  return 0;
+}
+
+static ShaderProgramCacheEntry* find_program_cache_entry(
+    ProgramCache* cache, const ShaderProgram* prog) {
+  assert(cache);
+  assert(prog);
+  mempool_foreach(cache, entry, {
+    if (entry->program == prog) {
+      return entry;
+    }
+  });
+  return 0;
+}
+
 Shader* gfx_make_shader(RenderBackend* render_backend, const ShaderDesc* desc) {
   assert(render_backend);
   assert(desc);
-  Shader* shader = mempool_alloc(&render_backend->shaders);
+
+  // Check the shader cache first.
+  ShaderCache*   cache  = &render_backend->shader_cache;
+  const uint64_t hash   = hash_shader_desc(desc);
+  Shader*        shader = find_cached_shader(cache, hash);
+  if (shader) {
+    // LOGD("Found cached shader with hash %lx", hash);
+    return shader;
+  }
+
+  shader = mempool_alloc(&render_backend->shaders);
   if (!shader) {
     return 0;
   }
@@ -270,6 +347,10 @@ Shader* gfx_make_shader(RenderBackend* render_backend, const ShaderDesc* desc) {
     mempool_free(&render_backend->shaders, &shader);
     return 0;
   }
+  ShaderCacheEntry* entry = mempool_alloc(cache);
+  assert(entry);
+  *entry = (ShaderCacheEntry){.hash = hash, .shader = shader};
+  // LOGD("Added shader with hash %lx to cache", hash);
   return shader;
 }
 
@@ -277,6 +358,13 @@ void gfx_destroy_shader(RenderBackend* render_backend, Shader** shader) {
   assert(render_backend);
   assert(shader);
   assert(*shader);
+
+  // Remove the shader from the cache.
+  ShaderCache*      cache = &render_backend->shader_cache;
+  ShaderCacheEntry* entry = find_shader_cache_entry(cache, *shader);
+  assert(entry); // Must be there, shaders can't go untracked.
+  mempool_free(cache, &entry);
+
   gfx_del_shader(*shader);
   mempool_free(&render_backend->shaders, shader);
 }
@@ -285,7 +373,17 @@ ShaderProgram* gfx_make_shader_program(
     RenderBackend* render_backend, const ShaderProgramDesc* desc) {
   assert(render_backend);
   assert(desc);
-  ShaderProgram* prog = mempool_alloc(&render_backend->shader_programs);
+
+  // Check the shader program cache first.
+  ProgramCache*  cache = &render_backend->program_cache;
+  const uint64_t hash  = hash_program_desc(desc);
+  ShaderProgram* prog  = find_cached_program(cache, hash);
+  if (prog) {
+    // LOGD("Found cached shader program with hash %lx", hash);
+    return prog;
+  }
+
+  prog = mempool_alloc(&render_backend->shader_programs);
   if (!prog) {
     return 0;
   }
@@ -293,6 +391,10 @@ ShaderProgram* gfx_make_shader_program(
     mempool_free(&render_backend->shader_programs, &prog);
     return 0;
   }
+  ShaderProgramCacheEntry* entry = mempool_alloc(cache);
+  assert(entry);
+  *entry = (ShaderProgramCacheEntry){.hash = hash, .program = prog};
+  // LOGD("Added shader program with hash %lx to cache", hash);
   return prog;
 }
 
@@ -301,6 +403,13 @@ void gfx_destroy_shader_program(
   assert(render_backend);
   assert(prog);
   assert(*prog);
+
+  // Remove the shader program from the cache.
+  ProgramCache*            cache = &render_backend->program_cache;
+  ShaderProgramCacheEntry* entry = find_program_cache_entry(cache, *prog);
+  assert(entry); // Must be there, shaders can't go untracked.
+  mempool_free(cache, &entry);
+
   gfx_del_shader_program(*prog);
   mempool_free(&render_backend->shader_programs, prog);
 }
diff --git a/gfx/src/render/render_backend_impl.h b/gfx/src/render/render_backend_impl.h
index 9e552c2..e149e98 100644
--- a/gfx/src/render/render_backend_impl.h
+++ b/gfx/src/render/render_backend_impl.h
@@ -13,6 +13,21 @@
 
 #include <mempool.h>
 
+#include <stdint.h>
+
+// TODO: Make a generic (hash, void*) structure and define functions over it.
+// Then define a macro that defines type-safe macros given the type of the
+// entry.
+typedef struct ShaderCacheEntry {
+  uint64_t hash;
+  Shader*  shader;
+} ShaderCacheEntry;
+
+typedef struct ShaderProgramCacheEntry {
+  uint64_t       hash;
+  ShaderProgram* program;
+} ShaderProgramCacheEntry;
+
 DEF_MEMPOOL(buffer_pool, Buffer, GFX_MAX_NUM_BUFFERS)
 DEF_MEMPOOL(framebuffer_pool, FrameBuffer, GFX_MAX_NUM_FRAMEBUFFERS)
 DEF_MEMPOOL(geometry_pool, Geometry, GFX_MAX_NUM_GEOMETRIES)
@@ -21,6 +36,9 @@ DEF_MEMPOOL(shader_pool, Shader, GFX_MAX_NUM_SHADERS)
 DEF_MEMPOOL(shader_program_pool, ShaderProgram, GFX_MAX_NUM_SHADER_PROGRAMS)
 DEF_MEMPOOL(texture_pool, Texture, GFX_MAX_NUM_TEXTURES)
 
+DEF_MEMPOOL(ShaderCache, ShaderCacheEntry, GFX_MAX_NUM_SHADERS)
+DEF_MEMPOOL(ProgramCache, ShaderProgramCacheEntry, GFX_MAX_NUM_SHADER_PROGRAMS)
+
 typedef struct {
   int width;
   int height;
@@ -36,6 +54,9 @@ typedef struct RenderBackend {
   shader_pool         shaders;
   shader_program_pool shader_programs;
   texture_pool        textures;
+  // Caches.
+  ShaderCache  shader_cache;
+  ProgramCache program_cache;
 } RenderBackend;
 
 /// Create a new render backend.