[Mesa-dev] [PATCH 2/2] svga: implement MSAA alpha_to_one feature

[Charmaine Lee]

>From: Brian Paul <brianp at vmware.com>
>Sent: Saturday, July 22, 2017 12:24 PM
>To: mesa-dev at lists.freedesktop.org
>Cc: Charmaine Lee; Neha Bhende
>Subject: [PATCH 2/2] svga: implement MSAA alpha_to_one feature

>The device doesn't directly support this feature so we implement it with
>additional shader code which sets the color output(s) w component to
>1.0 (or max_int or max_uint).

>Fixes 16 Piglit ext_framebuffer_multisample/*alpha-to-one* tests.
>---
> src/gallium/drivers/svga/svga_context.h     |  1 +
> src/gallium/drivers/svga/svga_pipe_blend.c  |  1 +
> src/gallium/drivers/svga/svga_shader.h      |  3 ++
> src/gallium/drivers/svga/svga_state_fs.c    | 18 +++++++++
> src/gallium/drivers/svga/svga_tgsi_vgpu10.c | 61 ++++++++++++++++++++++++++++-
> 5 files changed, 83 insertions(+), 1 deletion(-)

...


>diff --git a/src/gallium/drivers/svga/svga_tgsi_vgpu10.c b/src/gallium/drivers/svga/svga_tgsi_vgpu10.c
>index 9f5cd4b..8984ce5 100644
>--- a/src/gallium/drivers/svga/svga_tgsi_vgpu10.c
>+++ b/src/gallium/drivers/svga/svga_tgsi_vgpu10.c

...

@@ -6378,6 +6393,47 @@ emit_pre_helpers(struct svga_shader_emitter_v10 *emit)


> /**
>+ * The device has no direct support for the pipe_blend_state::alpha_to_one
>+ * option so we implement it here with shader code.
>+ */
>+static void
>+emit_alpha_to_one_instructions(struct svga_shader_emitter_v10 *emit,
>+                               unsigned fs_color_tmp_index)
>+{
>+   unsigned i;
>+
>+   for (i = 0; i < emit->fs.num_color_outputs; i++) {
>+      struct tgsi_full_dst_register color_dst;
>+
>+      if (fs_color_tmp_index != INVALID_INDEX && i == 0) {
>+         /* write to the temp color register */
>+         color_dst = make_dst_temp_reg(fs_color_tmp_index);
>+      }
>+      else {
>+         /* write directly to the color[i] output */
>+         color_dst = make_dst_output_reg(emit->fs.color_out_index[i]);
>+      }
>+
>+      color_dst = writemask_dst(&color_dst, TGSI_WRITEMASK_W);
>+
>+      /* Depending on type of the render target, we either set alpha/w to
>+       * 1.0f, or max(int) or max(uint).
>+       */
>+      struct tgsi_full_src_register one;
>+      if (emit->key.fs.int_render_target_mask & (1 << i)) {
>+         one = make_immediate_reg_int(emit, 0x8fffffff);
>+      } else if (emit->key.fs.uint_render_target_mask & (1 << i)) {
>+         one = make_immediate_reg_int(emit, 0xffffffff);
>+      } else {
>+         one = make_immediate_reg_float(emit, 1.0f);
>+      }

How about moving the various "make one immediate" outside of the loop?
No need to repeatedly looking for the same immediate.  

-Charmaine