Home | History | Annotate | Download | only in nir 
      1 /*
      2  * Copyright  2016 Intel Corporation
      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 "nir.h"
     25 #include "nir_phi_builder.h"
     26 
     27 struct repair_ssa_state {
     28    nir_function_impl *impl;
     29 
     30    BITSET_WORD *def_set;
     31    struct nir_phi_builder *phi_builder;
     32 
     33    bool progress;
     34 };
     35 
     36 /* Get ready to build a phi and return the builder */
     37 static struct nir_phi_builder *
     38 prep_build_phi(struct repair_ssa_state *state)
     39 {
     40    const unsigned num_words = BITSET_WORDS(state->impl->num_blocks);
     41 
     42    /* We create the phi builder on-demand. */
     43    if (state->phi_builder == NULL) {
     44       state->phi_builder = nir_phi_builder_create(state->impl);
     45       state->def_set = ralloc_array(NULL, BITSET_WORD, num_words);
     46    }
     47 
     48    /* We're going to build a phi.  That's progress. */
     49    state->progress = true;
     50 
     51    /* Set the defs set to empty */
     52    memset(state->def_set, 0, num_words * sizeof(*state->def_set));
     53 
     54    return state->phi_builder;
     55 }
     56 
     57 static nir_block *
     58 get_src_block(nir_src *src)
     59 {
     60    if (src->parent_instr->type == nir_instr_type_phi) {
     61       return exec_node_data(nir_phi_src, src, src)->pred;
     62    } else {
     63       return src->parent_instr->block;
     64    }
     65 }
     66 
     67 static bool
     68 repair_ssa_def(nir_ssa_def *def, void *void_state)
     69 {
     70    struct repair_ssa_state *state = void_state;
     71 
     72    bool is_valid = true;
     73    nir_foreach_use(src, def) {
     74       if (!nir_block_dominates(def->parent_instr->block, get_src_block(src))) {
     75          is_valid = false;
     76          break;
     77       }
     78    }
     79 
     80    if (is_valid)
     81       return true;
     82 
     83    struct nir_phi_builder *pb = prep_build_phi(state);
     84 
     85    BITSET_SET(state->def_set, def->parent_instr->block->index);
     86 
     87    struct nir_phi_builder_value *val =
     88       nir_phi_builder_add_value(pb, def->num_components, def->bit_size,
     89                                 state->def_set);
     90 
     91    nir_phi_builder_value_set_block_def(val, def->parent_instr->block, def);
     92 
     93    nir_foreach_use_safe(src, def) {
     94       nir_block *src_block = get_src_block(src);
     95       if (!nir_block_dominates(def->parent_instr->block, src_block)) {
     96          nir_instr_rewrite_src(src->parent_instr, src, nir_src_for_ssa(
     97             nir_phi_builder_value_get_block_def(val, src_block)));
     98       }
     99    }
    100 
    101    return true;
    102 }
    103 
    104 bool
    105 nir_repair_ssa_impl(nir_function_impl *impl)
    106 {
    107    struct repair_ssa_state state;
    108 
    109    state.impl = impl;
    110    state.phi_builder = NULL;
    111    state.progress = false;
    112 
    113    nir_metadata_require(impl, nir_metadata_block_index |
    114                               nir_metadata_dominance);
    115 
    116    nir_foreach_block(block, impl) {
    117       nir_foreach_instr_safe(instr, block) {
    118          nir_foreach_ssa_def(instr, repair_ssa_def, &state);
    119       }
    120    }
    121 
    122    if (state.progress)
    123       nir_metadata_preserve(impl, nir_metadata_block_index |
    124                                   nir_metadata_dominance);
    125 
    126    if (state.phi_builder) {
    127       nir_phi_builder_finish(state.phi_builder);
    128       ralloc_free(state.def_set);
    129    }
    130 
    131    return state.progress;
    132 }
    133 
    134 /** This pass can be used to repair SSA form in a shader.
    135  *
    136  * Sometimes a transformation (such as return lowering) will have to make
    137  * changes to a shader which, while still correct, break some of NIR's SSA
    138  * invariants.  This pass will insert ssa_undefs and phi nodes as needed to
    139  * get the shader back into SSA that the validator will like.
    140  */
    141 bool
    142 nir_repair_ssa(nir_shader *shader)
    143 {
    144    bool progress = false;
    145 
    146    nir_foreach_function(function, shader) {
    147       if (function->impl)
    148          progress = nir_repair_ssa_impl(function->impl) || progress;
    149    }
    150 
    151    return progress;
    152 }
    153