Add MODE_OPAQUE

After discussion with Richard Sandiford on IRC, he suggested adding a
new mode class MODE_OPAQUE to deal with the problems (PR 96791) we had
been having with POImode/PXImode in powerpc target. This patch is the
accumulation of changes I needed to make to add this and make it useable
for the purposes of what power10 MMA needed.

MODE_OPAQUE modes allow you to have modes for which you can just
define loads and stores. By design, optimization does not expect to
know how to do arithmetic or subregs on these modes. This allows us to
have modes for multi-register vector operations where we don't want to
open Pandora's Box and define general arithmetic operations.

This patch will be followed by a target specific patch to change the
powerpc power10 MMA builtins to use opaque modes, and will also let use
use the vector pair loads/stores defined with that in the inline expansion
of memcpy/memmove, allowing me to fix PR 96791.

gcc/ChangeLog
	PR target/96791
	* mode-classes.def: Add MODE_OPAQUE.
	* machmode.def: Add OPAQUE_MODE.
	* tree.def: Add OPAQUE_TYPE for types that will use
	MODE_OPAQUE.
	* doc/generic.texi: Document OPAQUE_TYPE.
	* doc/rtl.texi: Document MODE_OPAQUE.
	* machmode.h: Add OPAQUE_MODE_P().
	* genmodes.c (complete_mode): Add MODE_OPAQUE.
	(opaque_mode): New function.
	* tree.c (tree_code_size): Add OPAQUE_TYPE.
	* tree.h: Add OPAQUE_TYPE_P().
	* stor-layout.c (int_mode_for_mode): Treat MODE_OPAQUE modes
	like BLKmode.
	* ira.c (find_moveable_pseudos): Treat MODE_OPAQUE modes more
	like integer/float modes here.
	* dbxout.c (dbxout_type): Treat OPAQUE_TYPE like VOID_TYPE.
	* tree-pretty-print.c (dump_generic_node): Treat OPAQUE_TYPE
	like like other types.

gcc/dbxout.c

@@ -1963,6 +1963,7 @@ dbxout_type (tree type, int full)
     case VOID_TYPE:
     case NULLPTR_TYPE:
     case LANG_TYPE:
+    case OPAQUE_TYPE:
       /* For a void type, just define it as itself; i.e., "5=5".
 	 This makes us consider it defined
 	 without saying what it is.  The debugger will make it

gcc/doc/generic.texi

@@ -302,6 +302,7 @@ The elements are indexed from zero.
 @tindex ARRAY_TYPE
 @tindex RECORD_TYPE
 @tindex UNION_TYPE
+@tindex OPAQUE_TYPE
 @tindex UNKNOWN_TYPE
 @tindex OFFSET_TYPE
 @findex TYPE_UNQUALIFIED
@@ -487,6 +488,13 @@ assigned to that constant.  These constants will appear in the order in
 which they were declared.  The @code{TREE_TYPE} of each of these
 constants will be the type of enumeration type itself.
 
+@item OPAQUE_TYPE
+Used for things that have a @code{MODE_OPAQUE} mode class in the
+backend. Opaque types have a size and precision, and can be held in
+memory or registers. They are used when we do not want the compiler to
+make assumptions about the availability of other operations as would
+happen with integer types.
+
 @item BOOLEAN_TYPE
 Used to represent the @code{bool} type.
 

gcc/doc/rtl.texi

@@ -1406,6 +1406,12 @@ Pointer bounds modes.  Used to represent values of pointer bounds type.
 Operations in these modes may be executed as NOPs depending on hardware
 features and environment setup.
 
+@findex MODE_OPAQUE
+@item MODE_OPAQUE
+This is a mode class for modes that don't want to provide operations
+other than register moves, memory moves, loads, stores, and
+@code{unspec}s. They have a size and precision and that's all.
+
 @findex MODE_RANDOM
 @item MODE_RANDOM
 This is a catchall mode class for modes which don't fit into the above

gcc/genmodes.c

@@ -358,6 +358,14 @@ complete_mode (struct mode_data *m)
       m->component = 0;
       break;
 
+    case MODE_OPAQUE:
+      /* Opaque modes have size and precision.  */
+      validate_mode (m, OPTIONAL, SET, UNSET, UNSET, UNSET);
+
+      m->ncomponents = 1;
+      m->component = 0;
+      break;
+
     case MODE_PARTIAL_INT:
       /* A partial integer mode uses ->component to say what the
 	 corresponding full-size integer mode is, and may also
@@ -588,6 +596,20 @@ make_int_mode (const char *name,
   m->precision = precision;
 }
 
+#define OPAQUE_MODE(N, B)			\
+  make_opaque_mode (#N, -1U, B, __FILE__, __LINE__)
+
+static void ATTRIBUTE_UNUSED
+make_opaque_mode (const char *name,
+		  unsigned int precision,
+		  unsigned int bytesize,
+		  const char *file, unsigned int line)
+{
+  struct mode_data *m = new_mode (MODE_OPAQUE, name, file, line);
+  m->bytesize = bytesize;
+  m->precision = precision;
+}
+
 #define FRACT_MODE(N, Y, F) \
 	make_fixed_point_mode (MODE_FRACT, #N, Y, 0, F, __FILE__, __LINE__)
 

gcc/ira.c

@@ -4666,7 +4666,9 @@ find_moveable_pseudos (void)
 		|| !DF_REF_INSN_INFO (def)
 		|| HARD_REGISTER_NUM_P (regno)
 		|| DF_REG_EQ_USE_COUNT (regno) > 0
-		|| (!INTEGRAL_MODE_P (mode) && !FLOAT_MODE_P (mode)))
+		|| (!INTEGRAL_MODE_P (mode)
+		    && !FLOAT_MODE_P (mode)
+		    && !OPAQUE_MODE_P (mode)))
 	      continue;
 	    def_insn = DF_REF_INSN (def);
 

gcc/machmode.def

@@ -153,6 +153,9 @@ along with GCC; see the file COPYING3.  If not see
         the element at index 0 occupying the lsb of the first byte in
         memory.  Only the lowest bit of each element is significant.
 
+     OPAQUE_MODE (NAME, BYTESIZE)
+        Create an opaque mode called NAME that is BYTESIZE bytes wide.
+
      COMPLEX_MODES (CLASS);
         For all modes presently declared in class CLASS, construct
 	corresponding complex modes.  Modes smaller than one byte

gcc/machmode.h

@@ -225,6 +225,10 @@ extern const unsigned char mode_class[NUM_MACHINE_MODES];
   (SIGNED_FIXED_POINT_MODE_P (MODE)		\
    || UNSIGNED_FIXED_POINT_MODE_P (MODE))
 
+/* Nonzero if MODE is opaque.  */
+#define OPAQUE_MODE_P(MODE)                     \
+    (GET_MODE_CLASS (MODE) == MODE_OPAQUE)
+
 /* Nonzero if CLASS modes can be widened.  */
 #define CLASS_HAS_WIDER_MODES_P(CLASS)         \
   (CLASS == MODE_INT                           \

gcc/mode-classes.def

@@ -36,4 +36,5 @@ along with GCC; see the file COPYING3.  If not see
   DEF_MODE_CLASS (MODE_VECTOR_UFRACT),	/* SIMD vectors */		   \
   DEF_MODE_CLASS (MODE_VECTOR_ACCUM),	/* SIMD vectors */		   \
   DEF_MODE_CLASS (MODE_VECTOR_UACCUM),	/* SIMD vectors */		   \
-  DEF_MODE_CLASS (MODE_VECTOR_FLOAT)
+  DEF_MODE_CLASS (MODE_VECTOR_FLOAT),                                      \
+  DEF_MODE_CLASS (MODE_OPAQUE)          /* opaque modes */

gcc/stor-layout.c

@@ -393,6 +393,9 @@ int_mode_for_mode (machine_mode mode)
     case MODE_VECTOR_UACCUM:
       return int_mode_for_size (GET_MODE_BITSIZE (mode), 0);
 
+    case MODE_OPAQUE:
+	return opt_scalar_int_mode ();
+
     case MODE_RANDOM:
       if (mode == BLKmode)
 	return opt_scalar_int_mode ();

gcc/tree-pretty-print.c

@@ -1708,6 +1708,7 @@ dump_generic_node (pretty_printer *pp, tree node, int spc, dump_flags_t flags,
     case VECTOR_TYPE:
     case ENUMERAL_TYPE:
     case BOOLEAN_TYPE:
+    case OPAQUE_TYPE:
       {
 	unsigned int quals = TYPE_QUALS (node);
 	enum tree_code_class tclass;

gcc/tree.c

@@ -864,6 +864,7 @@ tree_code_size (enum tree_code code)
 	case BOOLEAN_TYPE:
 	case INTEGER_TYPE:
 	case REAL_TYPE:
+	case OPAQUE_TYPE:
 	case POINTER_TYPE:
 	case REFERENCE_TYPE:
 	case NULLPTR_TYPE:

gcc/tree.def

@@ -250,6 +250,12 @@ DEFTREECODE (METHOD_TYPE, "method_type", tcc_type, 0)
    layout_type does not know how to lay this out,
    so the front-end must do so manually.  */
 DEFTREECODE (LANG_TYPE, "lang_type", tcc_type, 0)
+
+/* This is for types that will use MODE_OPAQUE in the back end.  They are meant
+   to be able to go in a register of some sort but are explicitly not to be
+   converted or operated on like INTEGER_TYPE.  They will have size and
+   alignment information only.  */
+DEFTREECODE (OPAQUE_TYPE, "opaque_type", tcc_type, 0)
 
 /* Expressions */
 

gcc/tree.h

@@ -625,6 +625,9 @@ extern void omp_clause_range_check_failed (const_tree, const char *, int,
 #define FUNC_OR_METHOD_TYPE_P(NODE) \
   (TREE_CODE (NODE) == FUNCTION_TYPE || TREE_CODE (NODE) == METHOD_TYPE)
 
+#define OPAQUE_TYPE_P(NODE) \
+    (TREE_CODE (NODE) == OPAQUE_TYPE)
+
 /* Define many boolean fields that all tree nodes have.  */
 
 /* In VAR_DECL, PARM_DECL and RESULT_DECL nodes, nonzero means address