i965/fs: Add infrastructure for generating CSEL instructions.

v2 (idr): Don't allow CSEL with a non-float src2.

v3 (idr): Add CSEL to fs_inst::flags_written.  Suggested by Matt.

v4 (idr): Only set BRW_ALIGN_16 on Gen < 10 (suggested by Matt).  Don't
reset the access mode afterwards (suggested by Samuel and Matt).  Add
support for CSEL not modifying the flags to more places (requested by
Matt).

Signed-off-by: Kenneth Graunke <[email protected]>
Signed-off-by: Ian Romanick <[email protected]>
Reviewed-by: Samuel Iglesias Gonsálvez <[email protected]> [v3]
Reviewed-by: Matt Turner <[email protected]>

1 files changed, 21 insertions, 1 deletions

diff --git a/src/intel/compiler/brw_fs_builder.h b/src/intel/compiler/brw_fs_builder.h
index cf603b0c868..4203c8c27c3 100644
--- a/src/intel/compiler/brw_fs_builder.h
+++ b/src/intel/compiler/brw_fs_builder.h
@@ -567,7 +567,6 @@ namespace brw {
       ALU1(BFREV)
       ALU1(CBIT)
       ALU2(CMPN)
-      ALU3(CSEL)
       ALU1(DIM)
       ALU2(DP2)
       ALU2(DP3)
@@ -643,6 +642,27 @@ namespace brw {
       }
 
       /**
+       * CSEL: dst = src2 <op> 0.0f ? src0 : src1
+       */
+      instruction *
+      CSEL(const dst_reg &dst, const src_reg &src0, const src_reg &src1,
+           const src_reg &src2, brw_conditional_mod condition) const
+      {
+         /* CSEL only operates on floats, so we can't do integer </<=/>=/>
+          * comparisons.  Zero/non-zero (== and !=) comparisons almost work.
+          * 0x80000000 fails because it is -0.0, and -0.0 == 0.0.
+          */
+         assert(src2.type == BRW_REGISTER_TYPE_F);
+
+         return set_condmod(condition,
+                            emit(BRW_OPCODE_CSEL,
+                                 retype(dst, BRW_REGISTER_TYPE_F),
+                                 retype(src0, BRW_REGISTER_TYPE_F),
+                                 retype(src1, BRW_REGISTER_TYPE_F),
+                                 src2));
+      }
+
+      /**
        * Emit a linear interpolation instruction.
        */
       instruction *