[to-be-committed] RISC-V: Don't use structured binding in riscv-common.cc

[Kito Cheng]

It's new C++ language feature introduced in C++17, which is higher than
the build environment required by the GCC (C++14).

gcc/ChangeLog:

        * common/config/riscv/riscv-common.cc: Remove structured binding
        from the code.
---
 gcc/common/config/riscv/riscv-common.cc | 27 ++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/gcc/common/config/riscv/riscv-common.cc 
b/gcc/common/config/riscv/riscv-common.cc
index a6d8763f032..6b5440365e3 100644
--- a/gcc/common/config/riscv/riscv-common.cc
+++ b/gcc/common/config/riscv/riscv-common.cc
@@ -1129,8 +1129,10 @@ riscv_subset_list::check_implied_ext ()
 void
 riscv_subset_list::handle_combine_ext ()
 {
-  for (const auto &[ext_name, ext_info] : riscv_ext_infos)
+  for (const auto &pair : riscv_ext_infos)
     {
+      const std::string &ext_name = pair.first;
+      auto &ext_info = pair.second;
       bool is_combined = true;
       /* Skip if this extension don't need to combine.  */
       if (!ext_info.need_combine_p ())
@@ -1558,20 +1560,27 @@ riscv_set_arch_by_subset_list (riscv_subset_list 
*subset_list,
   if (opts)
     {
       /* Clean up target flags before we set.  */
-      for (const auto &[ext_name, ext_info] : riscv_ext_infos)
-       ext_info.clean_opts (opts);
+      for (const auto &pair : riscv_ext_infos)
+       {
+         auto &ext_info = pair.second;
+         ext_info.clean_opts (opts);
+       }
 
       if (subset_list->xlen () == 32)
        opts->x_riscv_isa_flags &= ~MASK_64BIT;
       else if (subset_list->xlen () == 64)
        opts->x_riscv_isa_flags |= MASK_64BIT;
 
-      for (const auto &[ext_name, ext_info] : riscv_ext_infos)
-       if (subset_list->lookup (ext_name.c_str ()))
-         {
-           /* Set the extension flag.  */
-           ext_info.set_opts (opts);
-         }
+      for (const auto &pair : riscv_ext_infos)
+       {
+         const std::string &ext_name = pair.first;
+         auto &ext_info = pair.second;
+         if (subset_list->lookup (ext_name.c_str ()))
+           {
+             /* Set the extension flag.  */
+             ext_info.set_opts (opts);
+           }
+       }
     }
 }
 
-- 
2.34.1