LoongArch processors may not support memory accesses without natural
alignments. Building libraries with -mstrict-align may help with
toolchain binary compatiblity and performance on these implementations
(e.g. Loongson 2K1000LA).
No significant performance degredation is observed on current mainstream
LoongArch processors when the option is enabled.
gcc/ChangeLog:
* config.gcc: use -mstrict-align for building libraries
if --with-strict-align-lib is given.
* doc/install.texi: likewise.
---
gcc/config.gcc | 16 +++++++++++++++-
gcc/doc/install.texi | 4 ++++
2 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/gcc/config.gcc b/gcc/config.gcc
index 4fae672a3b7..ed70fa63268 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -4892,7 +4892,7 @@ case "${target}" in
;;
loongarch*-*)
- supported_defaults="abi arch tune fpu simd multilib-default"
+ supported_defaults="abi arch tune fpu simd multilib-default
strict-align-lib"
# Local variables
unset \
@@ -5089,6 +5089,17 @@ case "${target}" in
;;
esac
+ # Build libraries with -mstrict-align if
--with-strict-align-lib is given.
+ case ${with_strict_align_lib} in
+ yes) strict_align_opt="/mstrict-align" ;;
+ ""|no) ;;
+ *)
+ echo "Unknown option:
--with-strict-align-lib=${with_strict_align_lib}" 1>&2
+ exit 1
+ ;;
+ esac
+
+
# Handle --with-multilib-default
if echo "${with_multilib_default}" \
| grep -E -e '[[:space:]]' -e '//' -e '/$' -e '^/' > /dev/null
2>&1; then
@@ -5250,6 +5261,9 @@ case "${target}" in
;;
esac
+ # Use mstrict-align for building libraries if
--with-strict-align-lib is given.
+
loongarch_multilib_list_make="${loongarch_multilib_list_make}${strict_align_opt}"
+
# Check for repeated configuration of the same multilib
variant.
if echo "${elem_abi_base}/${elem_abi_ext}" \
| grep -E "^(${all_abis%|})$" >/dev/null 2>&1; then
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index bbc58cb60ca..31f2234640f 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -1416,6 +1416,10 @@ Multiple @var{option}s may appear consecutively while
@var{arch} may only
appear in the beginning or be omitted (which means @option{-march=abi-default}
is applied when building the libraries).
+@item --with-strict-align-lib
+On LoongArch targets, build all enabled multilibs with @option{-mstrict-align}
+(Not enabled by default).
+
@item --with-multilib-generator=@var{config}
Specify what multilibs to build. @var{config} is a semicolon separated list of
values, possibly consisting of a single value. Currently only implemented
--
2.36.0
