[Mesa-dev] [PATCH] glsl: Eliminate unused built-in variables after compilation
Ian Romanick
idr at freedesktop.org
Thu May 29 14:37:34 PDT 2014
From: Ian Romanick <ian.d.romanick at intel.com>
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.
Reduces the peak ir_variable memory usage in a trimmed apitrace of dota2
by 3.5MB on 64-bit.
Before: IR MEM: variable usage / name / total: 5327760 894914 6222674
After: IR MEM: variable usage / name / total: 2156568 318192 2474760
Reduces the peak ir_variable memory usage in a trimmed apitrace of dota2
by 2.8MB on 32-bit.
Before: IR MEM: variable usage / name / total: 4118280 644100 4762380
After: IR MEM: variable usage / name / total: 1473408 256871 1730279
v2: Don't remove any built-in with Transpose in the name.
Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
Suggested-by: Eric Anholt <eric at anholt.net>
Cc: Eric Anholt <eric at anholt.net>
Cc: Tapani Pälli <tapani.palli at intel.com>
Cc: Eero Tamminen <eero.t.tamminen at intel.com>
---
After my last edit, I re-ran piglit, re-ran the apitrace, and did 'git
commit --amend' instead of 'git commit --amend -a'. :(
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 | 83 +++++++++++++++++++++++++++++++++
4 files changed, 106 insertions(+)
create mode 100644 src/glsl/opt_dead_builtin_variables.cpp
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index 6e230f7..a733323 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -88,6 +88,7 @@ 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 d3339e7..323cb23 100644
--- a/src/glsl/glsl_parser_extras.cpp
+++ b/src/glsl/glsl_parser_extras.cpp
@@ -1485,6 +1485,26 @@ _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 invalide 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 c63921c..2dfd81e 100644
--- a/src/glsl/ir_optimization.h
+++ b/src/glsl/ir_optimization.h
@@ -122,6 +122,8 @@ 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);
ir_rvalue *
compare_index_block(exec_list *instructions, ir_variable *index,
diff --git a/src/glsl/opt_dead_builtin_variables.cpp b/src/glsl/opt_dead_builtin_variables.cpp
new file mode 100644
index 0000000..afe22f2
--- /dev/null
+++ b/src/glsl/opt_dead_builtin_variables.cpp
@@ -0,0 +1,83 @@
+/*
+ * 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_list_safe(n, instructions) {
+ ir_variable *const var = ((ir_instruction *) n)->as_variable();
+
+ if (var == NULL || 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();
+ }
+}
--
1.8.1.4
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