as: add option for generate R_LARCH_32/64_PCREL.

Some older kernels cannot handle the newly generated R_LARCH_32/64_PCREL,
so the assembler generates R_LARCH_ADD32/64+R_LARCH_SUB32/64 by default,
and use the assembler option mthin-add-sub to generate R_LARCH_32/64_PCREL
as much as possible.

The Option of mthin-add-sub does not affect the generation of R_LARCH_32_PCREL
relocation in .eh_frame.

gas/config/tc-loongarch.c

@@ -120,6 +120,7 @@ enum options
   OPTION_LA_GLOBAL_WITH_ABS,
   OPTION_RELAX,
   OPTION_NO_RELAX,
+  OPTION_THIN_ADD_SUB,
 
   OPTION_END_OF_ENUM,
 };
@@ -136,6 +137,7 @@ struct option md_longopts[] =
 
   { "mrelax", no_argument, NULL, OPTION_RELAX },
   { "mno-relax", no_argument, NULL, OPTION_NO_RELAX },
+  { "mthin-add-sub", no_argument, NULL, OPTION_THIN_ADD_SUB},
 
   { NULL, no_argument, NULL, 0 }
 };
@@ -214,6 +216,10 @@ md_parse_option (int c, const char *arg)
       LARCH_opts.relax = 0;
       break;
 
+    case OPTION_THIN_ADD_SUB:
+      LARCH_opts.thin_add_sub = 1;
+      break;
+
     case OPTION_IGNORE:
       break;
 
@@ -1195,6 +1201,7 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg ATTRIBUTE_UNUSED)
   static int64_t stack_top;
   static int last_reloc_is_sop_push_pcrel_1 = 0;
   int last_reloc_is_sop_push_pcrel = last_reloc_is_sop_push_pcrel_1;
+  segT sub_segment;
   last_reloc_is_sop_push_pcrel_1 = 0;
 
   char *buf = fixP->fx_frag->fr_literal + fixP->fx_where;
@@ -1287,6 +1294,23 @@ md_apply_fix (fixS *fixP, valueT *valP, segT seg ATTRIBUTE_UNUSED)
 	    }
 	}
 
+      /* If symbol in .eh_frame the address may be adjusted, and contents of
+	 .eh_frame will be adjusted, so use pc-relative relocation for FDE
+	 initial location.
+	 The Option of mthin-add-sub does not affect the generation of
+	 R_LARCH_32_PCREL relocation in .eh_frame.  */
+      if (fixP->fx_r_type == BFD_RELOC_32
+	  && fixP->fx_addsy && fixP->fx_subsy
+	  && (sub_segment = S_GET_SEGMENT (fixP->fx_subsy))
+	  && strcmp (sub_segment->name, ".eh_frame") == 0
+	  && S_GET_VALUE (fixP->fx_subsy)
+	  == fixP->fx_frag->fr_address + fixP->fx_where)
+	{
+	  fixP->fx_r_type = BFD_RELOC_LARCH_32_PCREL;
+	  fixP->fx_subsy = NULL;
+	  break;
+	}
+
       if (fixP->fx_addsy && fixP->fx_subsy)
 	{
 	  fixP->fx_next = xmemdup (fixP, sizeof (*fixP), sizeof (*fixP));
@@ -1589,6 +1613,11 @@ md_show_usage (FILE *stream)
 {
   fprintf (stream, _("LARCH options:\n"));
   /* FIXME */
+  fprintf (stream, _("\
+  -mthin-add-sub	  Convert a pair of R_LARCH_ADD32/64 and R_LARCH_SUB32/64 to\n\
+			  R_LARCH_32/64_PCREL as much as possible\n\
+			  The option does not affect the generation of R_LARCH_32_PCREL\n\
+			  relocations in .eh_frame\n"));
 }
 
 static void

gas/config/tc-loongarch.h

@@ -75,12 +75,13 @@ extern bool loongarch_frag_align_code (int);
    or PC at start of subsy or with relax but sub_symbol_segment not in
    SEC_CODE, we generate 32/64_PCREL.  */
 #define TC_FORCE_RELOCATION_SUB_LOCAL(FIX, SEG) \
-  (!((BFD_RELOC_32 || BFD_RELOC_64) \
-     &&(!LARCH_opts.relax \
-       || S_GET_VALUE (FIX->fx_subsy) \
-	  == FIX->fx_frag->fr_address + FIX->fx_where \
-       || (LARCH_opts.relax \
-	  && ((S_GET_SEGMENT (FIX->fx_subsy)->flags & SEC_CODE) == 0)))))
+  (!(LARCH_opts.thin_add_sub \
+     && (BFD_RELOC_32 || BFD_RELOC_64) \
+     && (!LARCH_opts.relax \
+	|| S_GET_VALUE (FIX->fx_subsy) \
+	   == FIX->fx_frag->fr_address + FIX->fx_where \
+	|| (LARCH_opts.relax \
+	   && ((S_GET_SEGMENT (FIX->fx_subsy)->flags & SEC_CODE) == 0)))))
 
 #define TC_VALIDATE_FIX_SUB(FIX, SEG) 1
 #define DIFF_EXPR_OK 1

include/opcode/loongarch.h

@@ -236,6 +236,7 @@ dec2 : [1-9][0-9]?
 #define ase_gabs	isa.use_la_global_with_abs
 
     int relax;
+    int thin_add_sub;
   } LARCH_opts;
 
   extern size_t loongarch_insn_length (insn_t insn);