<div class="gmail_quote">On 21 May 2012 18:00, Ian Romanick <<a href="mailto:idr@freedesktop.org" target="_blank">idr@freedesktop.org</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div class="HOEnZb"><div class="h5">On 05/11/2012 11:03 AM, Paul Berry wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> This patch modifies the function brw_blorp_blit_program::texel_fetch() to emit the SI (sample index) argument to the SAMPLE_LD message when reading from a sample index other than zero. Previously we were using the ugly hack of configuring multisampled source surfaces as single-sampled, and accessing sample indices other than zero by swizzling the texture coordinates in the WM program. --- src/mesa/drivers/dri/i965/brw_blorp.cpp | 7 +--- src/mesa/drivers/dri/i965/brw_blorp_blit.cpp | 45 ++++++++++++++++--------- 2 files changed, 31 insertions(+), 21 deletions(-) diff --git a/src/mesa/drivers/dri/i965/brw_blorp.cpp b/src/mesa/drivers/dri/i965/brw_blorp.cpp index 8e22511..f6aff44 100644 --- a/src/mesa/drivers/dri/i965/brw_blorp.cpp +++ b/src/mesa/drivers/dri/i965/brw_blorp.cpp @@ -57,19 +57,16 @@ brw_blorp_surface_info::set(struct intel_mipmap_tree *mt, unsigned int level, unsigned int layer) { brw_blorp_mip_info::set(mt, level, layer); + this->num_samples = mt->num_samples; if (mt->format == MESA_FORMAT_S8) { /* The miptree is a W-tiled stencil buffer. Surface states can't be set * up for W tiling, so we'll need to use Y tiling and have the WM - * program swizzle the coordinates. Furthermore, we need to set up the - * surface state as single-sampled, because the memory layout of related - * samples doesn't match between W and Y tiling. + * program swizzle the coordinates. */ this->map_stencil_as_y_tiled = true; - this->num_samples = 0; } else { this->map_stencil_as_y_tiled = false; - this->num_samples = mt->num_samples; } } diff --git a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp index d3ab0ba..e985fad 100644 --- a/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp +++ b/src/mesa/drivers/dri/i965/brw_blorp_blit.cpp @@ -220,6 +220,8 @@ enum sampler_message_arg SAMPLER_MESSAGE_ARG_V_FLOAT, SAMPLER_MESSAGE_ARG_U_INT, SAMPLER_MESSAGE_ARG_V_INT, + SAMPLER_MESSAGE_ARG_SI_INT, + SAMPLER_MESSAGE_ARG_ZERO_INT, }; /** @@ -435,14 +437,6 @@ brw_blorp_blit_program::compile(struct brw_context *brw, GLuint *program_size) { /* Sanity checks */ - if (key->src_tiled_w) { - /* If the source image is W tiled, then tex_samples must be 0. - * Otherwise, after conversion between W and Y tiling, there's no - * guarantee that the sample index will be 0. - */ - assert(key->tex_samples == 0); - } - if (key->dst_tiled_w) { /* If the destination image is W tiled, then dst_samples must be 0. * Otherwise, after conversion between W and Y tiling, there's no @@ -920,13 +914,15 @@ brw_blorp_blit_program::sample() void brw_blorp_blit_program::texel_fetch() { - static const sampler_message_arg args[2] = { + static const sampler_message_arg args[5] = { SAMPLER_MESSAGE_ARG_U_INT, - SAMPLER_MESSAGE_ARG_V_INT + SAMPLER_MESSAGE_ARG_V_INT, + SAMPLER_MESSAGE_ARG_ZERO_INT, /* R */ + SAMPLER_MESSAGE_ARG_ZERO_INT, /* LOD */ + SAMPLER_MESSAGE_ARG_SI_INT }; - assert(s_is_zero); - texture_lookup(GEN5_SAMPLER_MESSAGE_SAMPLE_LD, args, ARRAY_SIZE(args)); + texture_lookup(GEN5_SAMPLER_MESSAGE_SAMPLE_LD, args, s_is_zero ? 2 : 5); } void @@ -960,6 +956,15 @@ brw_blorp_blit_program::texture_lookup(GLuint msg_type, case SAMPLER_MESSAGE_ARG_V_INT: expand_to_32_bits(Y, mrf); break; + case SAMPLER_MESSAGE_ARG_SI_INT: + if (s_is_zero) + brw_MOV(&func, mrf, brw_imm_ud(0)); + else + expand_to_32_bits(S, mrf); + break; </blockquote> </div></div> It seems like up above you've guaranteed that you won't see SAMPLER_MESSAGE_ARG_SI_INT when s_is_zero. Is this extra check necessary? </blockquote><div> </div><div>You're certainly right for Gen6. On Gen7 it's necessary, though, because on Gen7, when downsampling, the fragment shader has to grab all N samples (using N texel fetches) and blend them manually. When it's grabbing sample 0, we will see SAMPLER_MESSAGE_ARG_SI_INT with s_is_zero=true.</div> <div> </div><div>I'll add a comment above the "if (s_is_zero)" line to explain why it's necessary.</div></div>