2 * Copyright © 2015 Intel Corporation
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
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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:
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
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
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20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
25 #include "nir_builder.h"
26 #include "nir_control_flow.h"
29 void nir_inline_function_impl(struct nir_builder
*b
,
30 const nir_function_impl
*impl
,
33 nir_function_impl
*copy
= nir_function_impl_clone(b
->shader
, impl
);
35 /* Insert a nop at the cursor so we can keep track of where things are as
36 * we add/remove stuff from the CFG.
38 nir_intrinsic_instr
*nop
=
39 nir_intrinsic_instr_create(b
->shader
, nir_intrinsic_nop
);
40 nir_builder_instr_insert(b
, &nop
->instr
);
42 exec_list_append(&b
->impl
->locals
, ©
->locals
);
43 exec_list_append(&b
->impl
->registers
, ©
->registers
);
45 nir_foreach_block(block
, copy
) {
46 nir_foreach_instr_safe(instr
, block
) {
47 switch (instr
->type
) {
48 case nir_instr_type_intrinsic
: {
49 nir_intrinsic_instr
*load
= nir_instr_as_intrinsic(instr
);
50 if (load
->intrinsic
!= nir_intrinsic_load_param
)
53 unsigned param_idx
= nir_intrinsic_param_idx(load
);
54 assert(param_idx
< impl
->function
->num_params
);
55 assert(load
->dest
.is_ssa
);
56 nir_ssa_def_rewrite_uses(&load
->dest
.ssa
,
57 nir_src_for_ssa(params
[param_idx
]));
59 /* Remove any left-over load_param intrinsics because they're soon
60 * to be in another function and therefore no longer valid.
62 nir_instr_remove(&load
->instr
);
66 case nir_instr_type_jump
:
67 /* Returns have to be lowered for this to work */
68 assert(nir_instr_as_jump(instr
)->type
!= nir_jump_return
);
77 /* Pluck the body out of the function and place it here */
79 nir_cf_list_extract(&body
, ©
->body
);
80 nir_cf_reinsert(&body
, nir_before_instr(&nop
->instr
));
82 b
->cursor
= nir_instr_remove(&nop
->instr
);
85 static bool inline_function_impl(nir_function_impl
*impl
, struct set
*inlined
);
88 inline_functions_block(nir_block
*block
, nir_builder
*b
,
91 bool progress
= false;
92 /* This is tricky. We're iterating over instructions in a block but, as
93 * we go, the block and its instruction list are being split into
94 * pieces. However, this *should* be safe since foreach_safe always
95 * stashes the next thing in the iteration. That next thing will
96 * properly get moved to the next block when it gets split, and we
97 * continue iterating there.
99 nir_foreach_instr_safe(instr
, block
) {
100 if (instr
->type
!= nir_instr_type_call
)
105 nir_call_instr
*call
= nir_instr_as_call(instr
);
106 assert(call
->callee
->impl
);
108 /* Make sure that the function we're calling is already inlined */
109 inline_function_impl(call
->callee
->impl
, inlined
);
111 b
->cursor
= nir_instr_remove(&call
->instr
);
113 /* Rewrite all of the uses of the callee's parameters to use the call
114 * instructions sources. In order to ensure that the "load" happens
115 * here and not later (for register sources), we make sure to convert it
116 * to an SSA value first.
118 const unsigned num_params
= call
->num_params
;
119 NIR_VLA(nir_ssa_def
*, params
, num_params
);
120 for (unsigned i
= 0; i
< num_params
; i
++) {
121 params
[i
] = nir_ssa_for_src(b
, call
->params
[i
],
122 call
->callee
->params
[i
].num_components
);
125 nir_inline_function_impl(b
, call
->callee
->impl
, params
);
132 inline_function_impl(nir_function_impl
*impl
, struct set
*inlined
)
134 if (_mesa_set_search(inlined
, impl
))
135 return false; /* Already inlined */
138 nir_builder_init(&b
, impl
);
140 bool progress
= false;
141 nir_foreach_block_safe(block
, impl
) {
142 progress
|= inline_functions_block(block
, &b
, inlined
);
146 /* SSA and register indices are completely messed up now */
147 nir_index_ssa_defs(impl
);
148 nir_index_local_regs(impl
);
150 nir_metadata_preserve(impl
, nir_metadata_none
);
152 nir_metadata_preserve(impl
, nir_metadata_all
);
155 _mesa_set_add(inlined
, impl
);
160 /** A pass to inline all functions in a shader into their callers
162 * For most use-cases, function inlining is a multi-step process. The general
163 * pattern employed by SPIR-V consumers and others is as follows:
165 * 1. nir_lower_variable_initializers(shader, nir_var_function_temp)
167 * This is needed because local variables from the callee are simply added
168 * to the locals list for the caller and the information about where the
169 * constant initializer logically happens is lost. If the callee is
170 * called in a loop, this can cause the variable to go from being
171 * initialized once per loop iteration to being initialized once at the
172 * top of the caller and values to persist from one invocation of the
173 * callee to the next. The simple solution to this problem is to get rid
174 * of constant initializers before function inlining.
176 * 2. nir_lower_returns(shader)
178 * nir_inline_functions assumes that all functions end "naturally" by
179 * execution reaching the end of the function without any return
180 * instructions causing instant jumps to the end. Thanks to NIR being
181 * structured, we can't represent arbitrary jumps to various points in the
182 * program which is what an early return in the callee would have to turn
183 * into when we inline it into the caller. Instead, we require returns to
184 * be lowered which lets us just copy+paste the callee directly into the
187 * 3. nir_inline_functions(shader)
189 * This does the actual function inlining and the resulting shader will
190 * contain no call instructions.
192 * 4. nir_opt_deref(shader)
194 * Most functions contain pointer parameters where the result of a deref
195 * instruction is passed in as a parameter, loaded via a load_param
196 * intrinsic, and then turned back into a deref via a cast. Function
197 * inlining will get rid of the load_param but we are still left with a
198 * cast. Running nir_opt_deref gets rid of the intermediate cast and
199 * results in a whole deref chain again. This is currently required by a
200 * number of optimizations and lowering passes at least for certain
203 * 5. Loop over the functions and delete all but the main entrypoint.
205 * In the Intel Vulkan driver this looks like this:
207 * foreach_list_typed_safe(nir_function, func, node, &nir->functions) {
208 * if (func != entry_point)
209 * exec_node_remove(&func->node);
211 * assert(exec_list_length(&nir->functions) == 1);
213 * While nir_inline_functions does get rid of all call instructions, it
214 * doesn't get rid of any functions because it doesn't know what the "root
215 * function" is. Instead, it's up to the individual driver to know how to
216 * decide on a root function and delete the rest. With SPIR-V,
217 * spirv_to_nir returns the root function and so we can just use == whereas
218 * with GL, you may have to look for a function named "main".
220 * 6. nir_lower_variable_initializers(shader, ~nir_var_function_temp)
222 * Lowering constant initializers on inputs, outputs, global variables,
223 * etc. requires that we know the main entrypoint so that we know where to
224 * initialize them. Otherwise, we would have to assume that anything
225 * could be a main entrypoint and initialize them at the start of every
226 * function but that would clearly be wrong if any of those functions were
227 * ever called within another function. Simply requiring a single-
228 * entrypoint function shader is the best way to make it well-defined.
231 nir_inline_functions(nir_shader
*shader
)
233 struct set
*inlined
= _mesa_pointer_set_create(NULL
);
234 bool progress
= false;
236 nir_foreach_function(function
, shader
) {
238 progress
= inline_function_impl(function
->impl
, inlined
) || progress
;
241 _mesa_set_destroy(inlined
, NULL
);