LoongArch: Add enum-style -mexplicit-relocs= option

To take a better balance between scheduling and relaxation when -flto is
enabled, add three-way -mexplicit-relocs={auto,none,always} options.
The old -mexplicit-relocs and -mno-explicit-relocs options are still
supported, they are mapped to -mexplicit-relocs=always and
-mexplicit-relocs=none.

The default choice is determined by probing assembler capabilities at
build time.  If the assembler does not supports explicit relocs at all,
the default will be none; if it supports explicit relocs but not
relaxation, the default will be always; if both explicit relocs and
relaxation are supported, the default will be auto.

Currently auto is same as none.  We will make auto more clever in
following changes.

gcc/ChangeLog:

	* config/loongarch/genopts/loongarch-strings: Add strings for
	-mexplicit-relocs={auto,none,always}.
	* config/loongarch/genopts/loongarch.opt.in: Add options for
	-mexplicit-relocs={auto,none,always}.
	* config/loongarch/loongarch-str.h: Regenerate.
	* config/loongarch/loongarch.opt: Regenerate.
	* config/loongarch/loongarch-def.h
	(EXPLICIT_RELOCS_AUTO): Define.
	(EXPLICIT_RELOCS_NONE): Define.
	(EXPLICIT_RELOCS_ALWAYS): Define.
	(N_EXPLICIT_RELOCS_TYPES): Define.
	* config/loongarch/loongarch.cc
	(loongarch_option_override_internal): Error out if the old-style
	-m[no-]explicit-relocs option is used with
	-mexplicit-relocs={auto,none,always} together.  Map
	-mno-explicit-relocs to -mexplicit-relocs=none and
	-mexplicit-relocs to -mexplicit-relocs=always for backward
	compatibility.  Set a proper default for -mexplicit-relocs=
	based on configure-time probed linker capability.  Update a
	diagnostic message to mention -mexplicit-relocs=always instead
	of the old-style -mexplicit-relocs.
	(loongarch_handle_model_attribute): Update a diagnostic message
	to mention -mexplicit-relocs=always instead of the old-style
	-mexplicit-relocs.
	* config/loongarch/loongarch.h (TARGET_EXPLICIT_RELOCS): Define.

gcc/config/loongarch/genopts/loongarch-strings

@@ -63,3 +63,9 @@ STR_CMODEL_TS	      tiny-static
 STR_CMODEL_MEDIUM     medium
 STR_CMODEL_LARGE      large
 STR_CMODEL_EXTREME    extreme
+
+# -mexplicit-relocs
+OPTSTR_EXPLICIT_RELOCS		explicit-relocs
+STR_EXPLICIT_RELOCS_AUTO	auto
+STR_EXPLICIT_RELOCS_NONE	none
+STR_EXPLICIT_RELOCS_ALWAYS	always

gcc/config/loongarch/genopts/loongarch.opt.in

@@ -170,10 +170,27 @@ mmax-inline-memcpy-size=
 Target Joined RejectNegative UInteger Var(loongarch_max_inline_memcpy_size) Init(1024)
 -mmax-inline-memcpy-size=SIZE	Set the max size of memcpy to inline, default is 1024.
 
-mexplicit-relocs
-Target Var(TARGET_EXPLICIT_RELOCS) Init(HAVE_AS_EXPLICIT_RELOCS & !HAVE_AS_MRELAX_OPTION)
+Enum
+Name(explicit_relocs) Type(int)
+The code model option names for -mexplicit-relocs:
+
+EnumValue
+Enum(explicit_relocs) String(@@STR_EXPLICIT_RELOCS_AUTO@@) Value(EXPLICIT_RELOCS_AUTO)
+
+EnumValue
+Enum(explicit_relocs) String(@@STR_EXPLICIT_RELOCS_NONE@@) Value(EXPLICIT_RELOCS_NONE)
+
+EnumValue
+Enum(explicit_relocs) String(@@STR_EXPLICIT_RELOCS_ALWAYS@@) Value(EXPLICIT_RELOCS_ALWAYS)
+
+mexplicit-relocs=
+Target RejectNegative Joined Enum(explicit_relocs) Var(la_opt_explicit_relocs) Init(M_OPT_UNSET)
 Use %reloc() assembly operators.
 
+mexplicit-relocs
+Target Var(la_opt_explicit_relocs_backward) Init(M_OPT_UNSET)
+Use %reloc() assembly operators (for backward compatibility).
+
 ; The code model option names for -mcmodel.
 Enum
 Name(cmodel) Type(int)

gcc/config/loongarch/loongarch-def.h

@@ -99,6 +99,12 @@ extern const char* loongarch_cmodel_strings[];
 #define CMODEL_EXTREME	      5
 #define N_CMODEL_TYPES	      6
 
+/* enum explicit_relocs */
+#define EXPLICIT_RELOCS_AUTO	0
+#define EXPLICIT_RELOCS_NONE	1
+#define EXPLICIT_RELOCS_ALWAYS	2
+#define N_EXPLICIT_RELOCS_TYPES	3
+
 /* The common default value for variables whose assignments
    are triggered by command-line options.  */
 

gcc/config/loongarch/loongarch-str.h

@@ -62,4 +62,9 @@ along with GCC; see the file COPYING3.  If not see
 #define STR_CMODEL_LARGE "large"
 #define STR_CMODEL_EXTREME "extreme"
 
+#define OPTSTR_EXPLICIT_RELOCS "explicit-relocs"
+#define STR_EXPLICIT_RELOCS_AUTO "auto"
+#define STR_EXPLICIT_RELOCS_NONE "none"
+#define STR_EXPLICIT_RELOCS_ALWAYS "always"
+
 #endif /* LOONGARCH_STR_H */

gcc/config/loongarch/loongarch.cc

@@ -7387,6 +7387,25 @@ loongarch_option_override_internal (struct gcc_options *opts,
   loongarch_update_gcc_opt_status (&la_target, opts, opts_set);
   loongarch_cpu_option_override (&la_target, opts, opts_set);
 
+  if (la_opt_explicit_relocs != M_OPT_UNSET
+      && la_opt_explicit_relocs_backward != M_OPT_UNSET)
+    error ("do not use %qs (with %qs) and %qs (without %qs) together",
+	   "-mexplicit-relocs=", "=",
+	   la_opt_explicit_relocs_backward ? "-mexplicit-relocs"
+					   : "-mno-explicit-relocs", "=");
+
+  if (la_opt_explicit_relocs_backward != M_OPT_UNSET)
+    la_opt_explicit_relocs = (la_opt_explicit_relocs_backward
+			      ? EXPLICIT_RELOCS_ALWAYS
+			      : EXPLICIT_RELOCS_NONE);
+
+  if (la_opt_explicit_relocs == M_OPT_UNSET)
+    la_opt_explicit_relocs = (HAVE_AS_EXPLICIT_RELOCS
+			      ? (HAVE_AS_MRELAX_OPTION
+				 ? EXPLICIT_RELOCS_AUTO
+				 : EXPLICIT_RELOCS_ALWAYS)
+			      : EXPLICIT_RELOCS_NONE);
+
   if (TARGET_ABI_LP64)
     flag_pcc_struct_return = 0;
 
@@ -7417,7 +7436,7 @@ loongarch_option_override_internal (struct gcc_options *opts,
       case CMODEL_EXTREME:
 	if (!TARGET_EXPLICIT_RELOCS)
 	  error ("code model %qs needs %s",
-		 "extreme", "-mexplicit-relocs");
+		 "extreme", "-mexplicit-relocs=always");
 
 	if (opts->x_flag_plt)
 	  {
@@ -7721,7 +7740,8 @@ loongarch_handle_model_attribute (tree *node, tree name, tree arg, int,
       if (!TARGET_EXPLICIT_RELOCS)
 	{
 	  error_at (DECL_SOURCE_LOCATION (decl),
-		    "%qE attribute requires %s", name, "-mexplicit-relocs");
+		    "%qE attribute requires %s", name,
+		    "-mexplicit-relocs=always");
 	  *no_add_attrs = true;
 	  return NULL_TREE;
 	}

gcc/config/loongarch/loongarch.h

@@ -1236,3 +1236,6 @@ struct GTY (()) machine_function
    we just need "ibar" to avoid instruction hazard here.  */
 #undef  CLEAR_INSN_CACHE
 #define CLEAR_INSN_CACHE(beg, end) __builtin_loongarch_ibar (0)
+
+#define TARGET_EXPLICIT_RELOCS \
+  (la_opt_explicit_relocs == EXPLICIT_RELOCS_ALWAYS)

gcc/config/loongarch/loongarch.opt

@@ -177,10 +177,27 @@ mmax-inline-memcpy-size=
 Target Joined RejectNegative UInteger Var(loongarch_max_inline_memcpy_size) Init(1024)
 -mmax-inline-memcpy-size=SIZE	Set the max size of memcpy to inline, default is 1024.
 
-mexplicit-relocs
-Target Var(TARGET_EXPLICIT_RELOCS) Init(HAVE_AS_EXPLICIT_RELOCS & !HAVE_AS_MRELAX_OPTION)
+Enum
+Name(explicit_relocs) Type(int)
+The code model option names for -mexplicit-relocs:
+
+EnumValue
+Enum(explicit_relocs) String(auto) Value(EXPLICIT_RELOCS_AUTO)
+
+EnumValue
+Enum(explicit_relocs) String(none) Value(EXPLICIT_RELOCS_NONE)
+
+EnumValue
+Enum(explicit_relocs) String(always) Value(EXPLICIT_RELOCS_ALWAYS)
+
+mexplicit-relocs=
+Target RejectNegative Joined Enum(explicit_relocs) Var(la_opt_explicit_relocs) Init(M_OPT_UNSET)
 Use %reloc() assembly operators.
 
+mexplicit-relocs
+Target Var(la_opt_explicit_relocs_backward) Init(M_OPT_UNSET)
+Use %reloc() assembly operators (for backward compatibility).
+
 ; The code model option names for -mcmodel.
 Enum
 Name(cmodel) Type(int)