RISC-V: Refer mapping symbol to R_RISCV_RELAX for rvc relaxations.

RISC-V Psabi pr116,
riscv-non-isa/riscv-elf-psabi-doc#116

bfd/
    * elfnn-riscv.c (_bfd_riscv_enable_rvc): New function to check the
    mapping symbol with architecture string in the R_RISCV_RELAX, to see
    if rvc is enabled or not.  If we don't find any mapping symbols, then
    just check the elf header flag as usual.
    (_bfd_riscv_relax_call): Updated since above change.
    (_bfd_riscv_relax_lui): Likewise.
gas/
    * config/tc-riscv.c (append_insn): Store $x+arch in tc_fix_data if exsit.
    (md_apply_fix): Refer the $x+arch from tc_fix_data into R_RISCV_RELAX,
    these only for the relocations used to do rvc relaxation.  Besides, set
    addend of R_RISCV_RELAX (fx_offset) to zero.
    * config/tc-riscv.h (TC_FIX_TYPE): Defined to store $x+arch in each fixup
    only for risc-v target.
    (struct riscv_fixup_type): Likewise.
    (TC_INIT_FIX_DATA): Likewise.
    * testsuite/gas/riscv/mapping-relax.d: New testcase.
    * testsuite/gas/riscv/mapping-relax.s: Likewise.
ld/
    * testsuite/ld-riscv-elf/c-relax.d: New testcase for specific rvc relaxation.
    * testsuite/ld-riscv-elf/c-relax.s: Likewise.
    * testsuite/ld-riscv-elf/ld-riscv-elf.exp: Updated.

bfd/elfnn-riscv.c

@@ -4168,6 +4168,31 @@ typedef bool (*relax_func_t) (bfd *, asection *, asection *,
 			      riscv_pcgp_relocs *,
 			      bool undefined_weak);
 
+/* Check the mapping symbol with architecture string in the R_RISCV_RELAX,
+   to see if rvc is enabled or not.  If we don't find any mapping symbols,
+   then just check the elf header flag as usual.  */
+
+static int
+_bfd_riscv_enable_rvc (bfd *abfd, Elf_Internal_Rela *rel)
+{
+  Elf_Internal_Shdr *symtab_hdr = &elf_symtab_hdr (abfd);
+  int rvc = elf_elfheader (abfd)->e_flags & EF_RISCV_RVC;
+  if (ELFNN_R_SYM (rel->r_info) < symtab_hdr->sh_info)
+    {
+      Elf_Internal_Sym *isym = ((Elf_Internal_Sym *) symtab_hdr->contents
+				+ ELFNN_R_SYM (rel->r_info));
+
+      if (isym->st_shndx == SHN_UNDEF
+	  || isym->st_shndx >= elf_numsections (abfd))
+	return rvc;
+
+      const char *name = bfd_elf_sym_name (abfd, symtab_hdr, isym, NULL);
+      rvc = (name && strncmp (name, "$xrv", 4) == 0
+	     && strstr (name, "_c") != NULL) ? 1 : 0;
+    }
+  return rvc;
+}
+
 /* Relax AUIPC + JALR into JAL.  */
 
 static bool
@@ -4185,7 +4210,8 @@ _bfd_riscv_relax_call (bfd *abfd, asection *sec, asection *sym_sec,
   bfd_vma foff = symval - (sec_addr (sec) + rel->r_offset);
   bool near_zero = (symval + RISCV_IMM_REACH / 2) < RISCV_IMM_REACH;
   bfd_vma auipc, jalr;
-  int rd, r_type, len = 4, rvc = elf_elfheader (abfd)->e_flags & EF_RISCV_RVC;
+  int rd, r_type, len = 4;
+  int rvc = _bfd_riscv_enable_rvc (abfd, rel + 1);
 
   /* If the call crosses section boundaries, an alignment directive could
      cause the PC-relative offset to later increase, so we need to add in the
@@ -4279,7 +4305,6 @@ _bfd_riscv_relax_lui (bfd *abfd,
 {
   bfd_byte *contents = elf_section_data (sec)->this_hdr.contents;
   bfd_vma gp = riscv_global_pointer_value (link_info);
-  int use_rvc = elf_elfheader (abfd)->e_flags & EF_RISCV_RVC;
 
   BFD_ASSERT (rel->r_offset + 4 <= sec->size);
 
@@ -4347,7 +4372,7 @@ _bfd_riscv_relax_lui (bfd *abfd,
      account for this assuming page alignment at worst. In the presence of 
      RELRO segment the linker aligns it by one page size, therefore sections
      after the segment can be moved more than one page. */
-
+  int use_rvc = _bfd_riscv_enable_rvc (abfd, rel + 1);
   if (use_rvc
       && ELFNN_R_TYPE (rel->r_info) == R_RISCV_HI20
       && VALID_CITYPE_LUI_IMM (RISCV_CONST_HIGH_PART (symval))

gas/config/tc-riscv.c

@@ -511,7 +511,8 @@ make_mapping_symbol (enum riscv_seg_mstate state,
   symbol_get_bfdsym (symbol)->flags |= (BSF_NO_FLAGS | BSF_LOCAL);
   if (reset_seg_arch_str)
     {
-      /* Store current $x+arch into tc_segment_info.  */
+      /* Store current $x+arch into tc_segment_info, so that we can
+	 refer to the correct $x+arch for each R_RISCV_RELAX.  */
       seg_info (now_seg)->tc_segment_info_data.arch_map_symbol = symbol;
       xfree ((void *) buff);
     }
@@ -1558,6 +1559,8 @@ append_insn (struct riscv_cl_insn *ip, expressionS *address_expr,
 				  address_expr, false, reloc_type);
 
 	  ip->fixp->fx_tcbit = riscv_opts.relax;
+	  ip->fixp->tc_fix_data.arch_map_symbol =
+		seg_info (now_seg)->tc_segment_info_data.arch_map_symbol;
 	}
     }
 
@@ -3731,6 +3734,7 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg ATTRIBUTE_UNUSED)
   unsigned int subtype;
   bfd_byte *buf = (bfd_byte *) (fixP->fx_frag->fr_literal + fixP->fx_where);
   bool relaxable = false;
+  bool rvc_relaxable = false;
   offsetT loc;
   segT sub_segment;
 
@@ -3747,6 +3751,7 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg ATTRIBUTE_UNUSED)
       if (fixP->fx_addsy == NULL)
 	fixP->fx_done = true;
       relaxable = true;
+      rvc_relaxable = true;
       break;
 
     case BFD_RELOC_RISCV_GOT_HI20:
@@ -3940,6 +3945,7 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg ATTRIBUTE_UNUSED)
     case BFD_RELOC_RISCV_CALL:
     case BFD_RELOC_RISCV_CALL_PLT:
       relaxable = true;
+      rvc_relaxable = true;
       break;
 
     case BFD_RELOC_RISCV_PCREL_HI20:
@@ -3964,9 +3970,14 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg ATTRIBUTE_UNUSED)
   if (relaxable && fixP->fx_tcbit && fixP->fx_addsy != NULL)
     {
       fixP->fx_next = xmemdup (fixP, sizeof (*fixP), sizeof (*fixP));
-      fixP->fx_next->fx_addsy = fixP->fx_next->fx_subsy = NULL;
+      /* Currently only rvc relaxations need $x+arch.  */
+      fixP->fx_next->fx_addsy = (need_arch_map_symbol && rvc_relaxable)
+				? fixP->tc_fix_data.arch_map_symbol : NULL;
+      fixP->fx_next->fx_subsy = NULL;
       fixP->fx_next->fx_r_type = BFD_RELOC_RISCV_RELAX;
       fixP->fx_next->fx_size = 0;
+      /* Set addend to zero.  */
+      fixP->fx_next->fx_offset = 0;
     }
 }
 

gas/config/tc-riscv.h

@@ -152,6 +152,13 @@ struct riscv_frag_type
 #define TC_FRAG_INIT(fragp, max_bytes) riscv_init_frag (fragp, max_bytes)
 extern void riscv_init_frag (struct frag *, int);
 
+#define TC_FIX_TYPE struct riscv_fixup_type
+struct riscv_fixup_type
+{
+  symbolS *arch_map_symbol;
+};
+#define TC_INIT_FIX_DATA(FIX) ((FIX)->tc_fix_data.arch_map_symbol = NULL)
+
 #define obj_adjust_symtab() riscv_adjust_symtab ()
 extern void riscv_adjust_symtab (void);
 

gas/testsuite/gas/riscv/mapping-relax.d

@@ -0,0 +1,23 @@
+#name:
+#source: mapping-relax.s
+#as:
+#readelf: -rW
+
+Relocation section '.rela.text' at .*
+[ ]+Offset[ ]+Info[ ]+Type[ ]+.*
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_HI20[ 	]+[0-9a-f]+[ 	]+foo \+ 0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_RELAX[ 	]+[0-9a-f]+[ 	]+\$xrv32i2p1 \+ 0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_LO12_I[ 	]+[0-9a-f]+[ 	]+foo \+ 4
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_RELAX[ 	]+[0-9a-f]+[ 	]+\$xrv32i2p1 \+ 0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_TPREL_HI20[ 	]+[0-9a-f]+[ 	]+i \+ 0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_RELAX[ 	]+0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_TPREL_ADD[ 	]+[0-9a-f]+[ 	]+i \+ 0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_RELAX[ 	]+0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_TPREL_LO12_I[ 	]+[0-9a-f]+[ 	]+i \+ 0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_RELAX[ 	]+0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_PCREL_HI20[ 	]+[0-9a-f]+[ 	]+foo \+ 0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_RELAX[ 	]+0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_PCREL_LO12_I[ 	]+[0-9a-f]+[ 	]+L1 \+ 0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_RELAX[ 	]+0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_CALL_PLT[ 	]+[0-9a-f]+[ 	]+foo \+ 0
+[0-9a-f]+[ 	]+[0-9a-f]+[ 	]+R_RISCV_RELAX[ 	]+[0-9a-f]+[ 	]+\$xrv32i2p1_c2p0 \+ 0

gas/testsuite/gas/riscv/mapping-relax.s

@@ -0,0 +1,21 @@
+.attribute arch, "rv32i"
+.option relax
+foo:
+.align	2
+lui	a0, %hi (foo)
+addi	a0, a0, %lo (foo + 4)
+.option arch, +a
+lui	a0, %tprel_hi (i)
+add	a0, a0, tp, %tprel_add (i)
+lw	a1, %tprel_lo (i) (a0)
+.option arch, -a, +c
+L1: auipc	a0, %pcrel_hi (foo)
+addi	a0, a0, %pcrel_lo (L1)
+call	foo
+
+.globl	i
+.section .tbss, "awT", @nobits
+.type	i, @object
+.size	i, 4
+i:
+.zero	4

ld/testsuite/ld-riscv-elf/c-relax.d

@@ -0,0 +1,16 @@
+#source: c-relax.s
+#ld: --relax
+#objdump: -d -Mno-aliases
+
+.*:[ 	]+file format .*
+
+
+Disassembly of section .text:
+
+0+[0-9a-f]+ <_start>:
+.*:[ 	]+[0-9a-f]+[ 	]+lui[ 	]+.*
+.*:[ 	]+[0-9a-f]+[ 	]+addi[ 	]+.*
+.*:[ 	]+[0-9a-f]+[ 	]+c\.lui[ 	]+.*
+.*:[ 	]+[0-9a-f]+[ 	]+addi[ 	]+.*
+.*:[ 	]+[0-9a-f]+[ 	]+c\.j[ 	]+.*
+.*:[ 	]+[0-9a-f]+[ 	]+jal[ 	]+.*

ld/testsuite/ld-riscv-elf/c-relax.s

@@ -0,0 +1,12 @@
+.option relax
+.option arch, -c
+.globl _start
+_start:
+lui	a0, %hi (_start)
+addi	a0, a0, %lo (_start)
+.option arch, +c
+lui	a0, %hi (_start)
+addi	a0, a0, %lo (_start)
+call	zero, _start
+.option arch, -c
+call	zero, _start

ld/testsuite/ld-riscv-elf/ld-riscv-elf.exp

@@ -125,6 +125,7 @@ if [istarget "riscv*-*-*"] {
     run_dump_test "pcgp-relax-02"
     run_dump_test "c-lui"
     run_dump_test "c-lui-2"
+    run_dump_test "c-relax"
     run_dump_test "disas-jalr"
     run_dump_test "pcrel-lo-addend"
     run_dump_test "pcrel-lo-addend-2a"