Mesa (master): glsl: Eliminate unused built-in variables after compilation
Ian Romanick
idr at kemper.freedesktop.org
Tue Sep 30 20:35:11 UTC 2014
Module: Mesa
Branch: master
Commit: 1012e95a40fe08f5d4f6219c1bc9812ad8f91423
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=1012e95a40fe08f5d4f6219c1bc9812ad8f91423
Author: Ian Romanick <ian.d.romanick at intel.com>
Date: Wed May 28 17:09:45 2014 -0700
glsl: Eliminate unused built-in variables after compilation
After compilation (and before linking) we can eliminate quite a few
built-in variables. Basically, any uniform or constant (e.g.,
gl_MaxVertexTextureImageUnits) that isn't used (with one exception) can
be eliminated. System values, vertex shader inputs (with one
exception), and fragment shader outputs that are not used and not
re-declared in the shader text can also be removed.
gl_ModelViewProjectMatrix and gl_Vertex are used by the built-in
function ftransform. There are some complications with eliminating
these variables (see the comment in the patch), so they are not
eliminated.
Valgrind massif results for a trimmed apitrace of dota2:
n time(i) total(B) useful-heap(B) extra-heap(B) stacks(B)
Before (32-bit): 46 40,661,487,174 75,116,800 68,854,065 6,262,735 0
After (32-bit): 50 40,564,927,443 69,185,408 63,683,871 5,501,537 0
Before (64-bit): 64 37,200,329,700 104,872,672 96,514,546 8,358,126 0
After (64-bit): 59 36,822,048,449 96,526,888 89,113,000 7,413,888 0
A real savings of 4.9MiB on 32-bit and 7.0MiB on 64-bit.
v2: Don't remove any built-in with Transpose in the name.
v3: Fix comment typo noticed by Anuj.
Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
Suggested-by: Eric Anholt <eric at anholt.net>
Reviewed-by: Matt Turner <mattst88 at gmail.com>
Acked-by: Anuj Phogat <anuj.phogat at gmail.com>
Cc: Eric Anholt <eric at anholt.net>
---
src/glsl/Makefile.sources | 1 +
src/glsl/glsl_parser_extras.cpp | 20 ++++++++
src/glsl/ir_optimization.h | 2 +
src/glsl/opt_dead_builtin_variables.cpp | 81 +++++++++++++++++++++++++++++++
4 files changed, 104 insertions(+)
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index cb8d5a6..bfb6993 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -87,6 +87,7 @@ LIBGLSL_FILES = \
$(GLSL_SRCDIR)/opt_copy_propagation.cpp \
$(GLSL_SRCDIR)/opt_copy_propagation_elements.cpp \
$(GLSL_SRCDIR)/opt_cse.cpp \
+ $(GLSL_SRCDIR)/opt_dead_builtin_variables.cpp \
$(GLSL_SRCDIR)/opt_dead_builtin_varyings.cpp \
$(GLSL_SRCDIR)/opt_dead_code.cpp \
$(GLSL_SRCDIR)/opt_dead_code_local.cpp \
diff --git a/src/glsl/glsl_parser_extras.cpp b/src/glsl/glsl_parser_extras.cpp
index 490c3c8..2da6d5a 100644
--- a/src/glsl/glsl_parser_extras.cpp
+++ b/src/glsl/glsl_parser_extras.cpp
@@ -1483,6 +1483,26 @@ _mesa_glsl_compile_shader(struct gl_context *ctx, struct gl_shader *shader,
;
validate_ir_tree(shader->ir);
+
+ enum ir_variable_mode other;
+ switch (shader->Stage) {
+ case MESA_SHADER_VERTEX:
+ other = ir_var_shader_in;
+ break;
+ case MESA_SHADER_FRAGMENT:
+ other = ir_var_shader_out;
+ break;
+ default:
+ /* Something invalid to ensure optimize_dead_builtin_uniforms
+ * doesn't remove anything other than uniforms or constants.
+ */
+ other = ir_var_mode_count;
+ break;
+ }
+
+ optimize_dead_builtin_variables(shader->ir, other);
+
+ validate_ir_tree(shader->ir);
}
if (shader->InfoLog)
diff --git a/src/glsl/ir_optimization.h b/src/glsl/ir_optimization.h
index 369dcd1..0c3a638 100644
--- a/src/glsl/ir_optimization.h
+++ b/src/glsl/ir_optimization.h
@@ -125,6 +125,8 @@ void lower_named_interface_blocks(void *mem_ctx, gl_shader *shader);
bool optimize_redundant_jumps(exec_list *instructions);
bool optimize_split_arrays(exec_list *instructions, bool linked);
bool lower_offset_arrays(exec_list *instructions);
+void optimize_dead_builtin_variables(exec_list *instructions,
+ enum ir_variable_mode other);
bool lower_vertex_id(gl_shader *shader);
diff --git a/src/glsl/opt_dead_builtin_variables.cpp b/src/glsl/opt_dead_builtin_variables.cpp
new file mode 100644
index 0000000..85c75d6
--- /dev/null
+++ b/src/glsl/opt_dead_builtin_variables.cpp
@@ -0,0 +1,81 @@
+/*
+ * Copyright © 2014 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include "ir.h"
+#include "ir_visitor.h"
+#include "ir_optimization.h"
+
+/**
+ * Pre-linking, optimize unused built-in variables
+ *
+ * Uniforms, constants, system values, inputs (vertex shader only), and
+ * outputs (fragment shader only) that are not used can be removed.
+ */
+void
+optimize_dead_builtin_variables(exec_list *instructions,
+ enum ir_variable_mode other)
+{
+ foreach_in_list_safe(ir_variable, var, instructions) {
+ if (var->ir_type != ir_type_variable || var->data.used)
+ continue;
+
+ if (var->data.mode != ir_var_uniform
+ && var->data.mode != ir_var_auto
+ && var->data.mode != ir_var_system_value
+ && var->data.mode != other)
+ continue;
+
+ /* So that linker rules can later be enforced, we cannot elimate
+ * variables that were redeclared in the shader code.
+ */
+ if ((var->data.mode == other || var->data.mode == ir_var_system_value)
+ && var->data.how_declared != ir_var_declared_implicitly)
+ continue;
+
+ if (strncmp(var->name, "gl_", 3) != 0)
+ continue;
+
+ /* gl_ModelViewProjectionMatrix and gl_Vertex are special because they
+ * are used by ftransform. No other built-in variable is used by a
+ * built-in function. The forward declarations of these variables in
+ * the built-in function shader does not have the "state slot"
+ * information, so removing these variables from the user shader will
+ * cause problems later.
+ *
+ * Matrix uniforms with "Transpose" are not eliminated because there's
+ * an optimization pass that can turn references to the regular matrix
+ * into references to the transpose matrix. Eliminating the transpose
+ * matrix would cause that pass to generate references to undeclareds
+ * variables (thank you, ir_validate).
+ *
+ * It doesn't seem worth the effort to track when the transpose could be
+ * eliminated (i.e., when the non-transpose was eliminated).
+ */
+ if (strcmp(var->name, "gl_ModelViewProjectionMatrix") == 0
+ || strcmp(var->name, "gl_Vertex") == 0
+ || strstr(var->name, "Transpose") != NULL)
+ continue;
+
+ var->remove();
+ }
+}
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