glsl: Add ir_demote

To represent the new `demote` keyword when using
EXT_demote_to_helper_invocation extension.  Most of the changes are to
include it in the visitors.

Demote is not considered a control flow, so also include an empty
visit member function in ir_control_flow_visitor.

Only NIR actually supports `demote`, so assert the translations for
TGSI and Mesa's gl_program -- since the demote is not expected to
appear for those.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/glsl/glsl_to_nir.cpp

@@ -63,6 +63,7 @@ public:
    virtual void visit(ir_loop *);
    virtual void visit(ir_if *);
    virtual void visit(ir_discard *);
+   virtual void visit(ir_demote *);
    virtual void visit(ir_loop_jump *);
    virtual void visit(ir_return *);
    virtual void visit(ir_call *);
@@ -775,6 +776,15 @@ nir_visitor::visit(ir_discard *ir)
    nir_builder_instr_insert(&b, &discard->instr);
 }
 
+void
+nir_visitor::visit(ir_demote *ir)
+{
+   nir_intrinsic_instr *demote =
+      nir_intrinsic_instr_create(this->shader, nir_intrinsic_demote);
+
+   nir_builder_instr_insert(&b, &demote->instr);
+}
+
 void
 nir_visitor::visit(ir_emit_vertex *ir)
 {

src/compiler/glsl/ir.h

@@ -74,6 +74,7 @@ enum ir_node_type {
    ir_type_loop_jump,
    ir_type_return,
    ir_type_discard,
+   ir_type_demote,
    ir_type_emit_vertex,
    ir_type_end_primitive,
    ir_type_barrier,
@@ -1804,6 +1805,28 @@ public:
 /*@}*/
 
 
+/**
+ * IR instruction representing demote statements from
+ * GL_EXT_demote_to_helper_invocation.
+ */
+class ir_demote : public ir_instruction {
+public:
+   ir_demote()
+      : ir_instruction(ir_type_demote)
+   {
+   }
+
+   virtual ir_demote *clone(void *mem_ctx, struct hash_table *ht) const;
+
+   virtual void accept(ir_visitor *v)
+   {
+      v->visit(this);
+   }
+
+   virtual ir_visitor_status accept(ir_hierarchical_visitor *);
+};
+
+
 /**
  * Texture sampling opcodes used in ir_texture
  */

src/compiler/glsl/ir_clone.cpp

@@ -102,6 +102,12 @@ ir_discard::clone(void *mem_ctx, struct hash_table *ht) const
    return new(mem_ctx) ir_discard(new_condition);
 }
 
+ir_demote *
+ir_demote::clone(void *mem_ctx, struct hash_table *ht) const
+{
+   return new(mem_ctx) ir_demote();
+}
+
 ir_loop_jump *
 ir_loop_jump::clone(void *mem_ctx, struct hash_table *ht) const
 {

src/compiler/glsl/ir_hierarchical_visitor.cpp

@@ -304,6 +304,24 @@ ir_hierarchical_visitor::visit_leave(ir_discard *ir)
    return visit_continue;
 }
 
+ir_visitor_status
+ir_hierarchical_visitor::visit_enter(ir_demote *ir)
+{
+   if (this->callback_enter != NULL)
+      this->callback_enter(ir, this->data_enter);
+
+   return visit_continue;
+}
+
+ir_visitor_status
+ir_hierarchical_visitor::visit_leave(ir_demote *ir)
+{
+   if (this->callback_leave != NULL)
+      this->callback_leave(ir, this->data_leave);
+
+   return visit_continue;
+}
+
 ir_visitor_status
 ir_hierarchical_visitor::visit_enter(ir_if *ir)
 {

src/compiler/glsl/ir_hierarchical_visitor.h

@@ -133,6 +133,8 @@ public:
    virtual ir_visitor_status visit_leave(class ir_return *);
    virtual ir_visitor_status visit_enter(class ir_discard *);
    virtual ir_visitor_status visit_leave(class ir_discard *);
+   virtual ir_visitor_status visit_enter(class ir_demote *);
+   virtual ir_visitor_status visit_leave(class ir_demote *);
    virtual ir_visitor_status visit_enter(class ir_if *);
    virtual ir_visitor_status visit_leave(class ir_if *);
    virtual ir_visitor_status visit_enter(class ir_emit_vertex *);

src/compiler/glsl/ir_hv_accept.cpp

@@ -378,6 +378,18 @@ ir_discard::accept(ir_hierarchical_visitor *v)
 }
 
 
+ir_visitor_status
+ir_demote::accept(ir_hierarchical_visitor *v)
+{
+   ir_visitor_status s = v->visit_enter(this);
+
+   if (s != visit_continue)
+      return (s == visit_continue_with_parent) ? visit_continue : s;
+
+   return v->visit_leave(this);
+}
+
+
 ir_visitor_status
 ir_if::accept(ir_hierarchical_visitor *v)
 {

src/compiler/glsl/ir_print_visitor.cpp

@@ -564,6 +564,13 @@ ir_print_visitor::visit(ir_discard *ir)
 }
 
 
+void
+ir_print_visitor::visit(ir_demote *ir)
+{
+   fprintf(f, "(demote)");
+}
+
+
 void
 ir_print_visitor::visit(ir_if *ir)
 {

src/compiler/glsl/ir_print_visitor.h

@@ -63,6 +63,7 @@ public:
    virtual void visit(ir_call *);
    virtual void visit(ir_return *);
    virtual void visit(ir_discard *);
+   virtual void visit(ir_demote *);
    virtual void visit(ir_if *);
    virtual void visit(ir_loop *);
    virtual void visit(ir_loop_jump *);

src/compiler/glsl/ir_visitor.h

@@ -59,6 +59,7 @@ public:
    virtual void visit(class ir_call *) = 0;
    virtual void visit(class ir_return *) = 0;
    virtual void visit(class ir_discard *) = 0;
+   virtual void visit(class ir_demote *) = 0;
    virtual void visit(class ir_if *) = 0;
    virtual void visit(class ir_loop *) = 0;
    virtual void visit(class ir_loop_jump *) = 0;
@@ -83,6 +84,7 @@ public:
    virtual void visit(class ir_assignment *) {}
    virtual void visit(class ir_constant *) {}
    virtual void visit(class ir_call *) {}
+   virtual void visit(class ir_demote *) {}
    virtual void visit(class ir_emit_vertex *) {}
    virtual void visit(class ir_end_primitive *) {}
    virtual void visit(class ir_barrier *) {}

src/mesa/program/ir_to_mesa.cpp

@@ -252,6 +252,7 @@ public:
    virtual void visit(ir_call *);
    virtual void visit(ir_return *);
    virtual void visit(ir_discard *);
+   virtual void visit(ir_demote *);
    virtual void visit(ir_texture *);
    virtual void visit(ir_if *);
    virtual void visit(ir_emit_vertex *);
@@ -2201,6 +2202,12 @@ ir_to_mesa_visitor::visit(ir_discard *ir)
    emit(ir, OPCODE_KIL, undef_dst, this->result);
 }
 
+void
+ir_to_mesa_visitor::visit(ir_demote *ir)
+{
+   assert(!"demote statement unsupported");
+}
+
 void
 ir_to_mesa_visitor::visit(ir_if *ir)
 {

src/mesa/state_tracker/st_glsl_to_tgsi.cpp

@@ -284,6 +284,7 @@ public:
    virtual void visit(ir_call *);
    virtual void visit(ir_return *);
    virtual void visit(ir_discard *);
+   virtual void visit(ir_demote *);
    virtual void visit(ir_texture *);
    virtual void visit(ir_if *);
    virtual void visit(ir_emit_vertex *);
@@ -4626,6 +4627,12 @@ glsl_to_tgsi_visitor::visit(ir_discard *ir)
    }
 }
 
+void
+glsl_to_tgsi_visitor::visit(ir_demote *ir)
+{
+   assert(!"demote statement unsupported");
+}
+
 void
 glsl_to_tgsi_visitor::visit(ir_if *ir)
 {