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Code Issues 9 Packages Projects Releases Wiki Activity

ir3: optimize SSBO offset shifts for nir_opt_offsets 

The shifted offsets generated by ir3_nir_lower_io_offsets are not always
optimized well by nir_opt_offsets. If the offset to be shifted has the
form "iadd constant, foo" don't shift the result but transform it to
"iadd constant>>shift, (ushr foo, shift)". This ensures nir_opt_offsets
(which only looks for iadds) can fold the constant into the immediate
offset.

Signed-off-by: Job Noorman <jnoorman@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28664>
This commit is contained in:
Job Noorman 2024-04-10 10:43:38 +02:00 committed by Marge Bot
parent e37093b160
commit 57ea689273
1 changed files with 29 additions and 1 deletions
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30
src/freedreno/ir3/ir3_nir_lower_io_offsets.c
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@ -144,6 +144,34 @@ ir3_nir_try_propagate_bit_shift(nir_builder *b, nir_def *offset,
return new_offset;
}
static nir_def *
create_shift(nir_builder *b, nir_def *offset, int shift)
{
/* If the offset to be shifted has the form "iadd constant, foo" don't shift
* the result but transform it to "iadd constant>>shift, (ushr foo, shift)".
* This ensures nir_opt_offsets (which only looks for iadds) can fold the
* constant into the immediate offset.
*/
if (offset->parent_instr->type == nir_instr_type_alu) {
nir_alu_instr *offset_instr = nir_instr_as_alu(offset->parent_instr);
if (offset_instr->op == nir_op_iadd &&
nir_src_is_const(offset_instr->src[0].src)) {
nir_def *new_shift = ir3_nir_try_propagate_bit_shift(
b, offset_instr->src[1].src.ssa, -shift);
if (!new_shift)
new_shift = nir_ushr_imm(b, offset_instr->src[1].src.ssa, shift);
return nir_iadd_imm(
b, new_shift,
nir_src_as_const_value(offset_instr->src[0].src)->u32 >> shift);
}
}
return nir_ushr_imm(b, offset, shift);
}
static bool
lower_offset_for_ssbo(nir_intrinsic_instr *intrinsic, nir_builder *b,
unsigned ir3_ssbo_opcode, uint8_t offset_src_idx)
@ -208,7 +236,7 @@ lower_offset_for_ssbo(nir_intrinsic_instr *intrinsic, nir_builder *b,
if (new_offset)
offset = new_offset;
else
offset = nir_ushr_imm(b, offset, shift);
offset = create_shift(b, offset, shift);
/* Insert the new intrinsic right before the old one. */
nir_builder_instr_insert(b, &new_intrinsic->instr);