[gcc(refs/vendors/ARM/heads/morello)] Make GCC build a purecap libgcc as a multilib

[Matthew Malcomson <matmal01@gcc.gnu.org>]

https://gcc.gnu.org/g:1f949c3d085a8994cd7579250b77197c23db435a

commit 1f949c3d085a8994cd7579250b77197c23db435a
Author: Matthew Malcomson <matthew.malcomson@arm.com>
Date:   Mon Aug 9 10:52:40 2021 +0100

    Make GCC build a purecap libgcc as a multilib
    
    This means we can simply build an aarch64-none-elf cross compiler and
    have it generate the -march=morello+c64 -mabi=purecap libgcc as
    necessary.
    
    Note that this means we need the Morello binutils in our path whenever
    compiling an aarch64-none-elf toolchain unless we specifically request
    to avoid making the purecap multilib.
    
    Have enabled using --with-multilib-list=purecap but not added that
    multilib to the default list on aarch64-none-linux-gnu.  We can't build
    these purecap libraries on aarch64 linux since there are other blockers
    (like enabling GCC in total so we can build glibc).  Hence this is not
    getting tested at the moment (have tested that attempting to build
    libgcc purecap multilib at least gets past the configure stage, but we
    fail on having the relevant glibc headers in a purecap multilib
    subdirectory).

Diff:
---
 gcc/config.gcc               | 6 +++---
 gcc/config/aarch64/t-aarch64 | 5 ++++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/gcc/config.gcc b/gcc/config.gcc
index 23703681deb..bcc9a94d79f 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -1056,12 +1056,12 @@ aarch64*-*-elf | aarch64*-*-fuchsia* | aarch64*-*-rtems*)
 	esac
 	aarch64_multilibs="${with_multilib_list}"
 	if test "$aarch64_multilibs" = "default"; then
-		aarch64_multilibs="lp64,ilp32"
+		aarch64_multilibs="lp64,ilp32,purecap"
 	fi
 	aarch64_multilibs=`echo $aarch64_multilibs | sed -e 's/,/ /g'`
 	for aarch64_multilib in ${aarch64_multilibs}; do
 		case ${aarch64_multilib} in
-		ilp32 | lp64 )
+		ilp32 | lp64 | purecap )
 			TM_MULTILIB_CONFIG="${TM_MULTILIB_CONFIG},${aarch64_multilib}"
 			;;
 		*)
@@ -1102,7 +1102,7 @@ aarch64*-*-linux*)
 	aarch64_multilibs=`echo $aarch64_multilibs | sed -e 's/,/ /g'`
 	for aarch64_multilib in ${aarch64_multilibs}; do
 		case ${aarch64_multilib} in
-		ilp32 | lp64 )
+		ilp32 | lp64 | purecap )
 			TM_MULTILIB_CONFIG="${TM_MULTILIB_CONFIG},${aarch64_multilib}"
 			;;
 		*)
diff --git a/gcc/config/aarch64/t-aarch64 b/gcc/config/aarch64/t-aarch64
index 11d20b7be14..a05eecd129d 100644
--- a/gcc/config/aarch64/t-aarch64
+++ b/gcc/config/aarch64/t-aarch64
@@ -159,7 +159,10 @@ aarch64-bti-insert.o: $(srcdir)/config/aarch64/aarch64-bti-insert.c \
 		$(srcdir)/config/aarch64/aarch64-bti-insert.c
 
 comma=,
-MULTILIB_OPTIONS    = $(subst $(comma),/, $(patsubst %, mabi=%, $(subst $(comma),$(comma)mabi=,$(TM_MULTILIB_CONFIG))))
+MULTILIB_OPTIONS    = $(subst $(comma),/, $(patsubst %, mabi=%, $(subst $(comma),$(comma)mabi=,$(TM_MULTILIB_CONFIG)))) march=morello+c64
+MULTILIB_EXCEPTIONS = mabi=*lp*/march=morello+c64
+MULTILIB_EXCEPTIONS += mabi=purecap
+MULTILIB_EXCEPTIONS += march=morello+c64
 MULTILIB_DIRNAMES   = $(subst $(comma), ,$(TM_MULTILIB_CONFIG))
 
 insn-conditions.md: s-check-sve-md