Mesa (master): i965/vs: Sample from MCS surface when required

[Chris Forbes]

Module: Mesa
Branch: master
Commit: 3122c2421a46207e06481ade5ccd5c864d13091a
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=3122c2421a46207e06481ade5ccd5c864d13091a

Author: Chris Forbes <chrisf at ijw.co.nz>
Date:   Sat Nov 30 13:49:50 2013 +1300

i965/vs: Sample from MCS surface when required

Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
Reviewed-by: Paul Berry <stereotype441 at gmail.com>

---

 src/mesa/drivers/dri/i965/brw_vec4.h           |    1 +
 src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp |   46 ++++++++++++++++++++----
 2 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_vec4.h b/src/mesa/drivers/dri/i965/brw_vec4.h
index 5cec9f9..d4029d8 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.h
+++ b/src/mesa/drivers/dri/i965/brw_vec4.h
@@ -477,6 +477,7 @@ public:
    void emit_unpack_half_2x16(dst_reg dst, src_reg src0);
 
    uint32_t gather_channel(ir_texture *ir, int sampler);
+   src_reg emit_mcs_fetch(ir_texture *ir, src_reg coordinate, int sampler);
    void swizzle_result(ir_texture *ir, src_reg orig_val, int sampler);
 
    void emit_ndc_computation();
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index 6c5b5c6..b599c29 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -2242,6 +2242,31 @@ vec4_visitor::visit(ir_call *ir)
    }
 }
 
+src_reg
+vec4_visitor::emit_mcs_fetch(ir_texture *ir, src_reg coordinate, int sampler)
+{
+   vec4_instruction *inst = new(mem_ctx) vec4_instruction(this, SHADER_OPCODE_TXF_MCS);
+   inst->base_mrf = 2;
+   inst->mlen = 1;
+   inst->sampler = sampler;
+   inst->dst = dst_reg(this, glsl_type::uvec4_type);
+   inst->dst.writemask = WRITEMASK_XYZW;
+
+   /* parameters are: u, v, r, lod; lod will always be zero due to api restrictions */
+   int param_base = inst->base_mrf;
+   int coord_mask = (1 << ir->coordinate->type->vector_elements) - 1;
+   int zero_mask = 0xf & ~coord_mask;
+
+   emit(MOV(dst_reg(MRF, param_base, ir->coordinate->type, coord_mask),
+            coordinate));
+
+   emit(MOV(dst_reg(MRF, param_base, ir->coordinate->type, zero_mask),
+            src_reg(0)));
+
+   emit(inst);
+   return src_reg(inst->dst);
+}
+
 void
 vec4_visitor::visit(ir_texture *ir)
 {
@@ -2292,7 +2317,7 @@ vec4_visitor::visit(ir_texture *ir)
    }
 
    const glsl_type *lod_type = NULL, *sample_index_type = NULL;
-   src_reg lod, dPdx, dPdy, sample_index;
+   src_reg lod, dPdx, dPdy, sample_index, mcs;
    switch (ir->op) {
    case ir_tex:
       lod = src_reg(0.0f);
@@ -2313,6 +2338,11 @@ vec4_visitor::visit(ir_texture *ir)
       ir->lod_info.sample_index->accept(this);
       sample_index = this->result;
       sample_index_type = ir->lod_info.sample_index->type;
+
+      if (brw->gen >= 7 && key->tex.compressed_multisample_layout_mask & (1<<sampler))
+         mcs = emit_mcs_fetch(ir, coordinate, sampler);
+      else
+         mcs = src_reg(0u);
       break;
    case ir_txd:
       ir->lod_info.grad.dPdx->accept(this);
@@ -2433,13 +2463,15 @@ vec4_visitor::visit(ir_texture *ir)
       } else if (ir->op == ir_txf_ms) {
          emit(MOV(dst_reg(MRF, param_base + 1, sample_index_type, WRITEMASK_X),
                   sample_index));
+         if (brw->gen >= 7)
+            /* MCS data is in the first channel of `mcs`, but we need to get it into
+             * the .y channel of the second vec4 of params, so replicate .x across
+             * the whole vec4 and then mask off everything except .y
+             */
+            mcs.swizzle = BRW_SWIZZLE_XXXX;
+            emit(MOV(dst_reg(MRF, param_base + 1, glsl_type::uint_type, WRITEMASK_Y),
+                     mcs));
          inst->mlen++;
-
-         /* on Gen7, there is an additional MCS parameter here after SI,
-          * but we don't bother to emit it since it's always zero. If
-          * we start supporting texturing from CMS surfaces, this will have
-          * to change
-          */
       } else if (ir->op == ir_txd) {
 	 const glsl_type *type = lod_type;