Hi!

When discussing PR111369 with Andrew Pinski, I've realized that
I haven't added BITINT_TYPE handling to range_check_type.  Right now
(unsigned) max + 1 == (unsigned) min for signed _BitInt,l so I think we
don't need to do the extra hops for BITINT_TYPE (though possibly we don't
need them for INTEGER_TYPE either in the two's complement word and we don't
support anything else, though I really don't know if Ada or some other
FEs don't create weird INTEGER_TYPEs).
And, also I think it is undesirable when being asked for signed_type_for
of unsigned _BitInt(1) (which is valid) to get signed _BitInt(1) (which is
invalid, the standard only allows signed _BitInt(2) and larger), so the
patch returns 1-bit signed INTEGER_TYPE for those cases.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2023-09-11  Jakub Jelinek  <ja...@redhat.com>

gcc/
        * tree.cc (signed_or_unsigned_type_for): Return INTEGER_TYPE for
        signed variant of unsigned _BitInt(1).
        * fold-const.cc (range_check_type): Handle BITINT_TYPE like
        OFFSET_TYPE.
gcc/c-family/
        * c-common.cc (c_common_signed_or_unsigned_type): Return INTEGER_TYPE
        for signed variant of unsigned _BitInt(1).

--- gcc/tree.cc.jj      2023-09-06 17:50:30.707589026 +0200
+++ gcc/tree.cc 2023-09-11 16:24:58.749625569 +0200
@@ -11096,7 +11096,7 @@ signed_or_unsigned_type_for (int unsigne
   else
     return NULL_TREE;
 
-  if (TREE_CODE (type) == BITINT_TYPE)
+  if (TREE_CODE (type) == BITINT_TYPE && (unsignedp || bits > 1))
     return build_bitint_type (bits, unsignedp);
   return build_nonstandard_integer_type (bits, unsignedp);
 }
--- gcc/c-family/c-common.cc.jj 2023-09-06 17:34:24.467254960 +0200
+++ gcc/c-family/c-common.cc    2023-09-11 16:24:07.873300311 +0200
@@ -2739,7 +2739,9 @@ c_common_signed_or_unsigned_type (int un
       || TYPE_UNSIGNED (type) == unsignedp)
     return type;
 
-  if (TREE_CODE (type) == BITINT_TYPE)
+  if (TREE_CODE (type) == BITINT_TYPE
+      /* signed _BitInt(1) is invalid, avoid creating that.  */
+      && (unsignedp || TYPE_PRECISION (type) > 1))
     return build_bitint_type (TYPE_PRECISION (type), unsignedp);
 
 #define TYPE_OK(node)                                                      \
--- gcc/fold-const.cc.jj        2023-09-11 11:05:47.473728473 +0200
+++ gcc/fold-const.cc   2023-09-11 16:28:06.052141516 +0200
@@ -5565,7 +5565,12 @@ range_check_type (tree etype)
       else
        return NULL_TREE;
     }
-  else if (POINTER_TYPE_P (etype) || TREE_CODE (etype) == OFFSET_TYPE)
+  else if (POINTER_TYPE_P (etype)
+          || TREE_CODE (etype) == OFFSET_TYPE
+          /* Right now all BITINT_TYPEs satisfy
+             (unsigned) max + 1 == (unsigned) min, so no need to verify
+             that like for INTEGER_TYPEs.  */
+          || TREE_CODE (etype) == BITINT_TYPE)
     etype = unsigned_type_for (etype);
   return etype;
 }

        Jakub

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