From: Aaron Sawdey <acsaw...@linux.ibm.com>

Richard,
  Thanks for the review. I think I have resolved everything, as follows:

* I was able to remove the const_tiny_rtx initialization for
MODE_OPAQUE.  If that becomes a problem it's a pretty simple matter to
use an UNSPEC to assign a constant to an opaque mode if necessary. The
whole point of this exercise was not to have this thing treated as an
integral type so I think it's best to leave this out if at all
possible.

* I ended up adding a precision to opaque after I had put in that hack
in get_nonzero_bits(). Now that it has a precision (equal to bitsize
as you say) this is no longer needed. The underlying problem there was
that without a precision, you ended up returning wi::shwi(-1,0) which
did not get treated as -1.

* I have documented OPAQUE_TYPE in generic.texi and MODE_OPAQUE in
rtl.texi.

OK for trunk if bootstrap/regtest passes on x86_64 and ppc64le?

Thanks,
    Aaron

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            |  1 +
 gcc/doc/generic.texi    |  8 ++++++++
 gcc/doc/rtl.texi        |  6 ++++++
 gcc/genmodes.c          | 22 ++++++++++++++++++++++
 gcc/ira.c               |  4 +++-
 gcc/machmode.def        |  3 +++
 gcc/machmode.h          |  4 ++++
 gcc/mode-classes.def    |  3 ++-
 gcc/stor-layout.c       |  3 +++
 gcc/tree-pretty-print.c |  1 +
 gcc/tree.c              |  1 +
 gcc/tree.def            |  6 ++++++
 gcc/tree.h              |  3 +++
 13 files changed, 63 insertions(+), 2 deletions(-)

diff --git a/gcc/dbxout.c b/gcc/dbxout.c
index 5a20fdecdcc..eaee2f19ce0 100644
--- a/gcc/dbxout.c
+++ b/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
diff --git a/gcc/doc/generic.texi b/gcc/doc/generic.texi
index 7373266c69f..7e7b74c6c8b 100644
--- a/gcc/doc/generic.texi
+++ b/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 use 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.
 
diff --git a/gcc/doc/rtl.texi b/gcc/doc/rtl.texi
index 22af5731bb6..cf892d425a2 100644
--- a/gcc/doc/rtl.texi
+++ b/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 moves between registers/memory. 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
diff --git a/gcc/genmodes.c b/gcc/genmodes.c
index bd78310ea24..34b52fe41d6 100644
--- a/gcc/genmodes.c
+++ b/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__)
 
diff --git a/gcc/ira.c b/gcc/ira.c
index 050405f1833..e5f9a080e4d 100644
--- a/gcc/ira.c
+++ b/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);
 
diff --git a/gcc/machmode.def b/gcc/machmode.def
index e4c9b4b5d98..6f8c6855aca 100644
--- a/gcc/machmode.def
+++ b/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
diff --git a/gcc/machmode.h b/gcc/machmode.h
index fbeefc24804..bb3a5c6c27e 100644
--- a/gcc/machmode.h
+++ b/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                           \
diff --git a/gcc/mode-classes.def b/gcc/mode-classes.def
index f181def05ae..b78a715ba59 100644
--- a/gcc/mode-classes.def
+++ b/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 */
diff --git a/gcc/stor-layout.c b/gcc/stor-layout.c
index dff81d1c24f..ee1cf55df90 100644
--- a/gcc/stor-layout.c
+++ b/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 ();
diff --git a/gcc/tree-pretty-print.c b/gcc/tree-pretty-print.c
index bd60d74d1af..c19e485e75a 100644
--- a/gcc/tree-pretty-print.c
+++ b/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;
diff --git a/gcc/tree.c b/gcc/tree.c
index 9260772b846..45b5a64c74c 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -837,6 +837,7 @@ 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:
diff --git a/gcc/tree.def b/gcc/tree.def
index 6c53fe1bf67..462672f2c69 100644
--- a/gcc/tree.def
+++ b/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 */
 
diff --git a/gcc/tree.h b/gcc/tree.h
index caf6287f909..70570522330 100644
--- a/gcc/tree.h
+++ b/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
-- 
2.18.4

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