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      1 /*
      2  * Copyright  2015 Broadcom
      3  *
      4  * Permission is hereby granted, free of charge, to any person obtaining a
      5  * copy of this software and associated documentation files (the "Software"),
      6  * to deal in the Software without restriction, including without limitation
      7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
      8  * and/or sell copies of the Software, and to permit persons to whom the
      9  * Software is furnished to do so, subject to the following conditions:
     10  *
     11  * The above copyright notice and this permission notice (including the next
     12  * paragraph) shall be included in all copies or substantial portions of the
     13  * Software.
     14  *
     15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
     18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
     21  * IN THE SOFTWARE.
     22  */
     23 
     24 #include "util/macros.h"
     25 #include "nir.h"
     26 #include "nir_builder.h"
     27 
     28 /** @file nir_lower_load_const_to_scalar.c
     29  *
     30  * Replaces vector nir_load_const instructions with a series of loads and a
     31  * vec[234] to reconstruct the original vector (on the assumption that
     32  * nir_lower_alu_to_scalar() will then be used to split it up).
     33  *
     34  * This gives NIR a chance to CSE more operations on a scalar shader, when the
     35  * same value was used in different vector contant loads.
     36  */
     37 
     38 static void
     39 lower_load_const_instr_scalar(nir_load_const_instr *lower)
     40 {
     41    if (lower->def.num_components == 1)
     42       return;
     43 
     44    nir_builder b;
     45    nir_builder_init(&b, nir_cf_node_get_function(&lower->instr.block->cf_node));
     46    b.cursor = nir_before_instr(&lower->instr);
     47 
     48    /* Emit the individual loads. */
     49    nir_ssa_def *loads[4];
     50    for (unsigned i = 0; i < lower->def.num_components; i++) {
     51       nir_load_const_instr *load_comp =
     52          nir_load_const_instr_create(b.shader, 1, lower->def.bit_size);
     53       if (lower->def.bit_size == 64)
     54          load_comp->value.f64[0] = lower->value.f64[i];
     55       else
     56          load_comp->value.u32[0] = lower->value.u32[i];
     57       assert(lower->def.bit_size == 64 || lower->def.bit_size == 32);
     58       nir_builder_instr_insert(&b, &load_comp->instr);
     59       loads[i] = &load_comp->def;
     60    }
     61 
     62    /* Batch things back together into a vector. */
     63    nir_ssa_def *vec = nir_vec(&b, loads, lower->def.num_components);
     64 
     65    /* Replace the old load with a reference to our reconstructed vector. */
     66    nir_ssa_def_rewrite_uses(&lower->def, nir_src_for_ssa(vec));
     67    nir_instr_remove(&lower->instr);
     68 }
     69 
     70 static void
     71 nir_lower_load_const_to_scalar_impl(nir_function_impl *impl)
     72 {
     73    nir_foreach_block(block, impl) {
     74       nir_foreach_instr_safe(instr, block) {
     75          if (instr->type == nir_instr_type_load_const)
     76             lower_load_const_instr_scalar(nir_instr_as_load_const(instr));
     77       }
     78    }
     79 }
     80 
     81 void
     82 nir_lower_load_const_to_scalar(nir_shader *shader)
     83 {
     84    nir_foreach_function(function, shader) {
     85       if (function->impl)
     86          nir_lower_load_const_to_scalar_impl(function->impl);
     87    }
     88 }
     89