Module: Mesa
Branch: master
Commit: 7afa26d4e39c73502ad75b95605197eb52c8d099
URL:
http://cgit.freedesktop.org/mesa/mesa/commit/?id=7afa26d4e39c73502ad75b95605197eb52c8d099
Author: Eric Anholt <e...@anholt.net>
Date: Tue May 8 12:47:48 2018 -0700
nir: Add lowering for nir_op_bitfield_reverse.
This is basically the same as the GLSL lowering path.
Reviewed-by: Matt Turner <matts...@gmail.com>
Reviewed-by: Ian Romanick <ian.d.roman...@intel.com>
---
src/compiler/nir/nir.h | 2 ++
src/compiler/nir/nir_lower_alu.c | 47 +++++++++++++++++++++++++++++++++++++++-
2 files changed, 48 insertions(+), 1 deletion(-)
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 7d01eb23bc..06154aa990 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -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 */
diff --git a/src/compiler/nir/nir_lower_alu.c b/src/compiler/nir/nir_lower_alu.c
index 28ecaf6bad..ff977f0169 100644
--- a/src/compiler/nir/nir_lower_alu.c
+++ b/src/compiler/nir/nir_lower_alu.c
@@ -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) {
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