nir: Add and use algebraic property "is selection"

There are several places that should have supported the various sized
versions of bcsel and the various nir_op_[fi]csel_* opcodes.  Rather
than enumerate the whole list, add a property.

v2: Make the comment for NIR_OP_IS_SELECTION more descriptive.
Suggested by Jason.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17048>

src/compiler/nir/nir.h

@@ -1355,6 +1355,13 @@ typedef enum {
     * Operation is associative
     */
    NIR_OP_IS_ASSOCIATIVE = (1 << 1),
+
+   /**
+    * Operation where src[0] is used to select src[1] on true or src[2] false.
+    * src[0] may be Boolean, or it may be another type used in an implicit
+    * comparison.
+    */
+   NIR_OP_IS_SELECTION = (1 << 2),
 } nir_op_algebraic_property;
 
 /* vec16 is the widest ALU op in NIR, making the max number of input of ALU
@@ -1419,6 +1426,12 @@ typedef struct nir_op_info {
 /** Metadata for each nir_op, indexed by opcode */
 extern const nir_op_info nir_op_infos[nir_num_opcodes];
 
+static inline bool
+nir_op_is_selection(nir_op op)
+{
+   return (nir_op_infos[op].algebraic_properties & NIR_OP_IS_SELECTION) != 0;
+}
+
 typedef struct nir_alu_instr {
    /** Base instruction */
    nir_instr instr;

src/compiler/nir/nir_opcodes.py

@@ -146,6 +146,7 @@ def type_base_type(type_):
 # sources.
 _2src_commutative = "2src_commutative "
 associative = "associative "
+selection = "selection "
 
 # global dictionary of opcodes
 opcodes = {}
@@ -1008,22 +1009,22 @@ triop("iadd3", tint, _2src_commutative + associative, "src0 + src1 + src2")
 # component on vectors). There are two versions, one for floating point
 # bools (0.0 vs 1.0) and one for integer bools (0 vs ~0).
 
-triop("fcsel", tfloat32, "", "(src0 != 0.0f) ? src1 : src2")
+triop("fcsel", tfloat32, selection, "(src0 != 0.0f) ? src1 : src2")
 
 opcode("bcsel", 0, tuint, [0, 0, 0],
-       [tbool1, tuint, tuint], False, "", "src0 ? src1 : src2")
+       [tbool1, tuint, tuint], False, selection, "src0 ? src1 : src2")
 opcode("b8csel", 0, tuint, [0, 0, 0],
-       [tbool8, tuint, tuint], False, "", "src0 ? src1 : src2")
+       [tbool8, tuint, tuint], False, selection, "src0 ? src1 : src2")
 opcode("b16csel", 0, tuint, [0, 0, 0],
-       [tbool16, tuint, tuint], False, "", "src0 ? src1 : src2")
+       [tbool16, tuint, tuint], False, selection, "src0 ? src1 : src2")
 opcode("b32csel", 0, tuint, [0, 0, 0],
-       [tbool32, tuint, tuint], False, "", "src0 ? src1 : src2")
+       [tbool32, tuint, tuint], False, selection, "src0 ? src1 : src2")
 
-triop("i32csel_gt", tint32, "", "(src0 > 0) ? src1 : src2")
-triop("i32csel_ge", tint32, "", "(src0 >= 0) ? src1 : src2")
+triop("i32csel_gt", tint32, selection, "(src0 > 0) ? src1 : src2")
+triop("i32csel_ge", tint32, selection, "(src0 >= 0) ? src1 : src2")
 
-triop("fcsel_gt", tfloat32, "", "(src0 > 0.0f) ? src1 : src2")
-triop("fcsel_ge", tfloat32, "", "(src0 >= 0.0f) ? src1 : src2")
+triop("fcsel_gt", tfloat32, selection, "(src0 > 0.0f) ? src1 : src2")
+triop("fcsel_ge", tfloat32, selection, "(src0 >= 0.0f) ? src1 : src2")
 
 # SM5 bfi assembly
 triop("bfi", tuint32, "", """

src/compiler/nir/nir_opt_if.c

@@ -303,9 +303,7 @@ is_trivial_bcsel(const nir_instr *instr, bool allow_non_phi_src)
       return false;
 
    nir_alu_instr *const bcsel = nir_instr_as_alu(instr);
-   if (bcsel->op != nir_op_bcsel &&
-       bcsel->op != nir_op_b32csel &&
-       bcsel->op != nir_op_fcsel)
+   if (!nir_op_is_selection(bcsel->op))
       return false;
 
    for (unsigned i = 0; i < 3; i++) {

src/compiler/nir/nir_opt_undef.c

@@ -38,7 +38,7 @@
 static bool
 opt_undef_csel(nir_alu_instr *instr)
 {
-   if (instr->op != nir_op_bcsel && instr->op != nir_op_fcsel)
+   if (!nir_op_is_selection(instr->op))
       return false;
 
    assert(instr->dest.dest.is_ssa);