nir: Introduce nir_intrinsic_discard_if.

This is a conditional discard, which takes a boolean source.

Note that we don't generate ir_discard::condition today, so this
shouldn't break drivers (since none implement this intrinsic yet).

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Connor Abbott <[email protected]>
Reviewed-by: Matt Turner <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

2 files changed, 10 insertions, 2 deletions

diff --git a/src/glsl/nir/glsl_to_nir.cpp b/src/glsl/nir/glsl_to_nir.cpp
index 544d0d93282..adef19c80a2 100644
--- a/src/glsl/nir/glsl_to_nir.cpp
+++ b/src/glsl/nir/glsl_to_nir.cpp
@@ -563,8 +563,14 @@ nir_visitor::visit(ir_discard *ir)
     * discards will be immediately followed by a return.
     */
 
-   nir_intrinsic_instr *discard =
-      nir_intrinsic_instr_create(this->shader, nir_intrinsic_discard);
+   nir_intrinsic_instr *discard;
+   if (ir->condition) {
+      discard = nir_intrinsic_instr_create(this->shader,
+                                           nir_intrinsic_discard_if);
+      discard->src[0] = evaluate_rvalue(ir->condition);
+   } else {
+      discard = nir_intrinsic_instr_create(this->shader, nir_intrinsic_discard);
+   }
    nir_instr_insert_after_cf_list(this->cf_node_list, &discard->instr);
 }
 
diff --git a/src/glsl/nir/nir_intrinsics.h b/src/glsl/nir/nir_intrinsics.h
index d94866c8597..3bf102fc15c 100644
--- a/src/glsl/nir/nir_intrinsics.h
+++ b/src/glsl/nir/nir_intrinsics.h
@@ -68,6 +68,8 @@ INTRINSIC(interp_var_at_offset, 1, ARR(2), true, 0, 1, 0,
 #define BARRIER(name) INTRINSIC(name, 0, ARR(), false, 0, 0, 0, 0)
 
 BARRIER(discard)
+/** A conditional discard, with a single boolean source. */
+INTRINSIC(discard_if, 1, ARR(1), false, 0, 0, 0, 0)
 
 INTRINSIC(emit_vertex,   0, ARR(), false, 0, 0, 1, 0)
 INTRINSIC(end_primitive, 0, ARR(), false, 0, 0, 1, 0)