1/*
2 * Copyright (C) 2021 Alyssa Rosenzweig <alyssa@rosenzweig.io>
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 FROM,
20 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 * SOFTWARE.
22 */
23
24#include "agx_compiler.h"
25
26/* SSA-based scalar dead code elimination */
27
28void
29agx_dce(agx_context *ctx)
30{
31   BITSET_WORD *seen = calloc(BITSET_WORDS(ctx->alloc), sizeof(BITSET_WORD));
32
33   agx_foreach_instr_global_safe_rev(ctx, I) {
34      if (agx_opcodes_info[I->op].can_eliminate) {
35         bool needed = false;
36
37         agx_foreach_dest(I, d) {
38            if (I->dest[d].type == AGX_INDEX_NORMAL)
39               needed |= BITSET_TEST(seen, I->dest[d].value);
40            else if (I->dest[d].type != AGX_INDEX_NULL)
41               needed = true;
42         }
43
44         if (!needed) {
45            agx_remove_instruction(I);
46            continue;
47         }
48      }
49
50      agx_foreach_src(I, s) {
51         if (I->src[s].type == AGX_INDEX_NORMAL)
52            BITSET_SET(seen, I->src[s].value);
53      }
54   }
55
56   free(seen);
57}
58