i965: Enable EXT_shader_samples_identical

On the vec4 backend, textureSamplesIdentical() will always return
false.  There are currently no test cases for the vec4 backend, so we
don't have much confidence in any implementation.  We also don't think
anyone is likely to miss it.

v2: Handle immediate value for MCS smarter.  Rebase on changes to
nir_texop_sampels_identical (missing second parameter).  Suggested by
Jason.

v3: Add Neil's code to handle 16x MSAA in the FS.  Also rebase on top of
f9a9ba5e.  Stub out the vec4 implementation.

Signed-off-by: Ian Romanick <[email protected]>
Signed-off-by: Neil Roberts <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]> [v2]
Reviewed-by: Chris Forbes <[email protected]> [v2]

5 files changed, 34 insertions, 2 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index 8fc7ee42d6b..b6e5ed6a72b 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -2625,6 +2625,7 @@ fs_visitor::nir_emit_texture(const fs_builder &bld, nir_tex_instr *instr)
          switch (instr->op) {
          case nir_texop_txf:
          case nir_texop_txf_ms:
+         case nir_texop_samples_identical:
             coordinate = retype(src, BRW_REGISTER_TYPE_D);
             break;
          default:
@@ -2687,7 +2688,8 @@ fs_visitor::nir_emit_texture(const fs_builder &bld, nir_tex_instr *instr)
       }
    }
 
-   if (instr->op == nir_texop_txf_ms) {
+   if (instr->op == nir_texop_txf_ms ||
+       instr->op == nir_texop_samples_identical) {
       if (devinfo->gen >= 7 &&
           key_tex->compressed_multisample_layout_mask & (1 << sampler)) {
          mcs = emit_mcs_fetch(coordinate, instr->coord_components, sampler_reg);
diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index d97fcf33b62..2e04134318e 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -259,6 +259,26 @@ fs_visitor::emit_texture(ir_texture_opcode op,
       lod = brw_imm_ud(0u);
    }
 
+   if (op == ir_samples_identical) {
+      fs_reg dst = vgrf(glsl_type::get_instance(dest_type->base_type, 1, 1));
+
+      /* If mcs is an immediate value, it means there is no MCS.  In that case
+       * just return false.
+       */
+      if (mcs.file == BRW_IMMEDIATE_VALUE) {
+         bld.MOV(dst, brw_imm_ud(0u));
+      } else if ((key_tex->msaa_16 & (1 << sampler))) {
+         fs_reg tmp = vgrf(glsl_type::uint_type);
+         bld.OR(tmp, mcs, offset(mcs, bld, 1));
+         bld.CMP(dst, tmp, brw_imm_ud(0u), BRW_CONDITIONAL_EQ);
+      } else {
+         bld.CMP(dst, mcs, brw_imm_ud(0u), BRW_CONDITIONAL_EQ);
+      }
+
+      this->result = dst;
+      return;
+   }
+
    if (coordinate.file != BAD_FILE) {
       /* FINISHME: Texture coordinate rescaling doesn't work with non-constant
        * samplers.  This should only be a problem with GL_CLAMP on Gen7.
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
index 63696a7ad5b..28656d45b33 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_nir.cpp
@@ -1615,6 +1615,7 @@ vec4_visitor::nir_emit_texture(nir_tex_instr *instr)
          switch (instr->op) {
          case nir_texop_txf:
          case nir_texop_txf_ms:
+         case nir_texop_samples_identical:
             coordinate = get_nir_src(instr->src[i].src, BRW_REGISTER_TYPE_D,
                                      src_size);
             coord_type = glsl_type::ivec(src_size);
@@ -1695,7 +1696,8 @@ vec4_visitor::nir_emit_texture(nir_tex_instr *instr)
       }
    }
 
-   if (instr->op == nir_texop_txf_ms) {
+   if (instr->op == nir_texop_txf_ms ||
+       instr->op == nir_texop_samples_identical) {
       assert(coord_type != NULL);
       if (devinfo->gen >= 7 &&
           key_tex->compressed_multisample_layout_mask & (1 << sampler)) {
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index 08a1f8bb77c..2e4695a2845 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -909,6 +909,13 @@ vec4_visitor::emit_texture(ir_texture_opcode op,
       unreachable("TXB is not valid for vertex shaders.");
    case ir_lod:
       unreachable("LOD is not valid for vertex shaders.");
+   case ir_samples_identical: {
+      /* There are some challenges implementing this for vec4, and it seems
+       * unlikely to be used anyway.  For now, just return false ways.
+       */
+      emit(MOV(dest, brw_imm_ud(0u)));
+      return;
+   }
    default:
       unreachable("Unrecognized tex op");
    }
diff --git a/src/mesa/drivers/dri/i965/intel_extensions.c b/src/mesa/drivers/dri/i965/intel_extensions.c
index 386b63c123d..2e2459c125b 100644
--- a/src/mesa/drivers/dri/i965/intel_extensions.c
+++ b/src/mesa/drivers/dri/i965/intel_extensions.c
@@ -333,6 +333,7 @@ intelInitExtensions(struct gl_context *ctx)
       ctx->Extensions.ARB_texture_compression_bptc = true;
       ctx->Extensions.ARB_texture_view = true;
       ctx->Extensions.ARB_shader_storage_buffer_object = true;
+      ctx->Extensions.EXT_shader_samples_identical = true;
 
       if (can_do_pipelined_register_writes(brw)) {
          ctx->Extensions.ARB_draw_indirect = true;