[Mesa-dev] [PATCH 7/7] i965: Fix variable indexing of sampler arrays under non-uniform control flow.

[Francisco Jerez]

ARB_gpu_shader5 requires sampler array indexing expressions to be
dynamically uniform, this however doesn't have any implications on the
control flow that leads to the evaluation of that expression being
uniform.  Use emit_uniformize() to obtain an arbitrary live value from
the binding table index calculation instead of assuming that the first
channel is always live.

Fixes the following Piglit test cases:
  arb_gpu_shader5/execution/sampler_array_indexing/fs-nonuniform-control-flow.shader_test
  arb_gpu_shader5/execution/sampler_array_indexing/vs-nonuniform-control-flow.shader_test

part of the series:
  http://lists.freedesktop.org/archives/piglit/2015-February/014615.html
---
 src/mesa/drivers/dri/i965/brw_fs_nir.cpp       | 4 ++--
 src/mesa/drivers/dri/i965/brw_fs_visitor.cpp   | 5 +++--
 src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp | 5 +++--
 3 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index ad77752..030ce24 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -1563,8 +1563,8 @@ fs_visitor::nir_emit_texture(nir_tex_instr *instr)
 
          /* Emit code to evaluate the actual indexing expression */
          sampler_reg = vgrf(glsl_type::uint_type);
-         emit(ADD(sampler_reg, src, fs_reg(sampler)))
-             ->force_writemask_all = true;
+         emit(ADD(sampler_reg, src, fs_reg(sampler)));
+         emit_uniformize(sampler_reg, sampler_reg);
          break;
       }
 
diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index dee6a6d..d7cad9f 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -2166,8 +2166,9 @@ fs_visitor::visit(ir_texture *ir)
       /* Emit code to evaluate the actual indexing expression */
       nonconst_sampler_index->accept(this);
       fs_reg temp = vgrf(glsl_type::uint_type);
-      emit(ADD(temp, this->result, fs_reg(sampler)))
-            ->force_writemask_all = true;
+      emit(ADD(temp, this->result, fs_reg(sampler)));
+      emit_uniformize(temp, temp);
+
       sampler_reg = temp;
    } else {
       /* Single sampler, or constant array index; the indexing expression
diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
index d5848d2..c260381 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -2497,8 +2497,9 @@ vec4_visitor::visit(ir_texture *ir)
       /* Emit code to evaluate the actual indexing expression */
       nonconst_sampler_index->accept(this);
       dst_reg temp(this, glsl_type::uint_type);
-      emit(ADD(temp, this->result, src_reg(sampler)))
-         ->force_writemask_all = true;
+      emit(ADD(temp, this->result, src_reg(sampler)));
+      emit_uniformize(temp, src_reg(temp));
+
       sampler_reg = src_reg(temp);
    } else {
       /* Single sampler, or constant array index; the indexing expression
-- 
2.1.3