nir: fix denorms in unpack_half_1x16()

According to VK_KHR_shader_float_controls:

"Denormalized values obtained via unpacking an integer into a vector
 of values with smaller bit width and interpreting those values as
 floating-point numbers must: be flushed to zero, unless the entry
 point is declared with the code:DenormPreserve execution mode."

v2:
- Add nir_op_unpack_half_2x16_flush_to_zero opcode (Connor).

v3:
- Adapt to use the new NIR lowering framework (Andres).

v4:
- Updated to renamed shader info member and enum values (Andres).

v5:
- Simplify flags logic operations (Caio).

Signed-off-by: Samuel Iglesias Gonsálvez <[email protected]>
Signed-off-by: Andres Gomez <[email protected]>
Reviewed-by: Connor Abbott <[email protected]> [v2]

1 files changed, 12 insertions, 2 deletions

diff --git a/src/compiler/nir/nir_lower_alu_to_scalar.c b/src/compiler/nir/nir_lower_alu_to_scalar.c
index bcd92908253..c0b7cc604ef 100644
--- a/src/compiler/nir/nir_lower_alu_to_scalar.c
+++ b/src/compiler/nir/nir_lower_alu_to_scalar.c
@@ -145,13 +145,23 @@ lower_alu_instr_scalar(nir_builder *b, nir_instr *instr, void *_data)
        */
       return NULL;
 
+   case nir_op_unpack_half_2x16_flush_to_zero:
    case nir_op_unpack_half_2x16: {
       if (!b->shader->options->lower_unpack_half_2x16)
          return NULL;
 
       nir_ssa_def *packed = nir_ssa_for_alu_src(b, alu, 0);
-      return nir_vec2(b, nir_unpack_half_2x16_split_x(b, packed),
-                         nir_unpack_half_2x16_split_y(b, packed));
+      if (alu->op == nir_op_unpack_half_2x16_flush_to_zero) {
+          return nir_vec2(b,
+                          nir_unpack_half_2x16_split_x_flush_to_zero(b,
+                                                                     packed),
+                          nir_unpack_half_2x16_split_y_flush_to_zero(b,
+                                                                     packed));
+      } else {
+          return nir_vec2(b,
+                          nir_unpack_half_2x16_split_x(b, packed),
+                          nir_unpack_half_2x16_split_y(b, packed));
+      }
    }
 
    case nir_op_pack_uvec2_to_uint: {