/* * Copyright © 2015 Intel Corporation * * 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. */ #include "nir.h" #include "nir_builder.h" #include "nir_control_flow.h" #include "nir_vla.h" static bool inline_function_impl(nir_function_impl *impl, struct set *inlined); static bool inline_functions_block(nir_block *block, nir_builder *b, struct set *inlined) { bool progress = false; /* This is tricky. We're iterating over instructions in a block but, as * we go, the block and its instruction list are being split into * pieces. However, this *should* be safe since foreach_safe always * stashes the next thing in the iteration. That next thing will * properly get moved to the next block when it gets split, and we * continue iterating there. */ nir_foreach_instr_safe(instr, block) { if (instr->type != nir_instr_type_call) continue; progress = true; nir_call_instr *call = nir_instr_as_call(instr); assert(call->callee->impl); inline_function_impl(call->callee->impl, inlined); nir_function_impl *callee_copy = nir_function_impl_clone(call->callee->impl); callee_copy->function = call->callee; exec_list_append(&b->impl->locals, &callee_copy->locals); exec_list_append(&b->impl->registers, &callee_copy->registers); b->cursor = nir_before_instr(&call->instr); /* Rewrite all of the uses of the callee's parameters to use the call * instructions sources. In order to ensure that the "load" happens * here and not later (for register sources), we make sure to convert it * to an SSA value first. */ const unsigned num_params = call->num_params; NIR_VLA(nir_ssa_def *, params, num_params); for (unsigned i = 0; i < num_params; i++) { params[i] = nir_ssa_for_src(b, call->params[i], call->callee->params[i].num_components); } nir_foreach_block(block, callee_copy) { nir_foreach_instr_safe(instr, block) { if (instr->type != nir_instr_type_intrinsic) continue; nir_intrinsic_instr *load = nir_instr_as_intrinsic(instr); if (load->intrinsic != nir_intrinsic_load_param) continue; unsigned param_idx = nir_intrinsic_param_idx(load); assert(param_idx < num_params); assert(load->dest.is_ssa); nir_ssa_def_rewrite_uses(&load->dest.ssa, nir_src_for_ssa(params[param_idx])); /* Remove any left-over load_param intrinsics because they're soon * to be in another function and therefore no longer valid. */ nir_instr_remove(&load->instr); } } /* Pluck the body out of the function and place it here */ nir_cf_list body; nir_cf_list_extract(&body, &callee_copy->body); nir_cf_reinsert(&body, b->cursor); nir_instr_remove(&call->instr); } return progress; } static bool inline_function_impl(nir_function_impl *impl, struct set *inlined) { if (_mesa_set_search(inlined, impl)) return false; /* Already inlined */ nir_builder b; nir_builder_init(&b, impl); bool progress = false; nir_foreach_block_safe(block, impl) { progress |= inline_functions_block(block, &b, inlined); } if (progress) { /* SSA and register indices are completely messed up now */ nir_index_ssa_defs(impl); nir_index_local_regs(impl); nir_metadata_preserve(impl, nir_metadata_none); } _mesa_set_add(inlined, impl); return progress; } /** A pass to inline all functions in a shader into their callers * * For most use-cases, function inlining is a multi-step process. The general * pattern employed by SPIR-V consumers and others is as follows: * * 1. nir_lower_constant_initializers(shader, nir_var_function) * * This is needed because local variables from the callee are simply added * to the locals list for the caller and the information about where the * constant initializer logically happens is lost. If the callee is * called in a loop, this can cause the variable to go from being * initialized once per loop iteration to being initialized once at the * top of the caller and values to persist from one invocation of the * callee to the next. The simple solution to this problem is to get rid * of constant initializers before function inlining. * * 2. nir_lower_returns(shader) * * nir_inline_functions assumes that all functions end "naturally" by * execution reaching the end of the function without any return * instructions causing instant jumps to the end. Thanks to NIR being * structured, we can't represent arbitrary jumps to various points in the * program which is what an early return in the callee would have to turn * into when we inline it into the caller. Instead, we require returns to * be lowered which lets us just copy+paste the callee directly into the * caller. * * 3. nir_inline_functions(shader) * * This does the actual function inlining and the resulting shader will * contain no call instructions. * * 4. nir_opt_deref(shader) * * Most functions contain pointer parameters where the result of a deref * instruction is passed in as a parameter, loaded via a load_param * intrinsic, and then turned back into a deref via a cast. Function * inlining will get rid of the load_param but we are still left with a * cast. Running nir_opt_deref gets rid of the intermediate cast and * results in a whole deref chain again. This is currently required by a * number of optimizations and lowering passes at least for certain * variable modes. * * 5. Loop over the functions and delete all but the main entrypoint. * * In the Intel Vulkan driver this looks like this: * * foreach_list_typed_safe(nir_function, func, node, &nir->functions) { * if (func != entry_point) * exec_node_remove(&func->node); * } * assert(exec_list_length(&nir->functions) == 1); * * While nir_inline_functions does get rid of all call instructions, it * doesn't get rid of any functions because it doesn't know what the "root * function" is. Instead, it's up to the individual driver to know how to * decide on a root function and delete the rest. With SPIR-V, * spirv_to_nir returns the root function and so we can just use == whereas * with GL, you may have to look for a function named "main". * * 6. nir_lower_constant_initializers(shader, ~nir_var_function) * * Lowering constant initializers on inputs, outputs, global variables, * etc. requires that we know the main entrypoint so that we know where to * initialize them. Otherwise, we would have to assume that anything * could be a main entrypoint and initialize them at the start of every * function but that would clearly be wrong if any of those functions were * ever called within another function. Simply requiring a single- * entrypoint function shader is the best way to make it well-defined. */ bool nir_inline_functions(nir_shader *shader) { struct set *inlined = _mesa_set_create(NULL, _mesa_hash_pointer, _mesa_key_pointer_equal); bool progress = false; nir_foreach_function(function, shader) { if (function->impl) progress = inline_function_impl(function->impl, inlined) || progress; } _mesa_set_destroy(inlined, NULL); return progress; }