intel/fs: Simplify fs_visitor::emit_samplepos_setup

The original code manually handled splitting the MOVs to 8-wide to
handle various regioning restrictions.  Now that we have a SIMD width
splitting pass that handles these things, we can just emit everything at
the full width and let the SIMD splitting pass handle it.  We also now
have a useful "subscript" helper which is designed exactly for the case
where you want to take a W type and read it as a vector of Bs so we may
as well use that too.

Reviewed-by: Jason Ekstrand <[email protected]>
Reviewed-by: Matt Turner <[email protected]>

1 files changed, 7 insertions, 21 deletions

diff --git a/src/intel/compiler/brw_fs.cpp b/src/intel/compiler/brw_fs.cpp
index 73617e25804..893a7e2e526 100644
--- a/src/intel/compiler/brw_fs.cpp
+++ b/src/intel/compiler/brw_fs.cpp
@@ -1213,30 +1213,16 @@ fs_visitor::emit_samplepos_setup()
     * The X, Y sample positions come in as bytes in  thread payload. So, read
     * the positions using vstride=16, width=8, hstride=2.
     */
-   struct brw_reg sample_pos_reg =
-      stride(retype(brw_vec1_grf(payload.sample_pos_reg, 0),
-                    BRW_REGISTER_TYPE_B), 16, 8, 2);
+   const fs_reg sample_pos_reg = retype(brw_vec8_grf(payload.sample_pos_reg, 0),
+                                        BRW_REGISTER_TYPE_W);
 
-   if (dispatch_width == 8) {
-      abld.MOV(int_sample_x, fs_reg(sample_pos_reg));
-   } else {
-      abld.half(0).MOV(half(int_sample_x, 0), fs_reg(sample_pos_reg));
-      abld.half(1).MOV(half(int_sample_x, 1),
-                       fs_reg(suboffset(sample_pos_reg, 16)));
-   }
    /* Compute gl_SamplePosition.x */
-   compute_sample_position(pos, int_sample_x);
-   pos = offset(pos, abld, 1);
-   if (dispatch_width == 8) {
-      abld.MOV(int_sample_y, fs_reg(suboffset(sample_pos_reg, 1)));
-   } else {
-      abld.half(0).MOV(half(int_sample_y, 0),
-                       fs_reg(suboffset(sample_pos_reg, 1)));
-      abld.half(1).MOV(half(int_sample_y, 1),
-                       fs_reg(suboffset(sample_pos_reg, 17)));
-   }
+   abld.MOV(int_sample_x, subscript(sample_pos_reg, BRW_REGISTER_TYPE_B, 0));
+   compute_sample_position(offset(pos, abld, 0), int_sample_x);
+
    /* Compute gl_SamplePosition.y */
-   compute_sample_position(pos, int_sample_y);
+   abld.MOV(int_sample_y, subscript(sample_pos_reg, BRW_REGISTER_TYPE_B, 1));
+   compute_sample_position(offset(pos, abld, 1), int_sample_y);
    return reg;
 }