Mesa (master): nir/lower_tex: Add support for lowering texture swizzle

[Jason Ekstrand]

Module: Mesa
Branch: master
Commit: 8537b4ab762ec4249acf23164e0e5a943d2d05af
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=8537b4ab762ec4249acf23164e0e5a943d2d05af

Author: Jason Ekstrand <jason.ekstrand at intel.com>
Date:   Wed Nov 11 18:30:31 2015 -0800

nir/lower_tex: Add support for lowering texture swizzle

Reviewed-by: Connor Abbott <cwabbott0 at gmail.com>

---

 src/glsl/nir/nir.h           |   13 ++++++++
 src/glsl/nir/nir_lower_tex.c |   67 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+)

diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 1baef19..524717a 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -2019,6 +2019,19 @@ typedef struct nir_lower_tex_options {
    unsigned saturate_s;
    unsigned saturate_t;
    unsigned saturate_r;
+
+   /* Bitmask of samplers that need swizzling.
+    *
+    * If (swizzle_result & (1 << sampler_index)), then the swizzle in
+    * swizzles[sampler_index] is applied to the result of the texturing
+    * operation.
+    */
+   unsigned swizzle_result;
+
+   /* A swizzle for each sampler.  Values 0-3 represent x, y, z, or w swizzles
+    * while 4 and 5 represent 0 and 1 respectively.
+    */
+   uint8_t swizzles[32][4];
 } nir_lower_tex_options;
 
 bool nir_lower_tex(nir_shader *shader,
diff --git a/src/glsl/nir/nir_lower_tex.c b/src/glsl/nir/nir_lower_tex.c
index 6dea837..93ebf8e 100644
--- a/src/glsl/nir/nir_lower_tex.c
+++ b/src/glsl/nir/nir_lower_tex.c
@@ -215,6 +215,66 @@ saturate_src(nir_builder *b, nir_tex_instr *tex, unsigned sat_mask)
    }
 }
 
+static nir_ssa_def *
+get_zero_or_one(nir_builder *b, nir_alu_type type, uint8_t swizzle_val)
+{
+   nir_const_value v;
+
+   memset(&v, 0, sizeof(v));
+
+   if (swizzle_val == 4) {
+      v.u[0] = v.u[1] = v.u[2] = v.u[3] = 0;
+   } else {
+      assert(swizzle_val == 5);
+      if (type == nir_type_float)
+         v.f[0] = v.f[1] = v.f[2] = v.f[3] = 1.0;
+      else
+         v.u[0] = v.u[1] = v.u[2] = v.u[3] = 1;
+   }
+
+   return nir_build_imm(b, 4, v);
+}
+
+static void
+swizzle_result(nir_builder *b, nir_tex_instr *tex, const uint8_t swizzle[4])
+{
+   assert(tex->dest.is_ssa);
+
+   b->cursor = nir_after_instr(&tex->instr);
+
+   nir_ssa_def *swizzled;
+   if (tex->op == nir_texop_tg4) {
+      if (swizzle[tex->component] < 4) {
+         /* This one's easy */
+         tex->component = swizzle[tex->component];
+         return;
+      } else {
+         swizzled = get_zero_or_one(b, tex->dest_type, swizzle[tex->component]);
+      }
+   } else {
+      assert(nir_tex_instr_dest_size(tex) == 4);
+      if (swizzle[0] < 4 && swizzle[1] < 4 &&
+          swizzle[2] < 4 && swizzle[3] < 4) {
+         unsigned swiz[4] = { swizzle[0], swizzle[1], swizzle[2], swizzle[3] };
+         /* We have no 0's or 1's, just emit a swizzling MOV */
+         swizzled = nir_swizzle(b, &tex->dest.ssa, swiz, 4, false);
+      } else {
+         nir_ssa_def *srcs[4];
+         for (unsigned i = 0; i < 4; i++) {
+            if (swizzle[i] < 4) {
+               srcs[i] = nir_channel(b, &tex->dest.ssa, swizzle[i]);
+            } else {
+               srcs[i] = get_zero_or_one(b, tex->dest_type, swizzle[i]);
+            }
+         }
+         swizzled = nir_vec(b, srcs, 4);
+      }
+   }
+
+   nir_ssa_def_rewrite_uses_after(&tex->dest.ssa, nir_src_for_ssa(swizzled),
+                                  swizzled->parent_instr);
+}
+
 static bool
 nir_lower_tex_block(nir_block *block, void *void_state)
 {
@@ -256,6 +316,13 @@ nir_lower_tex_block(nir_block *block, void *void_state)
          saturate_src(b, tex, sat_mask);
          state->progress = true;
       }
+
+      if (((1 << tex->sampler_index) & state->options->swizzle_result) &&
+          !nir_tex_instr_is_query(tex) &&
+          !(tex->is_shadow && tex->is_new_style_shadow)) {
+         swizzle_result(b, tex, state->options->swizzles[tex->sampler_index]);
+         state->progress = true;
+      }
    }
 
    return true;