hir_field_selection.cpp

   1 /*
   2  * Copyright © 2010 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  21  * DEALINGS IN THE SOFTWARE.
  22  */
  23 #include <stdio.h>
  24 #include "main/imports.h"
  25 #include "symbol_table.h"
  26 #include "glsl_parser_extras.h"
  27 #include "ast.h"
  28 #include "glsl_types.h"
  29 #include "ir.h"
  30
  31 #define X 1
  32 #define R 5
  33 #define S 9
  34 #define I 13
  35
  36 static bool
  37 generate_swizzle(const char *str, ir_dereference *deref,
  38                  unsigned vector_length)
  39 {
  40    /* For each possible swizzle character, this table encodes the value in
  41     * \c idx_map that represents the 0th element of the vector.  For invalid
  42     * swizzle characters (e.g., 'k'), a special value is used that will allow
  43     * detection of errors.
  44     */
  45    static const unsigned char base_idx[26] = {
  46    /* a  b  c  d  e  f  g  h  i  j  k  l  m */
  47       R, R, I, I, I, I, R, I, I, I, I, I, I,
  48    /* n  o  p  q  r  s  t  u  v  w  x  y  z */
  49       I, I, S, S, R, S, S, I, I, X, X, X, X
  50    };
  51
  52    /* Each valid swizzle character has an entry in the previous table.  This
  53     * table encodes the base index encoded in the previous table plus the actual
  54     * index of the swizzle character.  When processing swizzles, the first
  55     * character in the string is indexed in the previous table.  Each character
  56     * in the string is indexed in this table, and the value found there has the
  57     * value form the first table subtracted.  The result must be on the range
  58     * [0,3].
  59     *
  60     * For example, the string "wzyx" will get X from the first table.  Each of
  61     * the charcaters will get X+3, X+2, X+1, and X+0 from this table.  After
  62     * subtraction, the swizzle values are { 3, 2, 1, 0 }.
  63     *
  64     * The string "wzrg" will get X from the first table.  Each of the characters
  65     * will get X+3, X+2, R+0, and R+1 from this table.  After subtraction, the
  66     * swizzle values are { 3, 2, 4, 5 }.  Since 4 and 5 are outside the range
  67     * [0,3], the error is detected.
  68     */
  69    static const unsigned char idx_map[26] = {
  70    /* a    b    c    d    e    f    g    h    i    j    k    l    m */
  71       R+3, R+2, 0,   0,   0,   0,   R+1, 0,   0,   0,   0,   0,   0,
  72    /* n    o    p    q    r    s    t    u    v    w    x    y    z */
  73       0,   0,   S+2, S+3, R+0, S+0, S+1, 0,   0,   X+3, X+0, X+1, X+2
  74    };
  75
  76    int swiz_idx[4] = { 0, 0, 0, 0 };
  77    unsigned i;
  78
  79
  80    /* Validate the first character in the swizzle string and look up the base
  81     * index value as described above.
  82     */
  83    if ((str[0] < 'a') || (str[0] > 'z'))
  84       return false;
  85
  86    const unsigned base = base_idx[str[0] - 'a'];
  87
  88
  89    for (i = 0; (i < 4) && (str[i] != '\0'); i++) {
  90       /* Validate the next character, and, as described above, convert it to a
  91        * swizzle index.
  92        */
  93       if ((str[i] < 'a') || (str[i] > 'z'))
  94          return false;
  95
  96       swiz_idx[i] = idx_map[str[i] - 'a'] - base;
  97       if ((swiz_idx[i] < 0) || (swiz_idx[i] >= (int) vector_length))
  98          return false;
  99    }
 100
 101    if (str[i] != '\0')
 102          return false;
 103
 104    deref->set_swizzle(swiz_idx[0], swiz_idx[1], swiz_idx[2], swiz_idx[3], i);
 105    return true;
 106 }
 107
 108
 109 struct ir_instruction *
 110 _mesa_ast_field_selection_to_hir(const ast_expression *expr,
 111                                  exec_list *instructions,
 112                                  struct _mesa_glsl_parse_state *state)
 113 {
 114    ir_instruction *op;
 115    ir_dereference *deref;
 116    YYLTYPE loc;
 117
 118
 119    op = expr->subexpressions[0]->hir(instructions, state);
 120    deref = new ir_dereference(op);
 121
 122    /* Initially assume that the resulting type of the field selection is an
 123     * error.  This make the error paths below a bit easier to follow.
 124     */
 125    deref->type = glsl_error_type;
 126
 127    /* If processing the thing being dereferenced generated an error, bail out
 128     * now.  Doing so prevents spurious error messages from being logged below.
 129     */
 130    if (is_error_type(op->type))
 131       return (struct ir_instruction *) deref;
 132
 133    /* There are two kinds of field selection.  There is the selection of a
 134     * specific field from a structure, and there is the selection of a
 135     * swizzle / mask from a vector.  Which is which is determined entirely
 136     * by the base type of the thing to which the field selection operator is
 137     * being applied.
 138     */
 139    loc = expr->get_location();
 140    if (op->type->is_vector()) {
 141       if (generate_swizzle(expr->primary_expression.identifier,
 142                            deref, op->type->vector_elements)) {
 143          /* Based on the number of elements in the swizzle and the base type
 144           * (i.e., float, int, unsigned, or bool) of the vector being swizzled,
 145           * generate the type of the resulting value.
 146           */
 147          deref->type =
 148             glsl_type::get_instance(op->type->base_type,
 149                                     deref->selector.swizzle.num_components,
 150                                     1);
 151       } else {
 152          /* FINISHME: Logging of error messages should be moved into
 153           * FINISHME: generate_swizzle.  This allows the generation of more
 154           * FINISHME: specific error messages.
 155           */
 156          _mesa_glsl_error(& loc, state, "Invalid swizzle / mask `%s'",
 157                           expr->primary_expression.identifier);
 158       }
 159    } else if (op->type->base_type == GLSL_TYPE_STRUCT) {
 160       /* FINISHME: Handle field selection from structures. */
 161    } else {
 162       _mesa_glsl_error(& loc, state, "Cannot access field `%s' of "
 163                        "non-structure / non-vector.",
 164                        expr->primary_expression.identifier);
 165    }
 166
 167    return (struct ir_instruction *) deref;
 168 }