1/*
2 * Copyright © 2018 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 DEALINGS
21 * IN THE SOFTWARE.
22 */
23
24#include "brw_nir.h"
25#include "compiler/nir/nir_builder.h"
26
27static nir_op
28get_conversion_op(nir_alu_type src_type,
29                  unsigned src_bit_size,
30                  nir_alu_type dst_type,
31                  unsigned dst_bit_size,
32                  nir_rounding_mode rounding_mode)
33{
34   nir_alu_type src_full_type = (nir_alu_type) (src_type | src_bit_size);
35   nir_alu_type dst_full_type = (nir_alu_type) (dst_type | dst_bit_size);
36
37   return nir_type_conversion_op(src_full_type, dst_full_type, rounding_mode);
38}
39
40static nir_rounding_mode
41get_opcode_rounding_mode(nir_op op)
42{
43   switch (op) {
44   case nir_op_f2f16_rtz:
45      return nir_rounding_mode_rtz;
46   case nir_op_f2f16_rtne:
47      return nir_rounding_mode_rtne;
48   default:
49      return nir_rounding_mode_undef;
50   }
51}
52
53static void
54split_conversion(nir_builder *b, nir_alu_instr *alu, nir_op op1, nir_op op2)
55{
56   b->cursor = nir_before_instr(&alu->instr);
57   assert(alu->dest.write_mask == 1);
58   nir_ssa_def *src = nir_ssa_for_alu_src(b, alu, 0);
59   nir_ssa_def *tmp = nir_build_alu(b, op1, src, NULL, NULL, NULL);
60   nir_ssa_def *res = nir_build_alu(b, op2, tmp, NULL, NULL, NULL);
61   nir_ssa_def_rewrite_uses(&alu->dest.dest.ssa, res);
62   nir_instr_remove(&alu->instr);
63}
64
65static bool
66lower_alu_instr(nir_builder *b, nir_alu_instr *alu)
67{
68   unsigned src_bit_size = nir_src_bit_size(alu->src[0].src);
69   nir_alu_type src_type = nir_op_infos[alu->op].input_types[0];
70   nir_alu_type src_full_type = (nir_alu_type) (src_type | src_bit_size);
71
72   unsigned dst_bit_size = nir_dest_bit_size(alu->dest.dest);
73   nir_alu_type dst_full_type = nir_op_infos[alu->op].output_type;
74   nir_alu_type dst_type = nir_alu_type_get_base_type(dst_full_type);
75
76   /* BDW PRM, vol02, Command Reference Instructions, mov - MOVE:
77    *
78    *   "There is no direct conversion from HF to DF or DF to HF.
79    *    Use two instructions and F (Float) as an intermediate type.
80    *
81    *    There is no direct conversion from HF to Q/UQ or Q/UQ to HF.
82    *    Use two instructions and F (Float) or a word integer type
83    *    or a DWord integer type as an intermediate type."
84    *
85    * It is important that the intermediate conversion happens through a
86    * 32-bit float type so we don't lose range when we convert from
87    * a 64-bit integer.
88    */
89   if ((src_full_type == nir_type_float16 && dst_bit_size == 64) ||
90       (src_bit_size == 64 && dst_full_type == nir_type_float16)) {
91      nir_op op1 = get_conversion_op(src_type, src_bit_size,
92                                     nir_type_float, 32,
93                                     nir_rounding_mode_undef);
94      nir_op op2 = get_conversion_op(nir_type_float, 32,
95                                     dst_type, dst_bit_size,
96                                     get_opcode_rounding_mode(alu->op));
97      split_conversion(b, alu, op1, op2);
98      return true;
99   }
100
101   /* SKL PRM, vol 02a, Command Reference: Instructions, Move:
102    *
103    *   "There is no direct conversion from B/UB to DF or DF to B/UB. Use
104    *    two instructions and a word or DWord intermediate type."
105    *
106    *   "There is no direct conversion from B/UB to Q/UQ or Q/UQ to B/UB.
107    *    Use two instructions and a word or DWord intermediate integer
108    *    type."
109    *
110    * It is important that we use a 32-bit integer matching the sign of the
111    * destination as the intermediate type so we avoid any chance of rtne
112    * rounding happening before the conversion to integer (which is expected
113    * to round towards zero) in double to byte conversions.
114    */
115   if ((src_bit_size == 8 && dst_bit_size == 64) ||
116       (src_bit_size == 64 && dst_bit_size == 8)) {
117      nir_op op1 = get_conversion_op(src_type, src_bit_size, dst_type, 32,
118                                     nir_rounding_mode_undef);
119      nir_op op2 = get_conversion_op(dst_type, 32, dst_type, dst_bit_size,
120                                     nir_rounding_mode_undef);
121      split_conversion(b, alu, op1, op2);
122      return true;
123   }
124
125   return false;
126}
127
128static bool
129lower_instr(nir_builder *b, nir_instr *instr, UNUSED void *cb_data)
130{
131   if (instr->type != nir_instr_type_alu)
132      return false;
133
134   nir_alu_instr *alu = nir_instr_as_alu(instr);
135   assert(alu->dest.dest.is_ssa);
136
137   if (!nir_op_infos[alu->op].is_conversion)
138      return false;
139
140   return lower_alu_instr(b, alu);
141}
142
143bool
144brw_nir_lower_conversions(nir_shader *shader)
145{
146   return nir_shader_instructions_pass(shader, lower_instr,
147                                       nir_metadata_block_index |
148                                       nir_metadata_dominance,
149                                       NULL);
150}
151