[v3,1/2] nir: Add nir_lower_viewport_transform

Submitted by Alyssa Rosenzweig on April 12, 2019, 11:46 p.m.

Details

Message ID 20190412234655.6742-1-alyssa@rosenzweig.io
State New
Headers show
Series "Series without cover letter" ( rev: 1 ) in Mesa

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Commit Message

Alyssa Rosenzweig April 12, 2019, 11:46 p.m.
On Mali hardware (supported by Panfrost and Lima), the fixed-function
transformation from world-space to screen-space coordinates is done in
the vertex shader prior to writing out the gl_Position varying, rather
than in dedicated hardware. This commit adds a shared NIR pass for
implementing coordinate transformation and lowering gl_Position writes
into screen-space gl_Position writes.

v2: Run directly on derefs before io/vars are lowered to cleanup the
code substantially. Thank you to Qiang for this suggestion!

v3: Bikeshed continues.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Suggested-by: Qiang Yu <yuq825@gmail.com>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Eric Anholt <eric@anholt.net>
---
 src/compiler/nir/meson.build                  |   1 +
 src/compiler/nir/nir.h                        |   1 +
 .../nir/nir_lower_viewport_transform.c        | 101 ++++++++++++++++++
 3 files changed, 103 insertions(+)
 create mode 100644 src/compiler/nir/nir_lower_viewport_transform.c

Patch hide | download patch | download mbox

diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
index c65f2ff62ff..c274361bdc4 100644
--- a/src/compiler/nir/meson.build
+++ b/src/compiler/nir/meson.build
@@ -151,6 +151,7 @@  files_libnir = files(
   'nir_lower_vars_to_ssa.c',
   'nir_lower_var_copies.c',
   'nir_lower_vec_to_movs.c',
+  'nir_lower_viewport_transform.c',
   'nir_lower_wpos_center.c',
   'nir_lower_wpos_ytransform.c',
   'nir_lower_bit_size.c',
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index bc72d8f83f5..0f6ed734efa 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -3124,6 +3124,7 @@  void nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask);
 void nir_lower_io_to_scalar_early(nir_shader *shader, nir_variable_mode mask);
 bool nir_lower_io_to_vector(nir_shader *shader, nir_variable_mode mask);
 
+void nir_lower_viewport_transform(nir_shader *shader);
 bool nir_lower_uniforms_to_ubo(nir_shader *shader, int multiplier);
 
 typedef struct nir_lower_subgroups_options {
diff --git a/src/compiler/nir/nir_lower_viewport_transform.c b/src/compiler/nir/nir_lower_viewport_transform.c
new file mode 100644
index 00000000000..66085b8da5a
--- /dev/null
+++ b/src/compiler/nir/nir_lower_viewport_transform.c
@@ -0,0 +1,101 @@ 
+/*
+ * Copyright (C) 2019 Alyssa Rosenzweig
+ *
+ * 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.
+ */
+
+/* On some hardware (particularly, all current versions of Mali GPUs),
+ * vertex shaders do not output gl_Position in world-space. Instead, they
+ * output gl_Position in transformed screen space via the "pseudo"
+ * position varying. Thus, this pass finds writes to gl_Position and
+ * changes them to transformed writes, still to gl_Position. The
+ * outputted screen space is still written back to VARYING_SLOT_POS,
+ * which is semantically ambiguous but nevertheless a good match for
+ * Gallium/NIR/Mali.
+ *
+ * Implements coordinate transformation as defined in section 12.5
+ * "Coordinate Transformation" of the OpenGL ES 3.2 full specification.
+ *
+ * This pass must run before lower_vars/lower_io such that derefs are
+ * still in place.
+ */
+
+#include "nir/nir.h"
+#include "nir/nir_builder.h"
+
+void
+nir_lower_viewport_transform(nir_shader *shader)
+{
+   assert(shader->info.stage == MESA_SHADER_VERTEX);
+
+   nir_foreach_function(func, shader) {
+      nir_foreach_block(block, func->impl) {
+         nir_foreach_instr_safe(instr, block) {
+            if (instr->type != nir_instr_type_intrinsic)
+               continue;
+
+            nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+            if (intr->intrinsic != nir_intrinsic_store_deref)
+               continue;
+
+            nir_variable *var = nir_intrinsic_get_var(intr, 0);
+            if (var->data.location != VARYING_SLOT_POS)
+               continue;
+
+            nir_builder b;
+            nir_builder_init(&b, func->impl);
+            b.cursor = nir_before_instr(instr);
+
+            /* Grab the source and viewport */
+            nir_ssa_def *input_point = nir_ssa_for_src(&b, intr->src[1], 4);
+            nir_ssa_def *scale = nir_load_viewport_scale(&b);
+            nir_ssa_def *offset = nir_load_viewport_offset(&b);
+
+            /* World space to normalised device coordinates to screen space */
+
+            nir_ssa_def *w_recip = nir_frcp(&b, nir_channel(&b, input_point, 3));
+
+            nir_ssa_def *ndc_point = nir_fmul(&b,
+                  nir_channels(&b, input_point, 0x7), w_recip);
+
+            nir_ssa_def *screen = nir_fadd(&b,
+                  nir_fmul(&b, ndc_point, scale), offset);
+
+            /* gl_Position will be written out in screenspace xyz, with w set to
+             * the reciprocal we computed earlier. The transformed w component is
+             * then used for perspective-correct varying interpolation. The
+             * transformed w component must preserve its original sign; this is
+             * used in depth clipping computations */
+
+            nir_ssa_def *screen_space = nir_vec4(&b,
+                             nir_channel(&b, screen, 0),
+                             nir_channel(&b, screen, 1),
+                             nir_channel(&b, screen, 2),
+                             w_recip);
+
+            nir_instr_rewrite_src(instr, &intr->src[1],
+                                  nir_src_for_ssa(screen_space));
+         }
+      }
+
+      nir_metadata_preserve(func->impl, nir_metadata_block_index |
+                            nir_metadata_dominance);
+   }
+}

Comments

This patch is

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

On 4/12/19 4:46 PM, Alyssa Rosenzweig wrote:
> On Mali hardware (supported by Panfrost and Lima), the fixed-function
> transformation from world-space to screen-space coordinates is done in
> the vertex shader prior to writing out the gl_Position varying, rather
> than in dedicated hardware. This commit adds a shared NIR pass for
> implementing coordinate transformation and lowering gl_Position writes
> into screen-space gl_Position writes.
> 
> v2: Run directly on derefs before io/vars are lowered to cleanup the
> code substantially. Thank you to Qiang for this suggestion!
> 
> v3: Bikeshed continues.
> 
> Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
> Suggested-by: Qiang Yu <yuq825@gmail.com>
> Cc: Jason Ekstrand <jason@jlekstrand.net>
> Cc: Eric Anholt <eric@anholt.net>
> ---
>  src/compiler/nir/meson.build                  |   1 +
>  src/compiler/nir/nir.h                        |   1 +
>  .../nir/nir_lower_viewport_transform.c        | 101 ++++++++++++++++++
>  3 files changed, 103 insertions(+)
>  create mode 100644 src/compiler/nir/nir_lower_viewport_transform.c
> 
> diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
> index c65f2ff62ff..c274361bdc4 100644
> --- a/src/compiler/nir/meson.build
> +++ b/src/compiler/nir/meson.build
> @@ -151,6 +151,7 @@ files_libnir = files(
>    'nir_lower_vars_to_ssa.c',
>    'nir_lower_var_copies.c',
>    'nir_lower_vec_to_movs.c',
> +  'nir_lower_viewport_transform.c',
>    'nir_lower_wpos_center.c',
>    'nir_lower_wpos_ytransform.c',
>    'nir_lower_bit_size.c',
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index bc72d8f83f5..0f6ed734efa 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -3124,6 +3124,7 @@ void nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask);
>  void nir_lower_io_to_scalar_early(nir_shader *shader, nir_variable_mode mask);
>  bool nir_lower_io_to_vector(nir_shader *shader, nir_variable_mode mask);
>  
> +void nir_lower_viewport_transform(nir_shader *shader);
>  bool nir_lower_uniforms_to_ubo(nir_shader *shader, int multiplier);
>  
>  typedef struct nir_lower_subgroups_options {
> diff --git a/src/compiler/nir/nir_lower_viewport_transform.c b/src/compiler/nir/nir_lower_viewport_transform.c
> new file mode 100644
> index 00000000000..66085b8da5a
> --- /dev/null
> +++ b/src/compiler/nir/nir_lower_viewport_transform.c
> @@ -0,0 +1,101 @@
> +/*
> + * Copyright (C) 2019 Alyssa Rosenzweig
> + *
> + * 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.
> + */
> +
> +/* On some hardware (particularly, all current versions of Mali GPUs),
> + * vertex shaders do not output gl_Position in world-space. Instead, they
> + * output gl_Position in transformed screen space via the "pseudo"
> + * position varying. Thus, this pass finds writes to gl_Position and
> + * changes them to transformed writes, still to gl_Position. The
> + * outputted screen space is still written back to VARYING_SLOT_POS,
> + * which is semantically ambiguous but nevertheless a good match for
> + * Gallium/NIR/Mali.
> + *
> + * Implements coordinate transformation as defined in section 12.5
> + * "Coordinate Transformation" of the OpenGL ES 3.2 full specification.
> + *
> + * This pass must run before lower_vars/lower_io such that derefs are
> + * still in place.
> + */
> +
> +#include "nir/nir.h"
> +#include "nir/nir_builder.h"
> +
> +void
> +nir_lower_viewport_transform(nir_shader *shader)
> +{
> +   assert(shader->info.stage == MESA_SHADER_VERTEX);
> +
> +   nir_foreach_function(func, shader) {
> +      nir_foreach_block(block, func->impl) {
> +         nir_foreach_instr_safe(instr, block) {
> +            if (instr->type != nir_instr_type_intrinsic)
> +               continue;
> +
> +            nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
> +            if (intr->intrinsic != nir_intrinsic_store_deref)
> +               continue;
> +
> +            nir_variable *var = nir_intrinsic_get_var(intr, 0);
> +            if (var->data.location != VARYING_SLOT_POS)
> +               continue;
> +
> +            nir_builder b;
> +            nir_builder_init(&b, func->impl);
> +            b.cursor = nir_before_instr(instr);
> +
> +            /* Grab the source and viewport */
> +            nir_ssa_def *input_point = nir_ssa_for_src(&b, intr->src[1], 4);
> +            nir_ssa_def *scale = nir_load_viewport_scale(&b);
> +            nir_ssa_def *offset = nir_load_viewport_offset(&b);
> +
> +            /* World space to normalised device coordinates to screen space */
> +
> +            nir_ssa_def *w_recip = nir_frcp(&b, nir_channel(&b, input_point, 3));
> +
> +            nir_ssa_def *ndc_point = nir_fmul(&b,
> +                  nir_channels(&b, input_point, 0x7), w_recip);
> +
> +            nir_ssa_def *screen = nir_fadd(&b,
> +                  nir_fmul(&b, ndc_point, scale), offset);
> +
> +            /* gl_Position will be written out in screenspace xyz, with w set to
> +             * the reciprocal we computed earlier. The transformed w component is
> +             * then used for perspective-correct varying interpolation. The
> +             * transformed w component must preserve its original sign; this is
> +             * used in depth clipping computations */
> +
> +            nir_ssa_def *screen_space = nir_vec4(&b,
> +                             nir_channel(&b, screen, 0),
> +                             nir_channel(&b, screen, 1),
> +                             nir_channel(&b, screen, 2),
> +                             w_recip);
> +
> +            nir_instr_rewrite_src(instr, &intr->src[1],
> +                                  nir_src_for_ssa(screen_space));
> +         }
> +      }
> +
> +      nir_metadata_preserve(func->impl, nir_metadata_block_index |
> +                            nir_metadata_dominance);
> +   }
> +}
>
Patch series are:
Reviewed-by: Qiang Yu <yuq825@gmail.com>

Regards,
Qiang


On Sat, Apr 13, 2019 at 7:46 AM Alyssa Rosenzweig <alyssa@rosenzweig.io> wrote:
>
> On Mali hardware (supported by Panfrost and Lima), the fixed-function
> transformation from world-space to screen-space coordinates is done in
> the vertex shader prior to writing out the gl_Position varying, rather
> than in dedicated hardware. This commit adds a shared NIR pass for
> implementing coordinate transformation and lowering gl_Position writes
> into screen-space gl_Position writes.
>
> v2: Run directly on derefs before io/vars are lowered to cleanup the
> code substantially. Thank you to Qiang for this suggestion!
>
> v3: Bikeshed continues.
>
> Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
> Suggested-by: Qiang Yu <yuq825@gmail.com>
> Cc: Jason Ekstrand <jason@jlekstrand.net>
> Cc: Eric Anholt <eric@anholt.net>
> ---
>  src/compiler/nir/meson.build                  |   1 +
>  src/compiler/nir/nir.h                        |   1 +
>  .../nir/nir_lower_viewport_transform.c        | 101 ++++++++++++++++++
>  3 files changed, 103 insertions(+)
>  create mode 100644 src/compiler/nir/nir_lower_viewport_transform.c
>
> diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
> index c65f2ff62ff..c274361bdc4 100644
> --- a/src/compiler/nir/meson.build
> +++ b/src/compiler/nir/meson.build
> @@ -151,6 +151,7 @@ files_libnir = files(
>    'nir_lower_vars_to_ssa.c',
>    'nir_lower_var_copies.c',
>    'nir_lower_vec_to_movs.c',
> +  'nir_lower_viewport_transform.c',
>    'nir_lower_wpos_center.c',
>    'nir_lower_wpos_ytransform.c',
>    'nir_lower_bit_size.c',
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index bc72d8f83f5..0f6ed734efa 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -3124,6 +3124,7 @@ void nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask);
>  void nir_lower_io_to_scalar_early(nir_shader *shader, nir_variable_mode mask);
>  bool nir_lower_io_to_vector(nir_shader *shader, nir_variable_mode mask);
>
> +void nir_lower_viewport_transform(nir_shader *shader);
>  bool nir_lower_uniforms_to_ubo(nir_shader *shader, int multiplier);
>
>  typedef struct nir_lower_subgroups_options {
> diff --git a/src/compiler/nir/nir_lower_viewport_transform.c b/src/compiler/nir/nir_lower_viewport_transform.c
> new file mode 100644
> index 00000000000..66085b8da5a
> --- /dev/null
> +++ b/src/compiler/nir/nir_lower_viewport_transform.c
> @@ -0,0 +1,101 @@
> +/*
> + * Copyright (C) 2019 Alyssa Rosenzweig
> + *
> + * 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.
> + */
> +
> +/* On some hardware (particularly, all current versions of Mali GPUs),
> + * vertex shaders do not output gl_Position in world-space. Instead, they
> + * output gl_Position in transformed screen space via the "pseudo"
> + * position varying. Thus, this pass finds writes to gl_Position and
> + * changes them to transformed writes, still to gl_Position. The
> + * outputted screen space is still written back to VARYING_SLOT_POS,
> + * which is semantically ambiguous but nevertheless a good match for
> + * Gallium/NIR/Mali.
> + *
> + * Implements coordinate transformation as defined in section 12.5
> + * "Coordinate Transformation" of the OpenGL ES 3.2 full specification.
> + *
> + * This pass must run before lower_vars/lower_io such that derefs are
> + * still in place.
> + */
> +
> +#include "nir/nir.h"
> +#include "nir/nir_builder.h"
> +
> +void
> +nir_lower_viewport_transform(nir_shader *shader)
> +{
> +   assert(shader->info.stage == MESA_SHADER_VERTEX);
> +
> +   nir_foreach_function(func, shader) {
> +      nir_foreach_block(block, func->impl) {
> +         nir_foreach_instr_safe(instr, block) {
> +            if (instr->type != nir_instr_type_intrinsic)
> +               continue;
> +
> +            nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
> +            if (intr->intrinsic != nir_intrinsic_store_deref)
> +               continue;
> +
> +            nir_variable *var = nir_intrinsic_get_var(intr, 0);
> +            if (var->data.location != VARYING_SLOT_POS)
> +               continue;
> +
> +            nir_builder b;
> +            nir_builder_init(&b, func->impl);
> +            b.cursor = nir_before_instr(instr);
> +
> +            /* Grab the source and viewport */
> +            nir_ssa_def *input_point = nir_ssa_for_src(&b, intr->src[1], 4);
> +            nir_ssa_def *scale = nir_load_viewport_scale(&b);
> +            nir_ssa_def *offset = nir_load_viewport_offset(&b);
> +
> +            /* World space to normalised device coordinates to screen space */
> +
> +            nir_ssa_def *w_recip = nir_frcp(&b, nir_channel(&b, input_point, 3));
> +
> +            nir_ssa_def *ndc_point = nir_fmul(&b,
> +                  nir_channels(&b, input_point, 0x7), w_recip);
> +
> +            nir_ssa_def *screen = nir_fadd(&b,
> +                  nir_fmul(&b, ndc_point, scale), offset);
> +
> +            /* gl_Position will be written out in screenspace xyz, with w set to
> +             * the reciprocal we computed earlier. The transformed w component is
> +             * then used for perspective-correct varying interpolation. The
> +             * transformed w component must preserve its original sign; this is
> +             * used in depth clipping computations */
> +
> +            nir_ssa_def *screen_space = nir_vec4(&b,
> +                             nir_channel(&b, screen, 0),
> +                             nir_channel(&b, screen, 1),
> +                             nir_channel(&b, screen, 2),
> +                             w_recip);
> +
> +            nir_instr_rewrite_src(instr, &intr->src[1],
> +                                  nir_src_for_ssa(screen_space));
> +         }
> +      }
> +
> +      nir_metadata_preserve(func->impl, nir_metadata_block_index |
> +                            nir_metadata_dominance);
> +   }
> +}
> --
> 2.20.1
>