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-rw-r--r--m4/tuklib_integer.m434
1 files changed, 27 insertions, 7 deletions
diff --git a/m4/tuklib_integer.m4 b/m4/tuklib_integer.m4
index ab9a4056..89a53fe1 100644
--- a/m4/tuklib_integer.m4
+++ b/m4/tuklib_integer.m4
@@ -65,22 +65,42 @@ AC_MSG_CHECKING([if unaligned memory access should be used])
AC_ARG_ENABLE([unaligned-access], AS_HELP_STRING([--enable-unaligned-access],
[Enable if the system supports *fast* unaligned memory access
with 16-bit, 32-bit, and 64-bit integers. By default,
- this is enabled only on x86, x86_64, big endian PowerPC,
- and some ARM systems.]),
+ this is enabled on x86, x86-64,
+ 32/64-bit big endian PowerPC,
+ 64-bit little endian PowerPC,
+ and some ARM, ARM64, and RISC-V systems.]),
[], [enable_unaligned_access=auto])
if test "x$enable_unaligned_access" = xauto ; then
- # TODO: There may be other architectures, on which unaligned access
- # is OK.
+ # NOTE: There might be other architectures on which unaligned access
+ # is fast.
case $host_cpu in
- i?86|x86_64|powerpc|powerpc64)
+ i?86|x86_64|powerpc|powerpc64|powerpc64le)
enable_unaligned_access=yes
;;
- arm*|aarch64*)
+ arm*|aarch64*|riscv*)
# On 32-bit and 64-bit ARM, GCC and Clang
# #define __ARM_FEATURE_UNALIGNED if
# unaligned access is supported.
+ #
+ # Exception: GCC at least up to 13.2.0
+ # defines it even when using -mstrict-align
+ # so in that case this autodetection goes wrong.
+ # Most of the time -mstrict-align isn't used so it
+ # shouldn't be a common problem in practice. See:
+ # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111555
+ #
+ # RISC-V C API Specification says that if
+ # __riscv_misaligned_fast is defined then
+ # unaligned access is known to be fast.
+ #
+ # MSVC is handled as a special case: We assume that
+ # 32/64-bit ARM supports fast unaligned access.
+ # If MSVC gets RISC-V support then this will assume
+ # fast unaligned access on RISC-V too.
AC_COMPILE_IFELSE([AC_LANG_SOURCE([
-#ifndef __ARM_FEATURE_UNALIGNED
+#if !defined(__ARM_FEATURE_UNALIGNED) \
+ && !defined(__riscv_misaligned_fast) \
+ && !defined(_MSC_VER)
compile error
#endif
int main(void) { return 0; }