nir: Add infastructure for generating algebraic transformation passes

This commit builds on the nir_search.h infastructure by adding a bit of
python code that makes it stupid easy to write an algebraic transformation
pass.  The nir_algebraic.py file contains four python classes that
correspond directly to the datastructures in nir_search.c and allow you to
easily generate the C code to represent them.  Given a list of
search-and-replace operations, it can then generate a function that applies
those transformations to a shader.

The transformations can be specified manually, or they can be specified
using nested tuples.  The nested tuples make a neat little language for
specifying expression trees and search-and-replace operations in a very
readable and easy-to-edit fasion.

The generated code is also fairly efficient.  Insteady of blindly calling
nir_replace_instr with every single transformation and on every single
instruction, it uses a switch statement on the instruction opcode to do a
first-order culling and only calls nir_replace_instr if the opcode is known
to match the first opcode in the search expression.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>

diff --git a/src/glsl/nir/nir_algebraic.py b/src/glsl/nir/nir_algebraic.py
new file mode 100644 (file)
index 0000000..703102f
--- /dev/null
+++ b/src/glsl/nir/nir_algebraic.py
@@ -0,0 +1,255 @@
+#! /usr/bin/env python
+#
+# Copyright (C) 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.
+#
+# Authors:
+#    Jason Ekstrand (jason@jlekstrand.net)
+
+import itertools
+import struct
+import sys
+import mako.template
+
+# Represents a set of variables, each with a unique id
+class VarSet(object):
+   def __init__(self):
+      self.names = {}
+      self.ids = itertools.count()
+
+   def __getitem__(self, name):
+      if name not in self.names:
+         self.names[name] = self.ids.next()
+
+      return self.names[name]
+
+class Value(object):
+   @staticmethod
+   def create(val, name_base, varset):
+      if isinstance(val, tuple):
+         return Expression(val, name_base, varset)
+      elif isinstance(val, Expression):
+         return val
+      elif isinstance(val, (str, unicode)):
+         return Variable(val, name_base, varset)
+      elif isinstance(val, (bool, int, long, float)):
+         return Constant(val, name_base)
+
+   __template = mako.template.Template("""
+static const ${val.c_type} ${val.name} = {
+   { ${val.type_enum} },
+% if isinstance(val, Constant):
+   { ${hex(val)} /* ${val.value} */ },
+% elif isinstance(val, Variable):
+   ${val.index}, /* ${val.var_name} */
+% elif isinstance(val, Expression):
+   nir_op_${val.opcode},
+   { ${', '.join(src.c_ptr for src in val.sources)} },
+% endif
+};""")
+
+   def __init__(self, name, type_str):
+      self.name = name
+      self.type_str = type_str
+
+   @property
+   def type_enum(self):
+      return "nir_search_value_" + self.type_str
+
+   @property
+   def c_type(self):
+      return "nir_search_" + self.type_str
+
+   @property
+   def c_ptr(self):
+      return "&{0}.value".format(self.name)
+
+   def render(self):
+      return self.__template.render(val=self,
+                                    Constant=Constant,
+                                    Variable=Variable,
+                                    Expression=Expression)
+
+class Constant(Value):
+   def __init__(self, val, name):
+      Value.__init__(self, name, "constant")
+      self.value = val
+
+   def __hex__(self):
+      # Even if it's an integer, we still need to unpack as an unsigned
+      # int.  This is because, without C99, we can only assign to the first
+      # element of a union in an initializer.
+      if isinstance(self.value, (bool)):
+         return 'NIR_TRUE' if self.value else 'NIR_FALSE'
+      if isinstance(self.value, (int, long)):
+         return hex(struct.unpack('I', struct.pack('i', self.value))[0])
+      elif isinstance(self.value, float):
+         return hex(struct.unpack('I', struct.pack('f', self.value))[0])
+      else:
+         assert False
+
+class Variable(Value):
+   def __init__(self, val, name, varset):
+      Value.__init__(self, name, "variable")
+      self.var_name = val
+      self.index = varset[val]
+      self.name = name
+
+class Expression(Value):
+   def __init__(self, expr, name_base, varset):
+      Value.__init__(self, name_base, "expression")
+      assert isinstance(expr, tuple)
+
+      self.opcode = expr[0]
+      self.sources = [ Value.create(src, "{0}_{1}".format(name_base, i), varset)
+                       for (i, src) in enumerate(expr[1:]) ]
+
+   def render(self):
+      srcs = "\n".join(src.render() for src in self.sources)
+      return srcs + super(Expression, self).render()
+
+_optimization_ids = itertools.count()
+
+class SearchAndReplace(object):
+   def __init__(self, search, replace):
+      self.id = _optimization_ids.next()
+
+      varset = VarSet()
+      if isinstance(search, Expression):
+         self.search = search
+      else:
+         self.search = Expression(search, "search{0}".format(self.id), varset)
+
+      if isinstance(replace, Value):
+         self.replace = replace
+      else:
+         self.replace = Value.create(replace, "replace{0}".format(self.id), varset)
+
+_algebraic_pass_template = mako.template.Template("""
+#include "nir.h"
+#include "nir_search.h"
+
+struct transform {
+   const nir_search_expression *search;
+   const nir_search_value *replace;
+};
+
+% for (opcode, xform_list) in xform_dict.iteritems():
+% for xform in xform_list:
+   ${xform.search.render()}
+   ${xform.replace.render()}
+% endfor
+
+static const struct {
+   const nir_search_expression *search;
+   const nir_search_value *replace;
+} ${pass_name}_${opcode}_xforms[] = {
+% for xform in xform_list:
+   { &${xform.search.name}, ${xform.replace.c_ptr} },
+% endfor
+};
+% endfor
+
+struct opt_state {
+   void *mem_ctx;
+   bool progress;
+};
+
+static bool
+${pass_name}_block(nir_block *block, void *void_state)
+{
+   struct opt_state *state = void_state;
+
+   nir_foreach_instr_safe(block, instr) {
+      if (instr->type != nir_instr_type_alu)
+         continue;
+
+      nir_alu_instr *alu = nir_instr_as_alu(instr);
+      if (!alu->dest.dest.is_ssa)
+         continue;
+
+      switch (alu->op) {
+      % for opcode in xform_dict.keys():
+      case nir_op_${opcode}:
+         for (unsigned i = 0; i < ARRAY_SIZE(${pass_name}_${opcode}_xforms); i++) {
+            if (nir_replace_instr(alu, ${pass_name}_${opcode}_xforms[i].search,
+                                  ${pass_name}_${opcode}_xforms[i].replace,
+                                  state->mem_ctx))
+               state->progress = true;
+         }
+         break;
+      % endfor
+      default:
+         break;
+      }
+   }
+
+   return true;
+}
+
+static bool
+${pass_name}_impl(nir_function_impl *impl)
+{
+   struct opt_state state;
+
+   state.mem_ctx = ralloc_parent(impl);
+   state.progress = false;
+
+   nir_foreach_block(impl, ${pass_name}_block, &state);
+
+   if (state.progress)
+      nir_metadata_dirty(impl, nir_metadata_block_index |
+                               nir_metadata_dominance);
+
+   return state.progress;
+}
+
+bool
+${pass_name}(nir_shader *shader)
+{
+   bool progress = false;
+
+   nir_foreach_overload(shader, overload) {
+      if (overload->impl)
+         progress |= ${pass_name}_impl(overload->impl);
+   }
+
+   return progress;
+}
+""")
+
+class AlgebraicPass(object):
+   def __init__(self, pass_name, transforms):
+      self.xform_dict = {}
+      self.pass_name = pass_name
+
+      for xform in transforms:
+         if not isinstance(xform, SearchAndReplace):
+            xform = SearchAndReplace(*xform)
+
+         if xform.search.opcode not in self.xform_dict:
+            self.xform_dict[xform.search.opcode] = []
+
+         self.xform_dict[xform.search.opcode].append(xform)
+
+   def render(self):
+      return _algebraic_pass_template.render(pass_name=self.pass_name,
+                                             xform_dict=self.xform_dict)