Mesa (master): i965: Fix variable indexing of sampler arrays under non-uniform control flow.

[Francisco Jerez]

Module: Mesa
Branch: master
Commit: e1ae0c3bc37be7b1de21ee248d674671d01da8e6
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=e1ae0c3bc37be7b1de21ee248d674671d01da8e6

Author: Francisco Jerez <currojerez at riseup.net>
Date:   Thu Feb 19 14:49:10 2015 +0200

i965: Fix variable indexing of sampler arrays under non-uniform control flow.

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

Reviewed-by: Matt Turner <mattst88 at gmail.com>

---

 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 4c968f0..555987d 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -1707,8 +1707,8 @@ 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 2128795..c080e9b 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -2317,8 +2317,9 @@ 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 f0416be..203ac46 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp
@@ -2518,8 +2518,9 @@ 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