glsl: Add conditional-select IR.

It's a ?: that operates per-component on vectors. Will be used in
upcoming lowering pass for ldexp and the implementation of frexp.

 csel(selector, a, b):
   per-component result = selector ? a : b

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/glsl/ir.cpp

@@ -436,6 +436,7 @@ ir_expression::ir_expression(int op, ir_rvalue *op0, ir_rvalue *op1,
       break;
 
    case ir_triop_bfi:
+   case ir_triop_csel:
       this->type = op1->type;
       break;
 
@@ -553,6 +554,7 @@ static const char *const operator_strs[] = {
    "vector_extract",
    "fma",
    "lrp",
+   "csel",
    "bfi",
    "bitfield_extract",
    "vector_insert",

src/glsl/ir.h

@@ -1196,6 +1196,18 @@ enum ir_expression_operation {
 
    ir_triop_lrp,
 
+   /**
+    * \name Conditional Select
+    *
+    * A vector conditional select instruction (like ?:, but operating per-
+    * component on vectors).
+    *
+    * \see lower_instructions_visitor::ldexp_to_arith
+    */
+   /*@{*/
+   ir_triop_csel,
+   /*@}*/
+
    /**
     * \name Second half of a lowered bitfieldInsert() operation.
     *

src/glsl/ir_builder.cpp

@@ -492,6 +492,12 @@ lrp(operand x, operand y, operand a)
    return expr(ir_triop_lrp, x, y, a);
 }
 
+ir_expression *
+csel(operand a, operand b, operand c)
+{
+   return expr(ir_triop_csel, a, b, c);
+}
+
 ir_expression *
 bitfield_insert(operand a, operand b, operand c, operand d)
 {

src/glsl/ir_builder.h

@@ -183,6 +183,7 @@ ir_expression *b2f(operand a);
 
 ir_expression *fma(operand a, operand b, operand c);
 ir_expression *lrp(operand x, operand y, operand a);
+ir_expression *csel(operand a, operand b, operand c);
 ir_expression *bitfield_insert(operand a, operand b, operand c, operand d);
 
 ir_swizzle *swizzle(operand a, int swizzle, int components);

src/glsl/ir_constant_expression.cpp

@@ -395,6 +395,7 @@ ir_expression::constant_expression_value(struct hash_table *variable_context)
       case ir_binop_lshift:
       case ir_binop_rshift:
       case ir_binop_vector_extract:
+      case ir_triop_csel:
       case ir_triop_bitfield_extract:
          break;
 
@@ -1399,6 +1400,13 @@ ir_expression::constant_expression_value(struct hash_table *variable_context)
       break;
    }
 
+   case ir_triop_csel:
+      for (unsigned c = 0; c < components; c++) {
+         data.u[c] = op[0]->value.b[c] ? op[1]->value.u[c]
+                                       : op[2]->value.u[c];
+      }
+      break;
+
    case ir_triop_vector_insert: {
       const unsigned idx = op[2]->value.u[0];
 

src/glsl/ir_validate.cpp

@@ -529,6 +529,13 @@ ir_validate::visit_leave(ir_expression *ir)
       assert(ir->operands[2]->type == ir->operands[0]->type || ir->operands[2]->type == glsl_type::float_type);
       break;
 
+   case ir_triop_csel:
+      assert(ir->operands[0]->type->base_type == GLSL_TYPE_BOOL);
+      assert(ir->type->vector_elements == ir->operands[0]->type->vector_elements);
+      assert(ir->type == ir->operands[1]->type);
+      assert(ir->type == ir->operands[2]->type);
+      break;
+
    case ir_triop_bfi:
       assert(ir->operands[0]->type->is_integer());
       assert(ir->operands[1]->type == ir->operands[2]->type);

src/mesa/program/ir_to_mesa.cpp

@@ -1497,6 +1497,7 @@ ir_to_mesa_visitor::visit(ir_expression *ir)
    case ir_triop_bitfield_extract:
    case ir_triop_vector_insert:
    case ir_quadop_bitfield_insert:
+   case ir_triop_csel:
       assert(!"not supported");
       break;
 

src/mesa/state_tracker/st_glsl_to_tgsi.cpp

@@ -1979,6 +1979,7 @@ glsl_to_tgsi_visitor::visit(ir_expression *ir)
    case ir_quadop_vector:
    case ir_binop_vector_extract:
    case ir_triop_vector_insert:
+   case ir_triop_csel:
       /* This operation is not supported, or should have already been handled.
        */
       assert(!"Invalid ir opcode in glsl_to_tgsi_visitor::visit()");