RFA: Improve message for wrong number of alternatives

[Joern Rennecke]

When you have lots of operands and lots of alternatives in a pattern,
it is often not immediately apparent if the problem is in the
indicated alternative or in the one that genoutput uses as a reference
for the 'correct' number of alternatives, and/or if you dropped a
comma or had one too many.  By making genoutput tell you what the
argument counts are, this gets a little bit easier.

Bootstrapped on x86_64-pc-linux-gnu.

2021-01-13  Joern Rennecke  <joern.renne...@embecosm.com>

        Make "wrong number of alternatives" message a bit more specific.

diff --git a/gcc/genoutput.c b/gcc/genoutput.c
index 8e911cce2f5..d2836f85bbf 100644
--- a/gcc/genoutput.c
+++ b/gcc/genoutput.c
@@ -813,8 +813,8 @@ validate_insn_alternatives (class data *d)
            if (n == 0)
              n = d->operand[start].n_alternatives;
            else if (n != d->operand[start].n_alternatives)
-             error_at (d->loc, "wrong number of alternatives in operand %d",
-                       start);
+             error_at (d->loc, "wrong number of alternatives in operand %d, 
%d, expected %d",
+                       start, d->operand[start].n_alternatives, n);
          }
       }