[Mesa-dev] [PATCH] i965/fs: Replace nested ternary with if ladder.

[Matt Turner]

Since the types of the expression were

   bool ? src_reg : (bool ? brw_reg : brw_reg)

the result of the second (nested) ternary would be implicitly
converted to a src_reg by the src_reg(struct brw_reg) constructor. I.e.,

   bool ? src_reg : src_reg(bool ? brw_reg : brw_reg)

In the next patch, I make backend_reg (the parent of src_reg) inherit
from brw_reg, which changes this expression to return brw_reg, which
throws away any fields that exist in the classes derived from brw_reg.
I.e.,

   src_reg(bool ? brw_reg(src_reg) : bool ? brw_reg : brw_reg)

Generally this code was gross, and wasn't actually shorter or easier to
read than an if ladder.
---
 src/mesa/drivers/dri/i965/brw_fs_builder.h | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_builder.h b/src/mesa/drivers/dri/i965/brw_fs_builder.h
index f121f34..d5763f6 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_builder.h
+++ b/src/mesa/drivers/dri/i965/brw_fs_builder.h
@@ -224,12 +224,13 @@ namespace brw {
       src_reg
       sample_mask_reg() const
       {
-         const bool uses_kill =
-            (shader->stage == MESA_SHADER_FRAGMENT &&
-             ((brw_wm_prog_data *)shader->stage_prog_data)->uses_kill);
-         return (shader->stage != MESA_SHADER_FRAGMENT ? src_reg(0xffff) :
-                 uses_kill ? brw_flag_reg(0, 1) :
-                 retype(brw_vec1_grf(1, 7), BRW_REGISTER_TYPE_UD));
+         if (shader->stage != MESA_SHADER_FRAGMENT) {
+            return src_reg(0xffff);
+         } else if (((brw_wm_prog_data *)shader->stage_prog_data)->uses_kill) {
+            return brw_flag_reg(0, 1);
+         } else {
+            return retype(brw_vec1_grf(1, 7), BRW_REGISTER_TYPE_UD);
+         }
       }
 
       /**
-- 
2.4.9