except: Fix __builtin_eh_return_data_regno (-42) expansion [PR101195]

The expansion of this builtin emits an error if the argument is not
INTEGER_CST, otherwise uses tree_to_uhwi on the argument (which is declared
int) and then uses EH_RETURN_DATA_REGNO macro which on most targets returns
INVALID_REGNUM for all values but some small number (2 or 4); if it returns
INVALID_REGNUM, we silently expand to -1.

Now, I think the error for non-INTEGER_CST makes sense to catch when people
unintentionally don't call it with a constant (but, users shouldn't really
use this builtin anyway, it is for the unwinder only).  Initially I thought
about emitting an error for the negative values as well on which
tree_to_uhwi otherwise ICEs, but given that the function will silently
expand to -1 for INT_MAX - 1 or INT_MAX - 3 other values, I think treating
the negatives the same silently is fine too.

2024-01-30  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/101195
	* except.cc (expand_builtin_eh_return_data_regno): If which doesn't
	fit into unsigned HOST_WIDE_INT, return constm1_rtx.

	* gcc.dg/pr101195.c: New test.

gcc/except.cc

@@ -2167,6 +2167,9 @@ expand_builtin_eh_return_data_regno (tree exp)
       return constm1_rtx;
     }
 
+  if (!tree_fits_uhwi_p (which))
+    return constm1_rtx;
+
   iwhich = tree_to_uhwi (which);
   iwhich = EH_RETURN_DATA_REGNO (iwhich);
   if (iwhich == INVALID_REGNUM)

gcc/testsuite/gcc.dg/pr101195.c

@@ -0,0 +1,8 @@
+/* PR middle-end/101195 */
+/* { dg-do compile } */
+
+int
+foo (void)
+{
+  return __builtin_eh_return_data_regno (-42);
+}