RISC-V: Add --[no-]relax-gp to ld

--relax enables all relaxations.  --no-relax-gp disables GP relaxation to
allow measuring its effect.

The option can test effectiveness of GP relaxation and support some ABI
variants that use GP for other purposes.

Link: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/issues/298

bfd/
    * elfnn-riscv.c (struct riscv_elf_link_hash_table): Add params.
    (riscv_elfNN_set_options): New.
    (riscv_info_to_howto_rela): Check relax_gp.
    (_bfd_riscv_relax_section): Likewise.
    * elfxx-riscv.h (struct riscv_elf_params): New.
    (riscv_elf32_set_options): New.
    (riscv_elf64_set_options): New.
ld/
    * emultempl/riscvelf.em: Add option parsing.
    * testsuite/ld-riscv-elf/code-model-relax-medlow-01-norelaxgp.d: New.
    * testsuite/ld-riscv-elf/pcgp-relax-01-norelaxgp.d: New.
    * testsuite/ld-riscv-elf/pcgp-relax-02.d: Test --relax --relax-gp can be
      used together.

1 files changed, 36 insertions, 0 deletions

diff --git a/ld/emultempl/riscvelf.em b/ld/emultempl/riscvelf.em
index b12d150..bb6298d 100644
--- a/ld/emultempl/riscvelf.em
+++ b/ld/emultempl/riscvelf.em
@@ -25,6 +25,40 @@ fragment <<EOF
 #include "elf/riscv.h"
 #include "elfxx-riscv.h"
 
+static struct riscv_elf_params params = { .relax_gp = 1 };
+EOF
+
+# Define some shell vars to insert bits of code into the standard elf
+# parse_args and list_options functions.  */
+PARSE_AND_LIST_PROLOGUE=${PARSE_AND_LIST_PROLOGUE}'
+enum risccv_opt
+{
+  OPTION_RELAX_GP = 321,
+  OPTION_NO_RELAX_GP,
+};
+'
+
+PARSE_AND_LIST_LONGOPTS=${PARSE_AND_LIST_LONGOPTS}'
+    { "relax-gp", no_argument, NULL, OPTION_RELAX_GP },
+    { "no-relax-gp", no_argument, NULL, OPTION_NO_RELAX_GP },
+'
+
+PARSE_AND_LIST_OPTIONS=${PARSE_AND_LIST_OPTIONS}'
+  fprintf (file, _("  --relax-gp                  Perform GP relaxation\n"));
+  fprintf (file, _("  --no-relax-gp               Don'\''t perform GP relaxation\n"));
+'
+
+PARSE_AND_LIST_ARGS_CASES=${PARSE_AND_LIST_ARGS_CASES}'
+    case OPTION_RELAX_GP:
+      params.relax_gp = 1;
+      break;
+
+    case OPTION_NO_RELAX_GP:
+      params.relax_gp = 0;
+      break;
+'
+
+fragment <<EOF
 static void
 riscv_elf_before_allocation (void)
 {
@@ -96,6 +130,8 @@ riscv_create_output_section_statements (void)
 	       " whilst linking %s binaries\n"), "RISC-V");
       return;
     }
+
+  riscv_elf${ELFSIZE}_set_options (&link_info, &params);
 }
 
 EOF