[PATCH] Fix print_multilib_info when default arguments appear in the option list with '!'

[Kito Cheng]

This issue is found when we try to always define MULTILIB_DEFAULTS for -march
and -mabi for RISC-V back-end, however `-print-multi-lib` will skip
multi-lib setting if match any one of flag in MULTILIB_DEFAULTS, even
some options are specified in the option list with '!'.

e.g.

We have default march=rv32i and mabi=ilp32.

And we have following multi-lib set:

". !march=rv32i !march=rv32im !march=rv32imafc !mabi=ilp32 !mabi=ilp32f;"
"rv32i/ilp32 march=rv32i !march=rv32im !march=rv32imafc mabi=ilp32 
!mabi=ilp32f;"
"rv32im/ilp32 !march=rv32i march=rv32im !march=rv32imafc mabi=ilp32 
!mabi=ilp32f;"
"rv32imafc/ilp32f !march=rv32i !march=rv32ic !march=rv32im march=rv32imafc 
!mabi=ilp32 mabi=ilp32f;"

`-print-multi-lib` willl show `.` and `rv32imafc/ilp32f` only, because
the mabi=ilp32 is matched, however there is `!march=rv32i` in `rv32im/ilp32`, so
`rv32im/ilp32` should keep, because it reject march=rv32i.

Note: This can be reproduced via following configure options with patch [1]:
gcc/configure --target=riscv64-elf --with-arch=rv32i --with-abi=ilp32 \
  --with-multilib-generator="rv32i-ilp32--;rv32im-ilp32--;rv32imafc-ilp32f--"

[1] https://gcc.gnu.org/pipermail/gcc-patches/2020-November/559707.html

gcc/ChangeLog:

        * gcc.c (print_multilib_info): Check default arguments not
        appeared in multi-lib option list with '!'
---
 gcc/gcc.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/gcc/gcc.c b/gcc/gcc.c
index 26bc5065eeb..b2a26b5af81 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -9730,6 +9730,7 @@ print_multilib_info (void)
   const char *p = multilib_select;
   const char *last_path = 0, *this_path;
   int skip;
+  int not_arg;
   unsigned int last_path_len = 0;
 
   while (*p != '\0')
@@ -9884,9 +9885,13 @@ print_multilib_info (void)
                goto invalid_select;
 
              if (*q == '!')
-               arg = NULL;
+               {
+                 not_arg = 1;
+                 q++;
+               }
              else
-               arg = q;
+               not_arg = 0;
+             arg = q;
 
              while (*q != ' ' && *q != ';')
                {
@@ -9895,11 +9900,17 @@ print_multilib_info (void)
                  ++q;
                }
 
-             if (arg != NULL
-                 && default_arg (arg, q - arg))
+             if (default_arg (arg, q - arg))
                {
-                 skip = 1;
-                 break;
+                 /* Stop checking if any default arguments appeared in not
+                    list.  */
+                 if (not_arg)
+                   {
+                     skip = 0;
+                     break;
+                   }
+                 else
+                   skip = 1;
                }
 
              if (*q == ' ')
-- 
2.29.2