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pan/bi: Implement csel fusing

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When generating csel instructions, we can peak to see what condition is
being used. If we're using a "nice" condition, we can fuse it in with
the csel itself, ideally letting the condition itself be DCE'd away.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4276>
This commit is contained in:
Alyssa Rosenzweig 2020-03-21 18:13:49 -04:00 • committed by Marge Bot
parent 5a02c871f2
commit 3f786ed10b
1 changed files with 65 additions and 21 deletions
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86
src/panfrost/bifrost/bifrost_compile.c
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@ -443,6 +443,64 @@ bi_cond_for_nir(nir_op op, bool soft)
}
}
static void
bi_copy_src(bi_instruction *alu, nir_alu_instr *instr, unsigned i, unsigned to,
unsigned *constants_left, unsigned *constant_shift)
{
unsigned bits = nir_src_bit_size(instr->src[i].src);
unsigned dest_bits = nir_dest_bit_size(instr->dest.dest);
alu->src_types[to] = nir_op_infos[instr->op].input_types[i]
| bits;
/* Try to inline a constant */
if (nir_src_is_const(instr->src[i].src) && *constants_left && (dest_bits == bits)) {
alu->constant.u64 |=
(nir_src_as_uint(instr->src[i].src)) << *constant_shift;
alu->src[to] = BIR_INDEX_CONSTANT | (*constant_shift);
--(*constants_left);
(*constant_shift) += dest_bits;
return;
}
alu->src[to] = bir_src_index(&instr->src[i].src);
/* We assert scalarization above */
alu->swizzle[to][0] = instr->src[i].swizzle[0];
}
static void
bi_fuse_csel_cond(bi_instruction *csel, nir_alu_src cond,
unsigned *constants_left, unsigned *constant_shift)
{
/* Bail for vector weirdness */
if (cond.swizzle[0] != 0)
return;
if (!cond.src.is_ssa)
return;
nir_ssa_def *def = cond.src.ssa;
nir_instr *parent = def->parent_instr;
if (parent->type != nir_instr_type_alu)
return;
nir_alu_instr *alu = nir_instr_as_alu(parent);
/* Try to match a condition */
enum bi_cond bcond = bi_cond_for_nir(alu->op, true);
if (bcond == BI_COND_ALWAYS)
return;
/* We found one, let's fuse it in */
csel->csel_cond = bcond;
bi_copy_src(csel, alu, 0, 0, constants_left, constant_shift);
bi_copy_src(csel, alu, 1, 3, constants_left, constant_shift);
}
static void
emit_alu(bi_context *ctx, nir_alu_instr *instr)
{
@ -485,27 +543,8 @@ emit_alu(bi_context *ctx, nir_alu_instr *instr)
unsigned num_inputs = nir_op_infos[instr->op].num_inputs;
assert(num_inputs <= ARRAY_SIZE(alu.src));
for (unsigned i = 0; i < num_inputs; ++i) {
unsigned bits = nir_src_bit_size(instr->src[i].src);
alu.src_types[i] = nir_op_infos[instr->op].input_types[i]
| bits;
/* Try to inline a constant */
if (nir_src_is_const(instr->src[i].src) && constants_left && (dest_bits == bits)) {
alu.constant.u64 |=
(nir_src_as_uint(instr->src[i].src)) << constant_shift;
alu.src[i] = BIR_INDEX_CONSTANT | constant_shift;
--constants_left;
constant_shift += dest_bits;
continue;
}
alu.src[i] = bir_src_index(&instr->src[i].src);
/* We assert scalarization above */
alu.swizzle[i][0] = instr->src[i].swizzle[0];
}
for (unsigned i = 0; i < num_inputs; ++i)
bi_copy_src(&alu, instr, i, i, &constants_left, &constant_shift);
/* Op-specific fixup */
switch (instr->op) {
@ -555,6 +594,11 @@ emit_alu(bi_context *ctx, nir_alu_instr *instr)
break;
}
if (alu.type == BI_CSEL) {
bi_fuse_csel_cond(&alu, instr->src[0],
&constants_left, &constant_shift);
}
bi_emit(ctx, alu);
}