nir: add new constant folding infrastructure

Add a required field to the Opcode class, const_expr, that contains an
expression or statement that computes the result of the opcode given known
constant inputs. Then take those const_expr's and expand them into a function
that takes an opcode and an array of constant inputs and spits out the constant
result. This means that when adding opcodes, there's one less place to update,
and almost all the opcodes are self-documenting since the information on how to
compute the result is right next to the definition.

The helper functions in nir_constant_expressions.c were taken from
ir_constant_expressions.cpp.

v3 Jason Ekstrand <[email protected]>
 - Use mako to generate one function per opcode instead of doing piles of
   string splicing

v4 Jason Ekstrand <[email protected]>
 - More comments and better indentation in the mako
 - Add a description of the constant expression language in nir_opcodes.py
 - Added nir_constant_expressions.py to EXTRA_DIST in Makefile.am

Signed-off-by: Jason Ekstrand <[email protected]>
Reviewed-by: Connor Abbott <[email protected]>

1 files changed, 352 insertions, 0 deletions

diff --git a/src/glsl/nir/nir_constant_expressions.py b/src/glsl/nir/nir_constant_expressions.py
new file mode 100644
index 00000000000..22bc4f09583
--- /dev/null
+++ b/src/glsl/nir/nir_constant_expressions.py
@@ -0,0 +1,352 @@
+#! /usr/bin/python2
+template = """\
+/*
+ * 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 ([email protected])
+ */
+
+#include <math.h>
+#include "main/core.h"
+#include "nir_constant_expressions.h"
+
+#if defined(_MSC_VER) && (_MSC_VER < 1800)
+static int isnormal(double x)
+{
+   return _fpclass(x) == _FPCLASS_NN || _fpclass(x) == _FPCLASS_PN;
+}
+#elif defined(__SUNPRO_CC)
+#include <ieeefp.h>
+static int isnormal(double x)
+{
+   return fpclass(x) == FP_NORMAL;
+}
+#endif
+
+#if defined(_MSC_VER)
+static double copysign(double x, double y)
+{
+   return _copysign(x, y);
+}
+#endif
+
+/**
+ * Evaluate one component of packSnorm4x8.
+ */
+static uint8_t
+pack_snorm_1x8(float x)
+{
+    /* From section 8.4 of the GLSL 4.30 spec:
+     *
+     *    packSnorm4x8
+     *    ------------
+     *    The conversion for component c of v to fixed point is done as
+     *    follows:
+     *
+     *      packSnorm4x8: round(clamp(c, -1, +1) * 127.0)
+     *
+     * We must first cast the float to an int, because casting a negative
+     * float to a uint is undefined.
+     */
+   return (uint8_t) (int8_t)
+          _mesa_round_to_even(CLAMP(x, -1.0f, +1.0f) * 127.0f);
+}
+
+/**
+ * Evaluate one component of packSnorm2x16.
+ */
+static uint16_t
+pack_snorm_1x16(float x)
+{
+    /* From section 8.4 of the GLSL ES 3.00 spec:
+     *
+     *    packSnorm2x16
+     *    -------------
+     *    The conversion for component c of v to fixed point is done as
+     *    follows:
+     *
+     *      packSnorm2x16: round(clamp(c, -1, +1) * 32767.0)
+     *
+     * We must first cast the float to an int, because casting a negative
+     * float to a uint is undefined.
+     */
+   return (uint16_t) (int16_t)
+          _mesa_round_to_even(CLAMP(x, -1.0f, +1.0f) * 32767.0f);
+}
+
+/**
+ * Evaluate one component of unpackSnorm4x8.
+ */
+static float
+unpack_snorm_1x8(uint8_t u)
+{
+    /* From section 8.4 of the GLSL 4.30 spec:
+     *
+     *    unpackSnorm4x8
+     *    --------------
+     *    The conversion for unpacked fixed-point value f to floating point is
+     *    done as follows:
+     *
+     *       unpackSnorm4x8: clamp(f / 127.0, -1, +1)
+     */
+   return CLAMP((int8_t) u / 127.0f, -1.0f, +1.0f);
+}
+
+/**
+ * Evaluate one component of unpackSnorm2x16.
+ */
+static float
+unpack_snorm_1x16(uint16_t u)
+{
+    /* From section 8.4 of the GLSL ES 3.00 spec:
+     *
+     *    unpackSnorm2x16
+     *    ---------------
+     *    The conversion for unpacked fixed-point value f to floating point is
+     *    done as follows:
+     *
+     *       unpackSnorm2x16: clamp(f / 32767.0, -1, +1)
+     */
+   return CLAMP((int16_t) u / 32767.0f, -1.0f, +1.0f);
+}
+
+/**
+ * Evaluate one component packUnorm4x8.
+ */
+static uint8_t
+pack_unorm_1x8(float x)
+{
+    /* From section 8.4 of the GLSL 4.30 spec:
+     *
+     *    packUnorm4x8
+     *    ------------
+     *    The conversion for component c of v to fixed point is done as
+     *    follows:
+     *
+     *       packUnorm4x8: round(clamp(c, 0, +1) * 255.0)
+     */
+   return (uint8_t) _mesa_round_to_even(CLAMP(x, 0.0f, 1.0f) * 255.0f);
+}
+
+/**
+ * Evaluate one component packUnorm2x16.
+ */
+static uint16_t
+pack_unorm_1x16(float x)
+{
+    /* From section 8.4 of the GLSL ES 3.00 spec:
+     *
+     *    packUnorm2x16
+     *    -------------
+     *    The conversion for component c of v to fixed point is done as
+     *    follows:
+     *
+     *       packUnorm2x16: round(clamp(c, 0, +1) * 65535.0)
+     */
+   return (uint16_t) _mesa_round_to_even(CLAMP(x, 0.0f, 1.0f) * 65535.0f);
+}
+
+/**
+ * Evaluate one component of unpackUnorm4x8.
+ */
+static float
+unpack_unorm_1x8(uint8_t u)
+{
+    /* From section 8.4 of the GLSL 4.30 spec:
+     *
+     *    unpackUnorm4x8
+     *    --------------
+     *    The conversion for unpacked fixed-point value f to floating point is
+     *    done as follows:
+     *
+     *       unpackUnorm4x8: f / 255.0
+     */
+   return (float) u / 255.0f;
+}
+
+/**
+ * Evaluate one component of unpackUnorm2x16.
+ */
+static float
+unpack_unorm_1x16(uint16_t u)
+{
+    /* From section 8.4 of the GLSL ES 3.00 spec:
+     *
+     *    unpackUnorm2x16
+     *    ---------------
+     *    The conversion for unpacked fixed-point value f to floating point is
+     *    done as follows:
+     *
+     *       unpackUnorm2x16: f / 65535.0
+     */
+   return (float) u / 65535.0f;
+}
+
+/**
+ * Evaluate one component of packHalf2x16.
+ */
+static uint16_t
+pack_half_1x16(float x)
+{
+   return _mesa_float_to_half(x);
+}
+
+/**
+ * Evaluate one component of unpackHalf2x16.
+ */
+static float
+unpack_half_1x16(uint16_t u)
+{
+   return _mesa_half_to_float(u);
+}
+
+/* Some typed vector structures to make things like src0.y work */
+% for type in ["float", "int", "unsigned", "bool"]:
+struct ${type}_vec {
+   ${type} x;
+   ${type} y;
+   ${type} z;
+   ${type} w;
+};
+% endfor
+
+% for name, op in sorted(opcodes.iteritems()):
+static nir_const_value
+evaluate_${name}(unsigned num_components, nir_const_value *_src)
+{
+   nir_const_value _dst_val = { { {0, 0, 0, 0} } };
+
+   ## For each non-per-component input, create a variable srcN that
+   ## contains x, y, z, and w elements which are filled in with the
+   ## appropriately-typed values.
+   % for j in range(op.num_inputs):
+      % if op.input_sizes[j] == 0:
+         <% continue %>
+      % elif "src" + str(j) not in op.const_expr:
+         ## Avoid unused variable warnings
+         <% continue %>
+      %endif
+
+      struct ${op.input_types[j]}_vec src${j} = {
+      % for k in range(op.input_sizes[j]):
+         % if op.input_types[j] == "bool":
+            _src[${j}].u[${k}] != 0,
+         % else:
+            _src[${j}].${op.input_types[j][:1]}[${k}],
+         % endif
+      % endfor
+      };
+   % endfor
+
+   % if op.output_size == 0:
+      ## For per-component instructions, we need to iterate over the
+      ## components and apply the constant expression one component
+      ## at a time.
+      for (unsigned _i = 0; _i < num_components; _i++) {
+         ## For each per-component input, create a variable srcN that
+         ## contains the value of the current (_i'th) component.
+         % for j in range(op.num_inputs):
+            % if op.input_sizes[j] != 0:
+               <% continue %>
+            % elif "src" + str(j) not in op.const_expr:
+               ## Avoid unused variable warnings
+               <% continue %>
+            % elif op.input_types[j] == "bool":
+               bool src${j} = _src[${j}].u[_i] != 0;
+            % else:
+               ${op.input_types[j]} src${j} = _src[${j}].${op.input_types[j][:1]}[_i];
+            % endif
+         % endfor
+
+         ## Create an appropriately-typed variable dst and assign the
+         ## result of the const_expr to it.  If const_expr already contains
+         ## writes to dst, just include const_expr directly.
+         % if "dst" in op.const_expr:
+            ${op.output_type} dst;
+            ${op.const_expr}
+         % else:
+            ${op.output_type} dst = ${op.const_expr};
+         % endif
+
+         ## Store the current component of the actual destination to the
+         ## value of dst.
+         % if op.output_type == "bool":
+            ## Sanitize the C value to a proper NIR bool
+            _dst_val.u[_i] = dst ? NIR_TRUE : NIR_FALSE;
+         % else:
+            _dst_val.${op.output_type[:1]}[_i] = dst;
+         % endif
+      }
+   % else:
+      ## In the non-per-component case, create a struct dst with
+      ## appropriately-typed elements x, y, z, and w and assign the result
+      ## of the const_expr to all components of dst, or include the
+      ## const_expr directly if it writes to dst already.
+      struct ${op.output_type}_vec dst;
+
+      % if "dst" in op.const_expr:
+         ${op.const_expr}
+      % else:
+         ## Splat the value to all components.  This way expressions which
+         ## write the same value to all components don't need to explicitly
+         ## write to dest.  One such example is fnoise which has a
+         ## const_expr of 0.0f.
+         dst.x = dst.y = dst.z = dst.w = ${op.const_expr};
+      % endif
+
+      ## For each component in the destination, copy the value of dst to
+      ## the actual destination.
+      % for k in range(op.output_size):
+         % if op.output_type == "bool":
+            ## Sanitize the C value to a proper NIR bool
+            _dst_val.u[${k}] = dst.${"xyzw"[k]} ? NIR_TRUE : NIR_FALSE;
+         % else:
+            _dst_val.${op.output_type[:1]}[${k}] = dst.${"xyzw"[k]};
+         % endif
+      % endfor
+   % endif
+
+   return _dst_val;
+}
+% endfor
+
+nir_const_value
+nir_eval_const_opcode(nir_op op, unsigned num_components,
+                      nir_const_value *src)
+{
+   switch (op) {
+% for name in sorted(opcodes.iterkeys()):
+   case nir_op_${name}: {
+      return evaluate_${name}(num_components, src);
+      break;
+   }
+% endfor
+   default:
+      unreachable("shouldn't get here");
+   }
+}"""
+
+from nir_opcodes import opcodes
+from mako.template import Template
+
+print Template(template).render(opcodes=opcodes)