1 /*
2 * Copyright 2024 Alyssa Rosenzweig
3 * SPDX-License-Identifier: MIT
4 */
5
6 #include "util/bitset.h"
7 #include "util/half_float.h"
8 #include "agx_builder.h"
9 #include "agx_compiler.h"
10 #include "agx_opcodes.h"
11
12 /*
13 * AGX can convert 16-bit sources to 32-bit for free, so it's beneficial to
14 * compact 32-bit constants down to 16-bit when doing so is lossless. This
15 * reduces register pressure (GPR or uniform, depending on whether the constant
16 * is promoted).
17 */
18 void
agx_opt_compact_constants(agx_context * ctx)19 agx_opt_compact_constants(agx_context *ctx)
20 {
21 /* TODO: Handle ints too */
22 BITSET_WORD *src_float = calloc(ctx->alloc, sizeof(BITSET_WORD));
23 BITSET_WORD *src_other = calloc(ctx->alloc, sizeof(BITSET_WORD));
24 BITSET_WORD *replaced = calloc(ctx->alloc, sizeof(BITSET_WORD));
25
26 /* Analyze the types that we read constants as */
27 agx_foreach_instr_global(ctx, I) {
28 agx_foreach_ssa_src(I, s) {
29 if (agx_is_float_src(I, s))
30 BITSET_SET(src_float, I->src[s].value);
31 else
32 BITSET_SET(src_other, I->src[s].value);
33 }
34 }
35
36 agx_foreach_instr_global(ctx, I) {
37 if (I->op == AGX_OPCODE_MOV_IMM && I->dest[0].size == AGX_SIZE_32) {
38 unsigned v = I->dest[0].value;
39
40 if (BITSET_TEST(src_float, v) && !BITSET_TEST(src_other, v)) {
41 /* Try to compact to f16 */
42 uint16_t compact = _mesa_float_to_half(uif(I->imm));
43
44 if (I->imm == fui(_mesa_half_to_float(compact))) {
45 I->dest[0].size = AGX_SIZE_16;
46 I->imm = compact;
47 BITSET_SET(replaced, v);
48 }
49 }
50 } else {
51 agx_foreach_ssa_src(I, s) {
52 if (BITSET_TEST(replaced, I->src[s].value)) {
53 I->src[s].size = AGX_SIZE_16;
54 }
55 }
56 }
57 }
58
59 free(replaced);
60 free(src_float);
61 free(src_other);
62 }
63