Mesa (master): i965/fs: Pass a BAD_FILE register to the logical FB write when oMask is unused.

[Francisco Jerez]

Module: Mesa
Branch: master
Commit: b0c8e5e0c88f7c5d7395715e58a8731e2ab55f7e
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=b0c8e5e0c88f7c5d7395715e58a8731e2ab55f7e

Author: Francisco Jerez <currojerez at riseup.net>
Date:   Fri Apr 29 19:47:44 2016 -0700

i965/fs: Pass a BAD_FILE register to the logical FB write when oMask is unused.

This will let the optimizer know that the sample mask value is unused
so its definition can be DCE'ed.

Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

---

 src/mesa/drivers/dri/i965/brw_fs.cpp         | 2 +-
 src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index f5add6e..0b350d5 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -3797,7 +3797,7 @@ lower_fb_write_logical_send(const fs_builder &bld, fs_inst *inst,
       length++;
    }
 
-   if (prog_data->uses_omask) {
+   if (sample_mask.file != BAD_FILE) {
       sources[length] = fs_reg(VGRF, bld.shader->alloc.allocate(1),
                                BRW_REGISTER_TYPE_UD);
 
diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index 25e1a44..3a49794 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -394,7 +394,8 @@ fs_visitor::emit_single_fb_write(const fs_builder &bld,
 
    const fs_reg sources[] = {
       color0, color1, src0_alpha, src_depth, dst_depth, src_stencil,
-      sample_mask, brw_imm_ud(components)
+      (prog_data->uses_omask ? sample_mask : fs_reg()),
+      brw_imm_ud(components)
    };
    assert(ARRAY_SIZE(sources) - 1 == FB_WRITE_LOGICAL_SRC_COMPONENTS);
    fs_inst *write = bld.emit(FS_OPCODE_FB_WRITE_LOGICAL, fs_reg(),