[Mesa-dev] [RFC] nir: add lowering stage for user-clip-planes
Rob Clark
robdclark at gmail.com
Thu Sep 10 14:39:02 PDT 2015
From: Rob Clark <robclark at freedesktop.org>
So this is basically working as a lowering pass for handling user-clip-
planes, and frag-shader emulation of CLIPDIST for hardware that needs
to handle this in the shader.
For user-clip-planes, instructions are inserted to calculate CLIPDIST
in the VS. And in both cases, discard_if's are inserted in FS to
handle the clipping.
NOTE: This currently requires a bit of a hack in nir_validate, which
is unhappy about things like:
decl_var uniform vec4[10] uniform_0 (0, 0)
decl_var shader_out vec4 out_0 (0, 0)
decl_var shader_out vec4 clipdist_1 (17, 1)
decl_var shader_out vec4 clipdist_2 (18, 2)
decl_overload main returning void
impl main {
block block_0:
/* preds: */
...
/* succs: block_1 */
block block_1:
/* preds: block_0 */
... inserted CLIPDIST calculations ...
/* succs: block_2 */
block block_2:
}
The thing is, repurposing the end_block and creating a new end_block,
without having to consider all the different potential successors,
seems like by far the easiest way to insert code at the end of a
shader. So probably useful in other cases. (I do something similar
internally in ir3 for transform-feedback).
Seems like the easiest thing would be to relax the restriction in
nir_validate, but I'm not sure if this will break other assumptions
elsewhere.
TODO: sort out hack in nir_validate, reindent, etc.
---
src/glsl/Makefile.sources | 1 +
src/glsl/nir/nir.h | 3 +
src/glsl/nir/nir_lower_clip.c | 346 ++++++++++++++++++++++++++++++++++++++++++
src/glsl/nir/nir_validate.c | 3 +-
4 files changed, 351 insertions(+), 2 deletions(-)
create mode 100644 src/glsl/nir/nir_lower_clip.c
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index da7fdf9..5d98b7b 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -35,6 +35,7 @@ NIR_FILES = \
nir/nir_live_variables.c \
nir/nir_lower_alu_to_scalar.c \
nir/nir_lower_atomics.c \
+ nir/nir_lower_clip.c \
nir/nir_lower_global_vars_to_local.c \
nir/nir_lower_load_const_to_scalar.c \
nir/nir_lower_locals_to_regs.c \
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 2ba7731..8544140 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1811,6 +1811,9 @@ void nir_lower_system_values(nir_shader *shader);
void nir_lower_tex_projector(nir_shader *shader);
void nir_lower_idiv(nir_shader *shader);
+void nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables);
+void nir_lower_clip_fs(nir_shader *shader, unsigned ucp_enables);
+
void nir_lower_atomics(nir_shader *shader);
void nir_lower_to_source_mods(nir_shader *shader);
diff --git a/src/glsl/nir/nir_lower_clip.c b/src/glsl/nir/nir_lower_clip.c
new file mode 100644
index 0000000..54ebe7b
--- /dev/null
+++ b/src/glsl/nir/nir_lower_clip.c
@@ -0,0 +1,346 @@
+/*
+ * Copyright © 2015 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.
+ *
+ * Authors:
+ * Rob Clark <robclark at freedesktop.org>
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+#define MAX_CLIP_PLANES 8
+
+/* Generates the lowering code for user-clip-planes, generating CLIPDIST
+ * from UCP[n] + CLIPVERTEX or POSITION. Additionally, an optional pass
+ * for fragment shaders to insert conditional kill's based on the inter-
+ * polated CLIPDIST
+ *
+ * NOTE: should be run after nir_lower_outputs_to_temporaries() (or at
+ * least in scenarios where you can count on each output written once
+ * and only once).
+ */
+
+
+static nir_variable *
+create_clipdist_var(nir_shader *shader, unsigned drvloc,
+ bool output, gl_varying_slot slot)
+{
+ nir_variable *var = rzalloc(shader, nir_variable);
+
+ var->data.driver_location = drvloc;
+ var->type = glsl_vec4_type();
+ var->data.mode = output ? nir_var_shader_out : nir_var_shader_in;
+ var->name = ralloc_asprintf(var, "clipdist_%d", drvloc);
+ var->data.index = 0;
+ var->data.location = slot;
+
+ if (output) {
+ exec_list_push_tail(&shader->outputs, &var->node);
+ } else {
+ exec_list_push_tail(&shader->inputs, &var->node);
+ }
+ return var;
+}
+
+static void
+store_clipdist_output(nir_builder *b, nir_variable *out, nir_ssa_def **val)
+{
+ nir_intrinsic_instr *store;
+
+ store = nir_intrinsic_instr_create(b->shader, nir_intrinsic_store_output);
+ store->num_components = 4;
+ store->const_index[0] = out->data.driver_location;
+ store->src[0].ssa = nir_vec4(b, val[0], val[1], val[2], val[3]);
+ store->src[0].is_ssa = true;
+ nir_builder_instr_insert(b, &store->instr);
+}
+
+static void
+load_clipdist_input(nir_builder *b, nir_variable *in, nir_ssa_def **val)
+{
+ nir_intrinsic_instr *load;
+
+ load = nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_input);
+ load->num_components = 4;
+ load->const_index[0] = in->data.driver_location;
+ nir_ssa_dest_init(&load->instr, &load->dest, 4, NULL);
+ nir_builder_instr_insert(b, &load->instr);
+
+ val[0] = nir_channel(b, &load->dest.ssa, 0);
+ val[1] = nir_channel(b, &load->dest.ssa, 1);
+ val[2] = nir_channel(b, &load->dest.ssa, 2);
+ val[3] = nir_channel(b, &load->dest.ssa, 3);
+}
+
+struct find_output_state {
+ unsigned drvloc;
+ nir_ssa_def *def;
+};
+
+static bool
+find_output_in_block(nir_block *block, void *void_state)
+{
+ struct find_output_state *state = void_state;
+ nir_foreach_instr(block, instr) {
+
+ if (instr->type == nir_instr_type_intrinsic) {
+ nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+ if ((intr->intrinsic == nir_intrinsic_store_output) &&
+ intr->const_index[0] == state->drvloc) {
+ assert(state->def == NULL);
+ assert(intr->src[0].is_ssa);
+ state->def = intr->src[0].ssa;
+ }
+ }
+
+#if !defined(DEBUG)
+ /* for debug builds, scan entire shader to assert
+ * if output is written multiple times. For release
+ * builds just assume all is well and bail when we
+ * find first:
+ */
+ if (state->def)
+ return false;
+#endif
+ }
+
+ return true;
+}
+
+/* TODO: maybe this would be a useful helper?
+ * NOTE: assumes each output is written exactly once (and unconditionally)
+ * so if needed nir_lower_outputs_to_temporaries()
+ */
+static nir_ssa_def *
+find_output(nir_shader *shader, unsigned drvloc)
+{
+ struct find_output_state state = {
+ .drvloc = drvloc,
+ };
+
+ nir_foreach_overload(shader, overload) {
+ if (overload->impl) {
+ nir_foreach_block_reverse(overload->impl,
+ find_output_in_block, &state);
+ }
+ }
+
+ return state.def;
+}
+
+/*
+ * VS lowering
+ */
+
+static void
+lower_clip_vs(nir_function_impl *impl, unsigned ucp_enables,
+ nir_ssa_def *cv, nir_variable **out)
+{
+ nir_ssa_def *clipdist[MAX_CLIP_PLANES];
+ nir_builder b;
+
+ nir_builder_init(&b, impl);
+
+ /* Push original end_block to end of body. Since all other
+ * blocks flow into end_block, it is a convenient place to
+ * insert our new clipdist calculations. A new empty
+ * end_block is created:
+ *
+ * NOTE: by default nir_validate is unhappy about formations
+ * such as
+ *
+ * block block_0:
+ * // preds:
+ * ...
+ * // succs: block_1
+ * block block_1:
+ * // preds: block_0
+ * ...
+ * // succs: block_2
+ * block block_2:
+ * ...
+ */
+ exec_list_push_tail(&impl->body, &impl->end_block->cf_node.node);
+ nir_block *new_end_block = nir_block_create(b.shader);
+ impl->end_block->successors[0] = new_end_block;
+ _mesa_set_add(new_end_block->predecessors, impl->end_block);
+ impl->end_block = new_end_block;
+ b.cursor = nir_after_cf_list(&impl->body);
+
+ for (int plane = 0; plane < MAX_CLIP_PLANES; plane++) {
+ if (ucp_enables & (1 << plane)) {
+ nir_intrinsic_instr *ucp;
+
+ /* insert intrinsic to fetch ucp[plane]: */
+ ucp = nir_intrinsic_instr_create(b.shader,
+ nir_intrinsic_load_user_clip_plane);
+ ucp->num_components = 4;
+ ucp->const_index[0] = plane;
+ nir_ssa_dest_init(&ucp->instr, &ucp->dest, 4, NULL);
+ nir_builder_instr_insert(&b, &ucp->instr);
+
+ /* calculate clipdist[plane] - dot(ucp, cv): */
+ clipdist[plane] = nir_fdot3(&b, &ucp->dest.ssa, cv);
+ } else {
+ /* 0.0 == don't-clip == disabled: */
+ clipdist[plane] = nir_imm_float(&b, 0.0);
+ }
+ }
+
+ if (ucp_enables & 0x0f)
+ store_clipdist_output(&b, out[0], &clipdist[0]);
+ if (ucp_enables & 0xf0)
+ store_clipdist_output(&b, out[1], &clipdist[4]);
+
+ nir_metadata_preserve(impl, nir_metadata_dominance);
+}
+
+/* ucp_enables is bitmask of enabled ucp's. Actual ucp values are
+ * passed in to shader via user_clip_plane system-values
+ */
+void
+nir_lower_clip_vs(nir_shader *shader, unsigned ucp_enables)
+{
+ int clipvertex = -1;
+ int position = -1;
+ int maxloc = -1;
+ nir_ssa_def *cv;
+ nir_variable *out[2];
+
+ if (!ucp_enables)
+ return;
+
+ /* find clipvertex/position outputs: */
+ foreach_list_typed(nir_variable, var, node, &shader->outputs) {
+ int loc = var->data.driver_location;
+
+ /* keep track of last used driver-location.. we'll be
+ * appending CLIP_DIST0/CLIP_DIST1 after last existing
+ * output:
+ */
+ maxloc = MAX2(maxloc, loc);
+
+ switch (var->data.location) {
+ case VARYING_SLOT_POS:
+ position = loc;
+ break;
+ case VARYING_SLOT_CLIP_VERTEX:
+ clipvertex = loc;
+ break;
+ case VARYING_SLOT_CLIP_DIST0:
+ case VARYING_SLOT_CLIP_DIST1:
+ /* if shader is already writing CLIPDIST, then
+ * there should be no user-clip-planes to deal
+ * with.
+ */
+ return;
+ }
+ }
+
+ if (clipvertex != -1)
+ cv = find_output(shader, clipvertex);
+ else if (position != -1)
+ cv = find_output(shader, position);
+ else
+ return;
+
+ /* insert CLIPDIST outputs: */
+ if (ucp_enables & 0x0f)
+ out[0] = create_clipdist_var(shader, ++maxloc, true, VARYING_SLOT_CLIP_DIST0);
+ if (ucp_enables & 0xf0)
+ out[1] = create_clipdist_var(shader, ++maxloc, true, VARYING_SLOT_CLIP_DIST1);
+
+ nir_foreach_overload(shader, overload) {
+ if (!strcmp(overload->function->name, "main"))
+ lower_clip_vs(overload->impl, ucp_enables, cv, out);
+ }
+}
+
+/*
+ * FS lowering
+ */
+
+static void
+lower_clip_fs(nir_function_impl *impl, unsigned ucp_enables,
+ nir_variable **in)
+{
+ nir_ssa_def *clipdist[MAX_CLIP_PLANES];
+ nir_builder b;
+
+ nir_builder_init(&b, impl);
+ b.cursor = nir_before_cf_list(&impl->body);
+
+ if (ucp_enables & 0x0f)
+ load_clipdist_input(&b, in[0], &clipdist[0]);
+ if (ucp_enables & 0xf0)
+ load_clipdist_input(&b, in[1], &clipdist[4]);
+
+ for (int plane = 0; plane < MAX_CLIP_PLANES; plane++) {
+ if (ucp_enables & (1 << plane)) {
+ nir_intrinsic_instr *discard;
+ nir_ssa_def *cond;
+
+ cond = nir_flt(&b, clipdist[plane], nir_imm_float(&b, 0.0));
+
+ discard = nir_intrinsic_instr_create(b.shader,
+ nir_intrinsic_discard_if);
+ discard->src[0] = nir_src_for_ssa(cond);
+ nir_builder_instr_insert(&b, &discard->instr);
+ }
+ }
+}
+
+/* insert conditional kill based on interpolated CLIPDIST
+ */
+void
+nir_lower_clip_fs(nir_shader *shader, unsigned ucp_enables)
+{
+ nir_variable *in[2];
+ int maxloc = -1;
+
+ if (!ucp_enables)
+ return;
+
+ foreach_list_typed(nir_variable, var, node, &shader->inputs) {
+ int loc = var->data.driver_location;
+
+ /* keep track of last used driver-location.. we'll be
+ * appending CLIP_DIST0/CLIP_DIST1 after last existing
+ * input:
+ */
+ maxloc = MAX2(maxloc, loc);
+ }
+
+ /* The shader won't normally have CLIPDIST inputs, so we
+ * must add our own:
+ */
+ /* insert CLIPDIST outputs: */
+ if (ucp_enables & 0x0f)
+ in[0] = create_clipdist_var(shader, ++maxloc, false, VARYING_SLOT_CLIP_DIST0);
+ if (ucp_enables & 0xf0)
+ in[1] = create_clipdist_var(shader, ++maxloc, false, VARYING_SLOT_CLIP_DIST1);
+
+ nir_foreach_overload(shader, overload) {
+ if (!strcmp(overload->function->name, "main"))
+ lower_clip_fs(overload->impl, ucp_enables, in);
+ }
+}
diff --git a/src/glsl/nir/nir_validate.c b/src/glsl/nir/nir_validate.c
index 9938c0e..f682575 100644
--- a/src/glsl/nir/nir_validate.c
+++ b/src/glsl/nir/nir_validate.c
@@ -667,8 +667,7 @@ validate_block(nir_block *block, validate_state *state)
nir_if_first_then_node(if_stmt));
assert(&block->successors[1]->cf_node ==
nir_if_first_else_node(if_stmt));
- } else {
- assert(next->type == nir_cf_node_loop);
+ } else if (next->type == nir_cf_node_loop) {
nir_loop *loop = nir_cf_node_as_loop(next);
assert(&block->successors[0]->cf_node ==
nir_loop_first_cf_node(loop));
--
2.4.3
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