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nir: Add lowering for nir_op_bitfield_reverse. 

This is basically the same as the GLSL lowering path.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
This commit is contained in:
Eric Anholt 2018-05-08 12:47:48 -07:00
parent 6e1597c2d9
commit 7afa26d4e3
2 changed files with 48 additions and 1 deletions
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2
src/compiler/nir/nir.h
View File

@ -1911,6 +1911,8 @@ typedef struct nir_shader_compiler_options {
bool lower_bitfield_insert;
/** Lowers bitfield_insert to bfm, compares, and shifts. */
bool lower_bitfield_insert_to_shifts;
/** Lowers bitfield_reverse to shifts. */
bool lower_bitfield_reverse;
/** Lowers bfm to shifts and subtracts. */
bool lower_bfm;
/** Lowers ifind_msb to compare and ufind_msb */

47
src/compiler/nir/nir_lower_alu.c
View File

@ -50,6 +50,50 @@ lower_alu_instr(nir_alu_instr *instr, nir_builder *b)
b->exact = instr->exact;
switch (instr->op) {
case nir_op_bitfield_reverse:
if (b->shader->options->lower_bitfield_reverse) {
/* For more details, see:
*
* http://graphics.stanford.edu/~seander/bithacks.html#ReverseParallel
*/
nir_ssa_def *c1 = nir_imm_int(b, 1);
nir_ssa_def *c2 = nir_imm_int(b, 2);
nir_ssa_def *c4 = nir_imm_int(b, 4);
nir_ssa_def *c8 = nir_imm_int(b, 8);
nir_ssa_def *c16 = nir_imm_int(b, 16);
nir_ssa_def *c33333333 = nir_imm_int(b, 0x33333333);
nir_ssa_def *c55555555 = nir_imm_int(b, 0x55555555);
nir_ssa_def *c0f0f0f0f = nir_imm_int(b, 0x0f0f0f0f);
nir_ssa_def *c00ff00ff = nir_imm_int(b, 0x00ff00ff);
lowered = nir_ssa_for_alu_src(b, instr, 0);
/* Swap odd and even bits. */
lowered = nir_ior(b,
nir_iand(b, nir_ushr(b, lowered, c1), c55555555),
nir_ishl(b, nir_iand(b, lowered, c55555555), c1));
/* Swap consecutive pairs. */
lowered = nir_ior(b,
nir_iand(b, nir_ushr(b, lowered, c2), c33333333),
nir_ishl(b, nir_iand(b, lowered, c33333333), c2));
/* Swap nibbles. */
lowered = nir_ior(b,
nir_iand(b, nir_ushr(b, lowered, c4), c0f0f0f0f),
nir_ishl(b, nir_iand(b, lowered, c0f0f0f0f), c4));
/* Swap bytes. */
lowered = nir_ior(b,
nir_iand(b, nir_ushr(b, lowered, c8), c00ff00ff),
nir_ishl(b, nir_iand(b, lowered, c00ff00ff), c8));
lowered = nir_ior(b,
nir_ushr(b, lowered, c16),
nir_ishl(b, lowered, c16));
}
break;
case nir_op_imul_high:
case nir_op_umul_high:
if (b->shader->options->lower_mul_high) {
@ -136,7 +180,8 @@ nir_lower_alu(nir_shader *shader)
{
bool progress = false;
if (!shader->options->lower_mul_high)
if (!shader->options->lower_bitfield_reverse &&
!shader->options->lower_mul_high)
return false;
nir_foreach_function(function, shader) {