#include "nir.h"
#include "nir_builder.h"
+#include "util/mesa-sha1.h"
+#include <math.h>
/** @file nir_opt_undef.c
*
* Handles optimization of operations involving ssa_undef.
*/
+struct undef_options {
+ bool disallow_undef_to_nan;
+};
+
/**
* Turn conditional selects between an undef and some other value into a move
* of that other value (on the assumption that the condition's going to be
return true;
}
+struct visit_info {
+ bool replace_undef_with_constant;
+ bool prefer_nan;
+ bool must_keep_undef;
+};
+
+/**
+ * Analyze an undef use to see if replacing undef with a constant is
+ * beneficial.
+ */
+static void
+visit_undef_use(nir_src *src, struct visit_info *info)
+{
+ nir_instr *instr = src->parent_instr;
+
+ if (src->is_if) {
+ /* If the use is "if", keep undef because the branch will be eliminated
+ * by nir_opt_dead_cf.
+ */
+ info->must_keep_undef = true;
+ return;
+ }
+
+ if (instr->type == nir_instr_type_alu) {
+ /* Replacing undef with a constant is only beneficial with ALU
+ * instructions because it can eliminate them or simplify them.
+ */
+ nir_alu_instr *alu = nir_instr_as_alu(instr);
+
+ /* Follow movs and vecs.
+ *
+ * Note that all vector component uses are followed and swizzles are
+ * ignored.
+ */
+ if (alu->op == nir_op_mov || nir_op_is_vec(alu->op)) {
+ nir_foreach_use_including_if(next_src, &alu->def) {
+ visit_undef_use(next_src, info);
+ }
+ return;
+ }
+
+ unsigned num_srcs = nir_op_infos[alu->op].num_inputs;
+
+ for (unsigned i = 0; i < num_srcs; i++) {
+ if (&alu->src[i].src != src)
+ continue;
+
+ if (nir_op_is_selection(alu->op) && i != 0) {
+ /* nir_opt_algebraic can eliminate a select opcode only if src0 is
+ * a constant. If the undef use is src1 or src2, it will be
+ * handled by opt_undef_csel.
+ */
+ continue;
+ }
+
+ info->replace_undef_with_constant = true;
+ if (nir_op_infos[alu->op].input_types[i] & nir_type_float &&
+ alu->op != nir_op_fmulz &&
+ (alu->op != nir_op_ffmaz || i == 2))
+ info->prefer_nan = true;
+ }
+ } else {
+ /* If the use is not ALU, don't replace undef. We need to preserve
+ * undef for stores and phis because those are handled differently,
+ * and replacing undef with a constant would result in worse code.
+ */
+ info->must_keep_undef = true;
+ return;
+ }
+}
+
+/**
+ * Replace ssa_undef used by ALU opcodes with 0 or NaN, whichever eliminates
+ * more code.
+ *
+ * Replace it with NaN if an FP opcode uses undef, which will cause the opcode
+ * to be eliminated by nir_opt_algebraic. 0 would not eliminate the FP opcode.
+ */
+static bool
+replace_ssa_undef(nir_builder *b, nir_instr *instr,
+ const struct undef_options *options)
+{
+ nir_undef_instr *undef = nir_instr_as_undef(instr);
+ struct visit_info info = {0};
+
+ nir_foreach_use_including_if(src, &undef->def) {
+ visit_undef_use(src, &info);
+ }
+
+ if (info.must_keep_undef || !info.replace_undef_with_constant)
+ return false;
+
+ b->cursor = nir_before_instr(&undef->instr);
+ nir_def *replacement;
+
+ /* If undef is used as float, replace it with NaN, which will
+ * eliminate all FP instructions that consume it. Else, replace it
+ * with 0, which is more likely to eliminate non-FP instructions.
+ */
+ if (info.prefer_nan && !options->disallow_undef_to_nan)
+ replacement = nir_imm_floatN_t(b, NAN, undef->def.bit_size);
+ else
+ replacement = nir_imm_intN_t(b, 0, undef->def.bit_size);
+
+ if (undef->def.num_components > 1)
+ replacement = nir_replicate(b, replacement, undef->def.num_components);
+
+ nir_def_rewrite_uses_after(&undef->def, replacement, &undef->instr);
+ nir_instr_remove(&undef->instr);
+ return true;
+}
+
static bool
nir_opt_undef_instr(nir_builder *b, nir_instr *instr, void *data)
{
- if (instr->type == nir_instr_type_alu) {
+ const struct undef_options *options = data;
+
+ if (instr->type == nir_instr_type_undef) {
+ return replace_ssa_undef(b, instr, options);
+ } else if (instr->type == nir_instr_type_alu) {
nir_alu_instr *alu = nir_instr_as_alu(instr);
return opt_undef_csel(b, alu) ||
opt_undef_vecN(b, alu) ||
bool
nir_opt_undef(nir_shader *shader)
{
+ struct undef_options options = {0};
+
+ /* Disallow the undef->NaN transformation only for those shaders where
+ * it's known to break rendering. These are shader source SHA1s printed by
+ * nir_print_shader().
+ */
+ uint32_t shader_sha1s[][SHA1_DIGEST_LENGTH32] = {
+ /* gputest/gimark */
+ {0x9a1af9e2, 0x68f185bf, 0x11fc1257, 0x1102e80b, 0x5ca350fa},
+
+ /* Viewperf13/CATIA_car_01 */
+ {0x4746a4a4, 0xe3b27d27, 0xe6d2b0fb, 0xb7e9ceb3, 0x973e6152}, /* Taillights */
+ {0xc49cc90d, 0xd7208212, 0x726502ea, 0xe1fe62c0, 0xb62fbd1f}, /* Grill */
+ {0xde23f35b, 0xb6fa45ae, 0x96da7e6b, 0x5a6e4a60, 0xce0b6b31}, /* Headlights */
+ {0xdf36242c, 0x0705db59, 0xf1ddac9b, 0xcd1c8466, 0x4c73203b}, /* Rims */
+
+ /* Viewperf13/CATIA_car_04 */
+ {0x631da72a, 0xc971e849, 0xd6489a15, 0xf7c8dddb, 0xe8efd982}, /* Headlights */
+ {0x85984b88, 0xd16b8fee, 0x0d49d97b, 0x5f6cc66e, 0xadcafad9}, /* Rims */
+ {0xad023488, 0x09930735, 0xb0567e58, 0x336dce36, 0xe3c1e448}, /* Tires */
+ {0xdcc4a549, 0x587873fa, 0xeed94361, 0x9a47cbff, 0x846d0167}, /* Windows */
+ {0xfa0074a2, 0xef868430, 0x87935a0c, 0x19bc96be, 0xb5b95c74}, /* Body */
+ };
+
+ for (unsigned i = 0; i < ARRAY_SIZE(shader_sha1s); i++) {
+ if (_mesa_printed_sha1_equal(shader->info.source_sha1, shader_sha1s[i])) {
+ options.disallow_undef_to_nan = true;
+ break;
+ }
+ }
+
return nir_shader_instructions_pass(shader,
nir_opt_undef_instr,
nir_metadata_block_index |
- nir_metadata_dominance,
- NULL);
+ nir_metadata_dominance,
+ &options);
}