glsl: Support the 'invariant(all)' pragma

Previously the 'STDGL invariant(all)' pragma added in GLSL 1.20 was
simply ignored by the compiler.  This adds support for setting all
variable invariant.

In GLSL 1.10 and GLSL ES 1.00 the pragma is ignored, per the specs,
but a warning is generated.

Fixes piglit test glsl-invariant-pragma and bugzilla #31925.

NOTE: This is a candidate for the 7.9 and 7.10 branches.

src/glsl/ast_to_hir.cpp

@@ -1852,6 +1852,23 @@ apply_type_qualifier_to_variable(const struct ast_type_qualifier *qual,
    else if (qual->flags.q.uniform)
       var->mode = ir_var_uniform;
 
+   if (state->all_invariant && (state->current_function == NULL)) {
+      switch (state->target) {
+      case vertex_shader:
+	 if (var->mode == ir_var_out)
+	    var->invariant = true;
+	 break;
+      case geometry_shader:
+	 if ((var->mode == ir_var_in) || (var->mode == ir_var_out))
+	    var->invariant = true;
+	 break;
+      case fragment_shader:
+	 if (var->mode == ir_var_in)
+	    var->invariant = true;
+	 break;
+      }
+   }
+
    if (qual->flags.q.flat)
       var->interpolation = ir_var_flat;
    else if (qual->flags.q.noperspective)

src/glsl/glsl_lexer.lpp

@@ -145,6 +145,10 @@ HASH		^{SPC}#{SPC}
 				  BEGIN PP;
 				  return PRAGMA_OPTIMIZE_OFF;
 				}
+^{SPC}#{SPC}pragma{SPCP}STDGL{SPCP}invariant{SPC}\({SPC}all{SPC}\) {
+				  BEGIN PP;
+				  return PRAGMA_INVARIANT_ALL;
+				}
 ^{SPC}#{SPC}pragma{SPCP}	{ BEGIN PRAGMA; }
 
 <PRAGMA>\n			{ BEGIN 0; yylineno++; yycolumn = 0; }

src/glsl/glsl_parser.ypp

@@ -108,6 +108,7 @@
 %token VERSION EXTENSION LINE COLON EOL INTERFACE OUTPUT
 %token PRAGMA_DEBUG_ON PRAGMA_DEBUG_OFF
 %token PRAGMA_OPTIMIZE_ON PRAGMA_OPTIMIZE_OFF
+%token PRAGMA_INVARIANT_ALL
 %token LAYOUT_TOK
 
    /* Reserved words that are not actually used in the grammar.
@@ -241,6 +242,19 @@ pragma_statement:
 	| PRAGMA_DEBUG_OFF EOL
 	| PRAGMA_OPTIMIZE_ON EOL
 	| PRAGMA_OPTIMIZE_OFF EOL
+	| PRAGMA_INVARIANT_ALL EOL
+	{
+	   if (state->language_version < 120) {
+	      _mesa_glsl_warning(& @1, state,
+				 "pragma `invariant(all)' not supported in "
+				 "GLSL%s %d.%02d",
+				 state->es_shader ? " ES" : "",
+				 state->language_version / 100,
+				 state->language_version % 100);
+	   } else {
+	      state->all_invariant = true;
+	   }
+	}
 	;
 
 extension_statement_list:

src/glsl/glsl_parser_extras.h

@@ -108,6 +108,13 @@ struct _mesa_glsl_parse_state {
    /** Was there an error during compilation? */
    bool error;
 
+   /**
+    * Are all shader inputs / outputs invariant?
+    *
+    * This is set when the 'STDGL invariant(all)' pragma is used.
+    */
+   bool all_invariant;
+
    /** Loop or switch statement containing the current instructions. */
    class ir_instruction *loop_or_switch_nesting;
    class ast_iteration_statement *loop_or_switch_nesting_ast;