i965/fs: Handle conditional discards.

The discard condition tells us which channels we want killed.  We want
to invert that condition to get the channels that should survive (remain
live) in f0.1.  Emit a CMP to negate it.

Nothing generates these today, but that will change shortly.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index 03e9ee80e137b409f33612ff41a0d26f67e0a239..388e63601611d9fd7e33118f36bb9db64b0bab7a 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -1258,16 +1258,22 @@ fs_visitor::nir_emit_intrinsic(nir_intrinsic_instr *instr)
    bool has_indirect = false;
 
    switch (instr->intrinsic) {
-   case nir_intrinsic_discard: {
+   case nir_intrinsic_discard:
+   case nir_intrinsic_discard_if: {
       /* We track our discarded pixels in f0.1.  By predicating on it, we can
-       * update just the flag bits that aren't yet discarded.  By emitting a
-       * CMP of g0 != g0, all our currently executing channels will get turned
-       * off.
+       * update just the flag bits that aren't yet discarded.  If there's no
+       * condition, we emit a CMP of g0 != g0, so all currently executing
+       * channels will get turned off.
        */
-      fs_reg some_reg = fs_reg(retype(brw_vec8_grf(0, 0),
-                                    BRW_REGISTER_TYPE_UW));
-      fs_inst *cmp = emit(CMP(reg_null_f, some_reg, some_reg,
-                              BRW_CONDITIONAL_NZ));
+      fs_inst *cmp;
+      if (instr->intrinsic == nir_intrinsic_discard_if) {
+         cmp = emit(CMP(reg_null_f, get_nir_src(instr->src[0]),
+                        fs_reg(0), BRW_CONDITIONAL_Z));
+      } else {
+         fs_reg some_reg = fs_reg(retype(brw_vec8_grf(0, 0),
+                                       BRW_REGISTER_TYPE_UW));
+         cmp = emit(CMP(reg_null_f, some_reg, some_reg, BRW_CONDITIONAL_NZ));
+      }
       cmp->predicate = BRW_PREDICATE_NORMAL;
       cmp->flag_subreg = 1;
 

diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index 7c447af489ed595d3c303e7d72b66fbc17ece4a6..13a3bf29da81b8d2f90d4e2c1f8036295dbd8658 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -2415,17 +2415,20 @@ fs_visitor::visit(ir_swizzle *ir)
 void
 fs_visitor::visit(ir_discard *ir)
 {
-   assert(ir->condition == NULL); /* FINISHME */
-
    /* We track our discarded pixels in f0.1.  By predicating on it, we can
-    * update just the flag bits that aren't yet discarded.  By emitting a
-    * CMP of g0 != g0, all our currently executing channels will get turned
-    * off.
+    * update just the flag bits that aren't yet discarded.  If there's no
+    * condition, we emit a CMP of g0 != g0, so all currently executing
+    * channels will get turned off.
     */
-   fs_reg some_reg = fs_reg(retype(brw_vec8_grf(0, 0),
-                                   BRW_REGISTER_TYPE_UW));
-   fs_inst *cmp = emit(CMP(reg_null_f, some_reg, some_reg,
-                           BRW_CONDITIONAL_NZ));
+   fs_inst *cmp;
+   if (ir->condition) {
+      ir->condition->accept(this);
+      cmp = emit(CMP(reg_null_f, this->result, fs_reg(0), BRW_CONDITIONAL_Z));
+   } else {
+      fs_reg some_reg = fs_reg(retype(brw_vec8_grf(0, 0),
+                                      BRW_REGISTER_TYPE_UW));
+      cmp = emit(CMP(reg_null_f, some_reg, some_reg, BRW_CONDITIONAL_NZ));
+   }
    cmp->predicate = BRW_PREDICATE_NORMAL;
    cmp->flag_subreg = 1;