<div dir="ltr"><div>I am not really that much familiar with nir, so I apologize if what I write below is wrong.</div><div> </div>What if we had something like:<div> </div><div>a = 0;</div><div>if (x) {</div><div> discard_if(y);</div><div> a = 1;</div><div>}</div><div> </div><div>Then if (x && !y), we must not discard and both at the same time set a to 1. Your transformation would probably change it to:</div><div> </div><div>a = 0;</div><div>discard_if(x && y);</div><div> </div><div>Which is incorrect.</div><div> </div><div>I think you have to ensure (if the intrinsic is discard_if) that discard_if is the only instruction inside the then block. Or just remove the intrinsic from the then block and leave the rest of the if alone.</div><div> </div><div>Regards,</div><div>Gustaw</div></div><div class="gmail_extra"> <div class="gmail_quote">2016-11-03 4:28 GMT+01:00 Dave Airlie <<a href="mailto:airlied@gmail.com" target="_blank">airlied@gmail.com</a>>: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">From: Dave Airlie <<a href="mailto:airlied@redhat.com">airlied@redhat.com</a>> This is ported from GLSL and converts if (cond) discard; into discard_if(cond); This removes a block, but also is needed by radv to workaround a bug in the LLVM backend. v2: handle if (a) discard_if(b) (nha) cleanup and drop pointless loop (Matt) make sure there are no dependent phis (Eric) Signed-off-by: Dave Airlie <<a href="mailto:airlied@redhat.com">airlied@redhat.com</a>> --- src/compiler/Makefile.sources | 1 + src/compiler/nir/nir.h | 2 + src/compiler/nir/nir_opt_conditional_discard.c | 124 +++++++++++++++++++++++++ 3 files changed, 127 insertions(+) create mode 100644 src/compiler/nir/nir_opt_conditional_discard.c diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources index 669c499..b710cbd 100644 --- a/src/compiler/Makefile.sources +++ b/src/compiler/Makefile.sources @@ -228,6 +228,7 @@ NIR_FILES = \ nir/nir_metadata.c \ nir/nir_move_vec_src_uses_to_dest.c \ nir/nir_normalize_cubemap_coords.c \ + nir/nir_opt_conditional_discard.c \ nir/nir_opt_constant_folding.c \ nir/nir_opt_copy_propagate.c \ nir/nir_opt_cse.c \ diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h index 9264763..2a77139 100644 --- a/src/compiler/nir/nir.h +++ b/src/compiler/nir/nir.h @@ -2531,6 +2531,8 @@ bool nir_opt_remove_phis(nir_shader *shader); bool nir_opt_undef(nir_shader *shader); +bool nir_opt_conditional_discard(nir_shader *shader); + void nir_sweep(nir_shader *shader); nir_intrinsic_op nir_intrinsic_from_system_value(gl_system_value val); diff --git a/src/compiler/nir/nir_opt_conditional_discard.c b/src/compiler/nir/nir_opt_conditional_discard.c new file mode 100644 index 0000000..2259a14 --- /dev/null +++ b/src/compiler/nir/nir_opt_conditional_discard.c @@ -0,0 +1,124 @@ +/* + * Copyright © 2016 Red Hat + * + * 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" + +/** @file nir_opt_conditional_discard.c + * + * Handles optimization of lowering if (cond) discard to discard_if(cond). + */ + +static bool +nir_opt_conditional_discard_block(nir_block *block, void *mem_ctx) +{ + nir_builder bld; + + if (nir_cf_node_is_first(&block->cf_node)) + return false; + + nir_cf_node *prev_node = nir_cf_node_prev(&block->cf_node); + if (prev_node->type != nir_cf_node_if) + return false; + + nir_if *if_stmt = nir_cf_node_as_if(prev_node); + nir_block *then_block = nir_if_first_then_block(if_stmt); + nir_block *else_block = nir_if_first_else_block(if_stmt); + + /* check there is only one else block and it is empty */ + if (nir_if_last_else_block(if_stmt) != else_block) + return false; + if (!exec_list_is_empty(&else_block->instr_list)) + return false; + + /* check there is only one then block and it has instructions in it */ + if (nir_if_last_then_block(if_stmt) != then_block) + return false; + if (exec_list_is_empty(&then_block->instr_list)) + return false; + + /* + * make sure no subsequent phi nodes point at this if. + */ + nir_block *after = nir_cf_node_as_block(nir_cf_node_next(&if_stmt->cf_node)); + nir_foreach_instr_safe(instr, after) { + if (instr->type != nir_instr_type_phi) + break; + nir_phi_instr *phi = nir_instr_as_phi(instr); + + nir_foreach_phi_src(phi_src, phi) { + if (phi_src->pred == then_block || + phi_src->pred == else_block) + return false; + } + } + + /* Get the first instruction in the then block and confirm it is + * a discard or a discard_if + */ + nir_instr *instr = nir_block_first_instr(then_block); + if (instr->type != nir_instr_type_intrinsic) + return false; + + nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr); + if (intrin->intrinsic != nir_intrinsic_discard && + intrin->intrinsic != nir_intrinsic_discard_if) + return false; + + nir_src cond; + + nir_builder_init(&bld, mem_ctx); + + if (intrin->intrinsic == nir_intrinsic_discard) + cond = if_stmt->condition; + else + cond = nir_src_for_ssa(nir_iand(&bld, + nir_ssa_for_src(&bld, if_stmt->condition, 1), + nir_ssa_for_src(&bld, intrin->src[0], 1))); + + nir_intrinsic_instr *discard_if = + nir_intrinsic_instr_create(mem_ctx, nir_intrinsic_discard_if); + nir_src_copy(&discard_if->src[0], &cond, discard_if); + + nir_instr_insert_before_cf(prev_node, &discard_if->instr); + nir_instr_remove(&intrin->instr); + nir_cf_node_remove(&if_stmt->cf_node); + + return true; +} + +bool +nir_opt_conditional_discard(nir_shader *shader) +{ + bool progress = false; + + nir_foreach_function(function, shader) { + if (function->impl) { + void *mem_ctx = ralloc_parent(function->impl); + nir_foreach_block_safe(block, function->impl) { + progress |= nir_opt_conditional_discard_block(block, mem_ctx); + } + } + } + return progress; +} -- 2.7.4 _______________________________________________ mesa-dev mailing list <a href="mailto:mesa-dev@lists.freedesktop.org">mesa-dev@lists.freedesktop.org</a> <a href="https://lists.freedesktop.org/mailman/listinfo/mesa-dev" rel="noreferrer" target="_blank">https://lists.freedesktop.org/mailman/listinfo/mesa-dev</a> </blockquote></div> </div>