LoongArch: Disable relaxation if the assembler don't support conditional branch relaxation [PR112330]

As the commit message of r14-4674 has indicated, if the assembler does
not support conditional branch relaxation, a relocation overflow may
happen on conditional branches when relaxation is enabled because the
number of NOP instructions inserted by the assembler will be more than
the number estimated by GCC.

To work around this issue, disable relaxation by default if the
assembler is detected incapable to perform conditional branch relaxation
at GCC build time.  We also need to pass -mno-relax to the assembler to
really disable relaxation.  But, if the assembler does not support
-mrelax option at all, we should not pass -mno-relax to the assembler or
it will immediately error out.  Also handle this with the build time
assembler capability probing, and add a pair of options
-m[no-]pass-mrelax-to-as to allow using a different assembler from the
build-time one.

With this change, if GCC is built with GAS 2.41, relaxation will be
disabled by default.  So the default value of -mexplicit-relocs= is also
changed to 'always' if -mno-relax is specified or implied by the
build-time default, because using assembler macros for symbol addresses
produces no benefit when relaxation is disabled.

gcc/ChangeLog:

	PR target/112330
	* config/loongarch/genopts/loongarch.opt.in: Add
	-m[no]-pass-relax-to-as.  Change the default of -m[no]-relax to
	account conditional branch relaxation support status.
	* config/loongarch/loongarch.opt: Regenerate.
	* configure.ac (gcc_cv_as_loongarch_cond_branch_relax): Check if
	the assembler supports conditional branch relaxation.
	* configure: Regenerate.
	* config.in: Regenerate.  Note that there are some unrelated
	changes introduced by r14-5424 (which does not contain a
	config.in regeneration).
	* config/loongarch/loongarch-opts.h
	(HAVE_AS_COND_BRANCH_RELAXATION): Define to 0 if not defined.
	* config/loongarch/loongarch-driver.h (ASM_MRELAX_DEFAULT):
	Define.
	(ASM_MRELAX_SPEC): Define.
	(ASM_SPEC): Use ASM_MRELAX_SPEC instead of "%{mno-relax}".
	* config/loongarch/loongarch.cc: Take the setting of
	-m[no-]relax into account when determining the default of
	-mexplicit-relocs=.
	* doc/invoke.texi: Document -m[no-]relax and
	-m[no-]pass-mrelax-to-as for LoongArch.  Update the default
	value of -mexplicit-relocs=.

9 files changed, 137 insertions, 13 deletions

diff --git a/gcc/config.in b/gcc/config.in
index 0509ba7..866f9ff 100644
--- a/gcc/config.in
+++ b/gcc/config.in
@@ -386,6 +386,12 @@
 #endif
 
 
+/* Define if your assembler supports conditional branch relaxation. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_AS_COND_BRANCH_RELAXATION
+#endif
+
+
 /* Define if your assembler supports the --debug-prefix-map option. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_AS_DEBUG_PREFIX_MAP
@@ -820,6 +826,20 @@
 #endif
 
 
+/* Define to 1 if you have the Mac OS X function
+   CFLocaleCopyPreferredLanguages in the CoreFoundation framework. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_CFLOCALECOPYPREFERREDLANGUAGES
+#endif
+
+
+/* Define to 1 if you have the Mac OS X function CFPreferencesCopyAppValue in
+   the CoreFoundation framework. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_CFPREFERENCESCOPYAPPVALUE
+#endif
+
+
 /* Define to 1 if you have the `clearerr_unlocked' function. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_CLEARERR_UNLOCKED
@@ -844,6 +864,13 @@
 #endif
 
 
+/* Define if the GNU dcgettext() function is already present or preinstalled.
+   */
+#ifndef USED_FOR_TARGET
+#undef HAVE_DCGETTEXT
+#endif
+
+
 /* Define to 1 if we found a declaration for 'abort', otherwise define to 0.
    */
 #ifndef USED_FOR_TARGET
@@ -1516,6 +1543,12 @@
 #endif
 
 
+/* Define if the GNU gettext() function is already present or preinstalled. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_GETTEXT
+#endif
+
+
 /* Define to 1 if you have the `gettimeofday' function. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_GETTIMEOFDAY
@@ -1547,7 +1580,7 @@
 #endif
 
 
-/* Define if you have the iconv() function. */
+/* Define if you have the iconv() function and it works. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_ICONV
 #endif
diff --git a/gcc/config/loongarch/genopts/loongarch.opt.in b/gcc/config/loongarch/genopts/loongarch.opt.in
index e1fe0c7..158701d 100644
--- a/gcc/config/loongarch/genopts/loongarch.opt.in
+++ b/gcc/config/loongarch/genopts/loongarch.opt.in
@@ -223,10 +223,14 @@ Target Var(TARGET_DIRECT_EXTERN_ACCESS) Init(0)
 Avoid using the GOT to access external symbols.
 
 mrelax
-Target Var(loongarch_mrelax) Init(HAVE_AS_MRELAX_OPTION)
+Target Var(loongarch_mrelax) Init(HAVE_AS_MRELAX_OPTION && HAVE_AS_COND_BRANCH_RELAXATION)
 Take advantage of linker relaxations to reduce the number of instructions
 required to materialize symbol addresses.
 
+mpass-mrelax-to-as
+Target Var(loongarch_pass_mrelax_to_as) Init(HAVE_AS_MRELAX_OPTION)
+Pass -mrelax or -mno-relax option to the assembler.
+
 -param=loongarch-vect-unroll-limit=
 Target Joined UInteger Var(loongarch_vect_unroll_limit) Init(6) IntegerRange(1, 64) Param
 Used to limit unroll factor which indicates how much the autovectorizer may
diff --git a/gcc/config/loongarch/loongarch-driver.h b/gcc/config/loongarch/loongarch-driver.h
index d859afc..20d233c 100644
--- a/gcc/config/loongarch/loongarch-driver.h
+++ b/gcc/config/loongarch/loongarch-driver.h
@@ -51,9 +51,23 @@ along with GCC; see the file COPYING3.  If not see
   "%{G*} %{,ada:-gnatea %{mabi=*} -gnatez} " \
   "%(subtarget_cc1_spec)"
 
+#if HAVE_AS_MRELAX_OPTION && HAVE_AS_COND_BRANCH_RELAXATION
+#define ASM_MRELAX_DEFAULT "%{!mrelax:%{!mno-relax:-mrelax}}"
+#else
+#define ASM_MRELAX_DEFAULT "%{!mrelax:%{!mno-relax:-mno-relax}}"
+#endif
+
+#if HAVE_AS_MRELAX_OPTION
+#define ASM_MRELAX_SPEC \
+  "%{!mno-pass-mrelax-to-as:%{mrelax} %{mno-relax} " ASM_MRELAX_DEFAULT "}"
+#else
+#define ASM_MRELAX_SPEC \
+  "%{mpass-mrelax-to-as:%{mrelax} %{mno-relax} " ASM_MRELAX_DEFAULT "}"
+#endif
+
 #undef ASM_SPEC
 #define ASM_SPEC \
-  "%{mabi=*} %{mno-relax} %(subtarget_asm_spec)"
+  "%{mabi=*} " ASM_MRELAX_SPEC " %(subtarget_asm_spec)"
 
 
 extern const char*
diff --git a/gcc/config/loongarch/loongarch-opts.h b/gcc/config/loongarch/loongarch-opts.h
index f204828..8de41bb 100644
--- a/gcc/config/loongarch/loongarch-opts.h
+++ b/gcc/config/loongarch/loongarch-opts.h
@@ -101,6 +101,10 @@ loongarch_update_gcc_opt_status (struct loongarch_target *target,
 #define HAVE_AS_MRELAX_OPTION 0
 #endif
 
+#ifndef HAVE_AS_COND_BRANCH_RELAXATION
+#define HAVE_AS_COND_BRANCH_RELAXATION 0
+#endif
+
 #ifndef HAVE_AS_TLS
 #define HAVE_AS_TLS 0
 #endif
diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
index 0a2db84..2998bf7 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -7432,7 +7432,7 @@ loongarch_option_override_internal (struct gcc_options *opts,
 
   if (la_opt_explicit_relocs == M_OPT_UNSET)
     la_opt_explicit_relocs = (HAVE_AS_EXPLICIT_RELOCS
-			      ? (HAVE_AS_MRELAX_OPTION
+			      ? (loongarch_mrelax
 				 ? EXPLICIT_RELOCS_AUTO
 				 : EXPLICIT_RELOCS_ALWAYS)
 			      : EXPLICIT_RELOCS_NONE);
diff --git a/gcc/config/loongarch/loongarch.opt b/gcc/config/loongarch/loongarch.opt
index 0294660..a598841 100644
--- a/gcc/config/loongarch/loongarch.opt
+++ b/gcc/config/loongarch/loongarch.opt
@@ -230,10 +230,14 @@ Target Var(TARGET_DIRECT_EXTERN_ACCESS) Init(0)
 Avoid using the GOT to access external symbols.
 
 mrelax
-Target Var(loongarch_mrelax) Init(HAVE_AS_MRELAX_OPTION)
+Target Var(loongarch_mrelax) Init(HAVE_AS_MRELAX_OPTION && HAVE_AS_COND_BRANCH_RELAXATION)
 Take advantage of linker relaxations to reduce the number of instructions
 required to materialize symbol addresses.
 
+mpass-mrelax-to-as
+Target Var(loongarch_pass_mrelax_to_as) Init(HAVE_AS_MRELAX_OPTION)
+Pass -mrelax or -mno-relax option to the assembler.
+
 -param=loongarch-vect-unroll-limit=
 Target Joined UInteger Var(loongarch_vect_unroll_limit) Init(6) IntegerRange(1, 64) Param
 Used to limit unroll factor which indicates how much the autovectorizer may
diff --git a/gcc/configure b/gcc/configure
index c37cae7..ee97934 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -31018,6 +31018,41 @@ $as_echo "#define HAVE_AS_MRELAX_OPTION 1" >>confdefs.h
 
 fi
 
+    { $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for conditional branch relaxation support" >&5
+$as_echo_n "checking assembler for conditional branch relaxation support... " >&6; }
+if ${gcc_cv_as_loongarch_cond_branch_relax+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  gcc_cv_as_loongarch_cond_branch_relax=no
+  if test x$gcc_cv_as != x; then
+    $as_echo 'a:
+       .rept 32769
+       nop
+       .endr
+       beq $a0,$a1,a' > conftest.s
+    if { ac_try='$gcc_cv_as $gcc_cv_as_flags  -o conftest.o conftest.s >&5'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+    then
+	gcc_cv_as_loongarch_cond_branch_relax=yes
+    else
+      echo "configure: failed program was" >&5
+      cat conftest.s >&5
+    fi
+    rm -f conftest.o conftest.s
+  fi
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $gcc_cv_as_loongarch_cond_branch_relax" >&5
+$as_echo "$gcc_cv_as_loongarch_cond_branch_relax" >&6; }
+if test $gcc_cv_as_loongarch_cond_branch_relax = yes; then
+
+$as_echo "#define HAVE_AS_COND_BRANCH_RELAXATION 1" >>confdefs.h
+
+fi
+
     ;;
     s390*-*-*)
     { $as_echo "$as_me:${as_lineno-$LINENO}: checking assembler for .gnu_attribute support" >&5
diff --git a/gcc/configure.ac b/gcc/configure.ac
index 764a33f..d0caf82 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -5453,6 +5453,16 @@ x:
       [-mrelax], [.text],,
       [AC_DEFINE(HAVE_AS_MRELAX_OPTION, 1,
 		[Define if your assembler supports -mrelax option.])])
+    gcc_GAS_CHECK_FEATURE([conditional branch relaxation support],
+      gcc_cv_as_loongarch_cond_branch_relax,
+      [],
+      [a:
+       .rept 32769
+       nop
+       .endr
+       beq $a0,$a1,a],,
+      [AC_DEFINE(HAVE_AS_COND_BRANCH_RELAXATION, 1,
+		[Define if your assembler supports conditional branch relaxation.])])
     ;;
     s390*-*-*)
     gcc_GAS_CHECK_FEATURE([.gnu_attribute support],
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index f1a5722..2d30a5d 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1045,7 +1045,7 @@ Objective-C and Objective-C++ Dialects}.
 -mmax-inline-memcpy-size=@var{n}
 -mexplicit-relocs=@var{style} -mexplicit-relocs -mno-explicit-relocs
 -mdirect-extern-access -mno-direct-extern-access
--mcmodel=@var{code-model}}
+-mcmodel=@var{code-model} -mrelax -mpass-mrelax-to-as}
 
 @emph{M32R/D Options}
 @gccoptlist{-m32r2  -m32rx  -m32r
@@ -26356,16 +26356,14 @@ with @option{-mexplicit-relocs=always} the assembler relocation operators
 are always used, with @option{-mexplicit-relocs=auto} the compiler will
 use the relocation operators where the linker relaxation is impossible to
 improve the code quality, and macros elsewhere.  The default
-value for the option is determined during GCC build-time by detecting
-corresponding assembler support:
+value for the option is determined with the assembler capability detected
+during GCC build-time and the setting of @option{-mrelax}:
 @option{-mexplicit-relocs=none} if the assembler does not support
 relocation operators at all,
 @option{-mexplicit-relocs=always} if the assembler supports relocation
-operators but does not support relaxation,
-@option{-mexplicit-relocs=auto} if the assembler supports both relocation
-operators and relaxation.  This option is mostly useful for
-debugging, or interoperation with assemblers different from the build-time
-one.
+operators but @option{-mrelax} is not enabled,
+@option{-mexplicit-relocs=auto} if the assembler supports relocation
+operators and @option{-mrelax} is enabled.
 
 @opindex mexplicit-relocs
 @item -mexplicit-relocs
@@ -26389,6 +26387,28 @@ kernels, executables linked with @option{-static} or @option{-static-pie}.
 @option{-mdirect-extern-access} is not compatible with @option{-fPIC} or
 @option{-fpic}.
 
+@item -mrelax
+@itemx -mno-relax
+Take (do not take) advantage of linker relaxations.  If
+@option{-mpass-mrelax-to-as} is enabled, this option is also passed to
+the assembler.  The default is determined during GCC build-time by
+detecting corresponding assembler support:
+@option{-mrelax} if the assembler supports both the @option{-mrelax}
+option and the conditional branch relaxation (it's required or the
+@code{.align} directives and conditional branch instructions in the
+assembly code outputted by GCC may be rejected by the assembler because
+of a relocation overflow), @option{-mno-relax} otherwise.
+
+@item -mpass-mrelax-to-as
+@itemx -mno-pass-mrelax-to-as
+Pass (do not pass) the @option{-mrelax} or @option{-mno-relax} option
+to the assembler.  The default is determined during GCC build-time by
+detecting corresponding assembler support:
+@option{-mpass-mrelax-to-as} if the assembler supports the
+@option{-mrelax} option, @option{-mno-pass-mrelax-to-as} otherwise.
+This option is mostly useful for debugging, or interoperation with
+assemblers different from the build-time one.
+
 @item loongarch-vect-unroll-limit
 The vectorizer will use available tuning information to determine whether it
 would be beneficial to unroll the main vectorized loop and by how much.  This