gcc: Add --enable-multilib-space option

This option adds a per-multilib variant that specifies -Os
instead of the default.

Signed-off-by: Keith Packard <[email protected]>

Author: keith-packard

config-ml.in

@@ -175,7 +175,7 @@ eval scan_arguments "${ac_configure_args}"
 unset scan_arguments
 
 # Only do this if --enable-multilib.
-if [ "${enable_multilib}" = yes ]; then
+if [ "${enable_multilib}" = yes -o "${enable_multilib_space}" = yes ]; then
 
 # Compute whether this is the library's top level directory
 # (ie: not a multilib subdirectory, and not a subdirectory like newlib/src).

gcc/Makefile.in

@@ -2296,25 +2296,47 @@ libgcc.mvars: config.status Makefile specs xgcc$(exeext)
 
 	mv tmp-libgcc.mvars libgcc.mvars
 
+ifeq (@enable_multilib_space@,yes)
+MULTILIB_OPTIONS	+= Os
+MULTILIB_DIRNAMES	+= space
+MULTILIB_MATCHES	+= Os=Oz
+
+MULTILIB_OSDIRNAMES_SPACE = $(MULTILIB_OSDIRNAMES)\
+	$(if $(findstring =,$(MULTILIB_OSDIRNAMES)),\
+	  $(foreach OSD,$(MULTILIB_OSDIRNAMES),$(subst =,/Os=,$(OSD))/space),\
+	  $(if $(MULTILIB_OSDIRNAMES),space,))
+MULTILIB_REQUIRED_SPACE = $(if $(MULTILIB_REQUIRED),Os $(foreach REQ, $(MULTILIB_REQUIRED), $(REQ) $(REQ)/Os),)
+MULTILIB_EXCEPTIONS_SPACE = $(foreach EXC, $(MULTILIB_EXCEPTIONS), $(EXC) $(EXC)/Os)
+MULTILIB_REUSE_SPACE = $(foreach REU, $(MULTILIB_REUSE), $(REU) $(subst =,/Os=,$(REU))/Os)
+MULTILIB_ENABLE = yes
+else
+MULTILIB_OSDIRNAMES_SPACE = $(MULTILIB_OSDIRNAMES)
+MULTILIB_REQUIRED_SPACE = $(MULTILIB_REQUIRED)
+MULTILIB_EXCEPTIONS_SPACE = $(MULTILIB_EXCEPTIONS)
+MULTILIB_REUSE_SPACE = $(MULTILIB_REUSE)
+MULTILIB_ENABLE = @enable_multilib@
+endif
+
 # Use the genmultilib shell script to generate the information the gcc
 # driver program needs to select the library directory based on the
 # switches.
 multilib.h: s-mlib; @true
 s-mlib: $(srcdir)/genmultilib Makefile
 	if test @enable_multilib@ = yes \
+           || test @enable_multilib_space@ = yes \
 	   || test -n "$(MULTILIB_OSDIRNAMES)"; then \
 	  $(SHELL) $(srcdir)/genmultilib \
 	    "$(MULTILIB_OPTIONS)" \
 	    "$(MULTILIB_DIRNAMES)" \
 	    "$(MULTILIB_MATCHES)" \
-	    "$(MULTILIB_EXCEPTIONS)" \
+	    "$(MULTILIB_EXCEPTIONS_SPACE)" \
 	    "$(MULTILIB_EXTRA_OPTS)" \
 	    "$(MULTILIB_EXCLUSIONS)" \
-	    "$(MULTILIB_OSDIRNAMES)" \
-	    "$(MULTILIB_REQUIRED)" \
+	    "$(MULTILIB_OSDIRNAMES_SPACE)" \
+	    "$(MULTILIB_REQUIRED_SPACE)" \
 	    "$(if $(MULTILIB_OSDIRNAMES),,$(MULTIARCH_DIRNAME))" \
-	    "$(MULTILIB_REUSE)" \
-	    "@enable_multilib@" \
+	    "$(MULTILIB_REUSE_SPACE)" \
+	    "$(MULTILIB_ENABLE)" \
 	    > tmp-mlib.h; \
 	else \
 	  $(SHELL) $(srcdir)/genmultilib '' '' '' '' '' '' '' '' \

gcc/configure

@@ -857,6 +857,7 @@ DEFAULT_MATCHPD_PARTITIONS
 with_float
 with_cpu
 enable_multiarch
+enable_multilib_space
 enable_multilib
 coverage_flags
 valgrind_command
@@ -979,6 +980,7 @@ enable_coverage
 enable_gather_detailed_mem_stats
 enable_valgrind_annotations
 enable_multilib
+enable_multilib_space
 enable_multiarch
 with_stack_clash_protection_guard_size
 with_matchpd_partitions
@@ -1720,6 +1722,7 @@ Optional Features:
   --enable-valgrind-annotations
                           enable valgrind runtime interaction
   --enable-multilib       enable library support for multiple ABIs
+  --enable-multilib-space enable extra -Os variant for every multilib ABI
   --enable-multiarch      enable support for multiarch paths
   --enable-__cxa_atexit   enable __cxa_atexit for C++
   --enable-decimal-float={no,yes,bid,dpd}
@@ -7840,6 +7843,16 @@ fi
 
 
 
+# Determine whether or not -Os multilibs are enabled.
+# Check whether --enable-multilib-space was given.
+if test "${enable_multilib_space+set}" = set; then :
+  enableval=$enable_multilib_space;
+else
+  enable_multilib_space=no
+fi
+
+
+
 # Determine whether or not multiarch is enabled.
 # Check whether --enable-multiarch was given.
 if test "${enable_multiarch+set}" = set; then :

gcc/configure.ac

@@ -852,6 +852,13 @@ AC_ARG_ENABLE(multilib,
 [], [enable_multilib=yes])
 AC_SUBST(enable_multilib)
 
+# Determine whether or not -Os multilibs are enabled.
+AC_ARG_ENABLE(multilib-space,
+[AS_HELP_STRING([--enable-multilib-space],
+		[enable extra -Os variant for every multilib ABI])],
+[], [enable_multilib_space=no])
+AC_SUBST(enable_multilib_space)
+
 # Determine whether or not multiarch is enabled.
 AC_ARG_ENABLE(multiarch,
 [AS_HELP_STRING([--enable-multiarch],

gcc/doc/install.texi

@@ -1268,6 +1268,18 @@ for aarch64*-*-*, amdgcn*-*-*, arm*-*-*, loongarch*-*-*, riscv*-*-*, sh*-*-*
 and x86-64-*-linux*.  The accepted values and meaning for each target is given
 below.
 
+@item --enable-multilib-space
+Double the set of target libraries built by building two versions of
+each specified by the options above, one using @option{-O2 }and
+another using @option{-Os}. During linking, the @option{-O2} variant
+will be selected by default. Select the @option{-Os} variant by
+including @option{-Os} or @option{-Oz} in the linker command
+line. Note: because multilib selection only looks for the presence of
+compiler flags (unlike options controlling the compiler optimization
+level), a subsequent optimization flag other than @option{-Os} or or
+@option{-Oz} will not switch back to the @option{-O2} library
+versions.
+
 @table @code
 @item aarch64*-*-*
 @var{list} is a comma separated list of @code{ilp32}, and @code{lp64}