[Mesa-dev] [PATCH] nir: add lowering for idiv/udiv/umod
Rob Clark
robdclark at gmail.com
Fri Apr 3 08:21:57 PDT 2015
From: Rob Clark <robclark at freedesktop.org>
Based on the algo from NV50LegalizeSSA::handleDIV() and handleMOD().
See also trans_idiv() in freedreno/ir3/ir3_compiler.c (which was an
adaptation of the nv50 code from Ilia Mirkin).
Also, including a py script that implements the same algo with numpy,
based on something written by Ilia (and beaten on with a hammer a bit
by me).
I've tested this on i965 hacked up to insert the idiv lowering pass.
Signed-off-by: Rob Clark <robclark at freedesktop.org>
---
src/glsl/Makefile.sources | 1 +
src/glsl/nir/div-lowering.py | 75 ++++++++++++++++++++
src/glsl/nir/nir.h | 1 +
src/glsl/nir/nir_lower_idiv.c | 157 ++++++++++++++++++++++++++++++++++++++++++
4 files changed, 234 insertions(+)
create mode 100755 src/glsl/nir/div-lowering.py
create mode 100644 src/glsl/nir/nir_lower_idiv.c
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index ffce706..5d70e88 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -33,6 +33,7 @@ NIR_FILES = \
nir/nir_lower_atomics.c \
nir/nir_lower_global_vars_to_local.c \
nir/nir_lower_locals_to_regs.c \
+ nir/nir_lower_idiv.c \
nir/nir_lower_io.c \
nir/nir_lower_phis_to_scalar.c \
nir/nir_lower_samplers.cpp \
diff --git a/src/glsl/nir/div-lowering.py b/src/glsl/nir/div-lowering.py
new file mode 100755
index 0000000..87db784
--- /dev/null
+++ b/src/glsl/nir/div-lowering.py
@@ -0,0 +1,75 @@
+#!/usr/bin/python
+
+import numpy as np
+import sys
+
+op = sys.argv[1]
+
+if op not in ("idiv", "udiv", "umod"):
+ print "invalid op:", op
+ exit(1)
+
+is_signed = op == "idiv"
+
+if is_signed:
+ numer = np.int32(sys.argv[2])
+ denom = np.int32(sys.argv[3])
+else:
+ numer = np.uint32(sys.argv[2])
+ denom = np.uint32(sys.argv[3])
+
+print op, numer, denom, "\n"
+
+
+if is_signed:
+ af = np.float32(numer)
+ bf = np.float32(denom)
+ af = np.abs(af)
+ bf = np.abs(bf)
+ a = np.abs(numer).view(np.uint32)
+ b = np.abs(denom).view(np.uint32)
+else:
+ af = np.float32(numer)
+ bf = np.float32(denom)
+ a = numer
+ b = denom
+
+# get first result:
+bf = np.reciprocal(bf)
+bf = (bf.view(np.uint32) - np.uint32(2)).view(np.float32)
+q = af * bf
+
+if is_signed:
+ q = np.int32(q).view(np.uint32)
+else:
+ q = np.uint32(q).view(np.uint32)
+
+# get error of first result:
+r = q * b
+r = a - r
+r = np.float32(r)
+r = r * bf
+r = np.uint32(r)
+
+# add quotients:
+q = q + r
+
+# correction: if modulus >= divisor, add 1
+r = q * b
+r = a - r
+
+r = np.uint32(1) if r.view(np.uint32) >= b.view(np.uint32) else np.uint32(0)
+q = q + r
+
+if is_signed:
+ r = np.bitwise_xor(numer, denom)
+ r = np.right_shift(r, 31)
+ b = -q
+ q = b if r else q
+
+if op == "umod":
+ r = q * b
+ q = a - r
+
+print "=", q.view(np.int32)
+
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index c14c51c..20984e9 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1605,6 +1605,7 @@ void nir_lower_samplers(nir_shader *shader,
void nir_lower_system_values(nir_shader *shader);
void nir_lower_tex_projector(nir_shader *shader);
+void nir_lower_idiv(nir_shader *shader);
void nir_lower_atomics(nir_shader *shader);
void nir_lower_to_source_mods(nir_shader *shader);
diff --git a/src/glsl/nir/nir_lower_idiv.c b/src/glsl/nir/nir_lower_idiv.c
new file mode 100644
index 0000000..c2f08df
--- /dev/null
+++ b/src/glsl/nir/nir_lower_idiv.c
@@ -0,0 +1,157 @@
+/*
+ * Copyright © 2015 Red Hat
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Authors:
+ * Rob Clark <robclark at freedesktop.org>
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+/* Lowers idiv/udiv/umod
+ * Based on NV50LegalizeSSA::handleDIV()
+ *
+ * Note that this is probably not enough precision for compute shaders.
+ * Perhaps we want a second higher precision (looping) version of this?
+ * Or perhaps we assume if you can do compute shaders you can also
+ * branch out to a pre-optimized shader library routine..
+ */
+
+static void
+convert_instr(nir_builder *bld, nir_alu_instr *alu)
+{
+ nir_ssa_def *numer, *denom, *af, *bf, *a, *b, *q, *r;
+ nir_op op = alu->op;
+ bool is_signed;
+
+ if ((op != nir_op_idiv) &&
+ (op != nir_op_udiv) &&
+ (op != nir_op_umod))
+ return;
+
+ is_signed = (op == nir_op_idiv);
+
+ nir_builder_insert_before_instr(bld, &alu->instr);
+
+ numer = nir_ssa_for_src(bld, alu->src[0].src,
+ nir_ssa_alu_instr_src_components(alu, 0));
+ denom = nir_ssa_for_src(bld, alu->src[1].src,
+ nir_ssa_alu_instr_src_components(alu, 1));
+
+ if (is_signed) {
+ af = nir_i2f(bld, numer);
+ bf = nir_i2f(bld, denom);
+ af = nir_fabs(bld, af);
+ bf = nir_fabs(bld, bf);
+ a = nir_iabs(bld, numer);
+ b = nir_iabs(bld, denom);
+ } else {
+ af = nir_u2f(bld, numer);
+ bf = nir_u2f(bld, denom);
+ a = numer;
+ b = denom;
+ }
+
+ /* get first result: */
+ bf = nir_frcp(bld, bf);
+ bf = nir_isub(bld, bf, nir_imm_int(bld, 2)); /* yes, really */
+ q = nir_fmul(bld, af, bf);
+
+ if (is_signed) {
+ q = nir_f2i(bld, q);
+ } else {
+ q = nir_f2u(bld, q);
+ }
+
+ /* get error of first result: */
+ r = nir_imul(bld, q, b);
+ r = nir_isub(bld, a, r);
+ r = nir_u2f(bld, r);
+ r = nir_fmul(bld, r, bf);
+ r = nir_f2u(bld, r);
+
+ /* add quotients: */
+ q = nir_iadd(bld, q, r);
+
+ /* correction: if modulus >= divisor, add 1 */
+ r = nir_imul(bld, q, b);
+ r = nir_isub(bld, a, r);
+
+ r = nir_ige(bld, r, b);
+ r = nir_b2i(bld, r);
+
+ q = nir_iadd(bld, q, r);
+ if (is_signed) {
+ /* fix the sign: */
+ r = nir_ixor(bld, numer, denom);
+ r = nir_ushr(bld, r, nir_imm_int(bld, 31));
+ r = nir_i2b(bld, r);
+ b = nir_ineg(bld, q);
+ q = nir_bcsel(bld, r, b, q);
+ }
+
+ if (op == nir_op_umod) {
+ /* division result in q */
+ r = nir_imul(bld, q, b);
+ q = nir_isub(bld, a, r);
+ }
+
+ assert(alu->dest.dest.is_ssa);
+ nir_ssa_def_rewrite_uses(&alu->dest.dest.ssa,
+ nir_src_for_ssa(q),
+ ralloc_parent(alu));
+}
+
+static bool
+convert_block(nir_block *block, void *state)
+{
+ nir_builder *b = state;
+
+ nir_foreach_instr_safe(block, instr) {
+ if (instr->type == nir_instr_type_alu)
+ convert_instr(b, nir_instr_as_alu(instr));
+ }
+
+ return true;
+}
+
+static void
+convert_impl(nir_function_impl *impl)
+{
+ nir_builder b;
+ nir_builder_init(&b, impl);
+
+ nir_foreach_block(impl, convert_block, &b);
+ nir_metadata_preserve(impl, nir_metadata_block_index |
+ nir_metadata_dominance);
+}
+
+void
+nir_lower_idiv(nir_shader *shader)
+{
+ nir_foreach_overload(shader, overload) {
+ if (overload->impl)
+ convert_impl(overload->impl);
+ }
+
+ exec_list_make_empty(&shader->system_values);
+}
--
2.1.0
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