genconditions: Add support for targets without non-trivial insn conditions

Somebody complained on IRC that when writing a new backend one can get
an error while compiling build/gencondmd.cc.
The problem is that when host compiler is g++ 3 or later (or when
bootstrapping), we compile it with g++ -std=c++11 -pedantic and
the generated insn_conditions array contains pairs
{ "cond", __builtin_constant_p (cond) ? (int) (cond) : -1 },
where cond is some non-trivial instruction condition.  Now if a target
uses "" for all the conditions (admittedly unlikely for non-trivial
target), the initializer for insn_conditions[] is {} and that is
pedantically rejected because C++ doesn't support zero-sized arrays.

The following patch fixes that by adding an artificial termination
element and skips that during the walk.

2022-05-04  Jakub Jelinek  <jakub@redhat.com>

	* genconditions.cc (write_conditions): Append a { nullptr, -1 }
	element at the end of insn_conditions.
	(write_writer): Use ARRAY_SIZE (insn_conditions) - 1 instead of
	ARRAY_SIZE (insn_conditions).

diff --git a/gcc/genconditions.cc b/gcc/genconditions.cc
index 202813d..f63a3f4 100644 (file)
--- a/gcc/genconditions.cc
+++ b/gcc/genconditions.cc
@@ -175,7 +175,7 @@ static const struct c_test insn_conditions[] = {\n");
 
   traverse_c_tests (write_one_condition, 0);
 
-  puts ("\n};\n#endif /* gcc >= 3.0.1 */\n");
+  puts ("  { nullptr, -1 }\n};\n#endif /* gcc >= 3.0.1 */\n");
 }
 
 /* Emit code which will convert the C-format table to a
@@ -192,7 +192,7 @@ write_writer (void)
         "  const char *p;\n"
         "  puts (\"(define_conditions [\");\n"
        "#if GCC_VERSION >= 3001\n"
-       "  for (i = 0; i < ARRAY_SIZE (insn_conditions); i++)\n"
+       "  for (i = 0; i < ARRAY_SIZE (insn_conditions) - 1; i++)\n"
        "    {\n"
        "      printf (\"  (%d \\\"\", insn_conditions[i].value);\n"
        "      for (p = insn_conditions[i].expr; *p; p++)\n"