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Refactor LG_VADDR detection in configure.ac

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The LG_VADDR detection block accumulated duplicated logic and the rdtscp
feature probe was interleaved with virtual-address-bit detection.

Consolidate the detection:
- Wrap the whole case in a single "if LG_VADDR = detect" guard instead
  of repeating it in every "case" section.
- Define LG_VADDR exactly once, after the case.
- Check the cache variable directly for the x86_64 error path.
- Move the rdtscp probe into its own x86_64 case so it stays independent
  of LG_VADDR detection (it must run even when --with-lg-vaddr is given).

There is no functional change. Verified on x86_64 that LG_VADDR and
JEMALLOC_HAVE_RDTSCP are identical to before for auto-detection, and that
--with-lg-vaddr still probes rdtscp.
This commit is contained in:
Schalk Krüger 2026-07-15 13:40:27 -07:00 • committed by Guangli Dai
parent 68c35f6557
commit b44e84086f
1 changed files with 29 additions and 27 deletions
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56
configure.ac
View file

@ -533,13 +533,14 @@ esac
AC_DEFINE_UNQUOTED([HAVE_CPU_SPINWAIT], [$HAVE_CPU_SPINWAIT], [ ])
AC_DEFINE_UNQUOTED([CPU_SPINWAIT], [$CPU_SPINWAIT], [ ])
dnl LG_VADDR: number of significant virtual address bits. Auto-detected when --with-lg-vaddr is left unset.
AC_ARG_WITH([lg_vaddr],
[AS_HELP_STRING([--with-lg-vaddr=<lg-vaddr>], [Number of significant virtual address bits])],
[LG_VADDR="$with_lg_vaddr"], [LG_VADDR="detect"])
case "${host_cpu}" in
aarch64)
if test "x$LG_VADDR" = "xdetect"; then
if test "x$LG_VADDR" = "xdetect"; then
case "${host_cpu}" in
aarch64)
AC_MSG_CHECKING([number of significant virtual address bits])
if test "x${LG_SIZEOF_PTR}" = "x2" ; then
#aarch64 ILP32
@ -549,10 +550,8 @@ case "${host_cpu}" in
LG_VADDR=48
fi
AC_MSG_RESULT([$LG_VADDR])
fi
;;
x86_64)
if test "x$LG_VADDR" = "xdetect"; then
;;
x86_64)
AC_CACHE_CHECK([number of significant virtual address bits],
[je_cv_lg_vaddr],
AC_RUN_IFELSE([AC_LANG_PROGRAM(
@ -592,15 +591,33 @@ typedef unsigned __int32 uint32_t;
[je_cv_lg_vaddr=`cat conftest.out`],
[je_cv_lg_vaddr=error],
[je_cv_lg_vaddr=57]))
if test "x${je_cv_lg_vaddr}" = "xerror" ; then
AC_MSG_ERROR([cannot determine number of significant virtual address bits])
fi
if test "x${je_cv_lg_vaddr}" != "x" ; then
LG_VADDR="${je_cv_lg_vaddr}"
fi
if test "x${LG_VADDR}" != "xerror" ; then
AC_DEFINE_UNQUOTED([LG_VADDR], [$LG_VADDR], [ ])
;;
*)
AC_MSG_CHECKING([number of significant virtual address bits])
if test "x${LG_SIZEOF_PTR}" = "x3" ; then
LG_VADDR=64
elif test "x${LG_SIZEOF_PTR}" = "x2" ; then
LG_VADDR=32
elif test "x${LG_SIZEOF_PTR}" = "xLG_SIZEOF_PTR_WIN" ; then
LG_VADDR="(1U << (LG_SIZEOF_PTR_WIN+3))"
else
AC_MSG_ERROR([cannot determine number of significant virtual address bits])
AC_MSG_ERROR([Unsupported lg(pointer size): ${LG_SIZEOF_PTR}])
fi
fi
AC_MSG_RESULT([$LG_VADDR])
;;
esac
fi
AC_DEFINE_UNQUOTED([LG_VADDR], [$LG_VADDR], [ ])
dnl rdtscp feature probe for x86_64
case "${host_cpu}" in
x86_64)
AC_CACHE_CHECK([rdtscp support],
[je_cv_rdtscp],
AC_RUN_IFELSE([AC_LANG_PROGRAM(
@ -619,23 +636,8 @@ typedef unsigned __int32 uint32_t;
AC_DEFINE([JEMALLOC_HAVE_RDTSCP], [ ], [ ])
fi
;;
*)
if test "x$LG_VADDR" = "xdetect"; then
AC_MSG_CHECKING([number of significant virtual address bits])
if test "x${LG_SIZEOF_PTR}" = "x3" ; then
LG_VADDR=64
elif test "x${LG_SIZEOF_PTR}" = "x2" ; then
LG_VADDR=32
elif test "x${LG_SIZEOF_PTR}" = "xLG_SIZEOF_PTR_WIN" ; then
LG_VADDR="(1U << (LG_SIZEOF_PTR_WIN+3))"
else
AC_MSG_ERROR([Unsupported lg(pointer size): ${LG_SIZEOF_PTR}])
fi
AC_MSG_RESULT([$LG_VADDR])
fi
;;
esac
AC_DEFINE_UNQUOTED([LG_VADDR], [$LG_VADDR], [ ])
AC_CACHE_CHECK([asm volatile support],
[je_cv_asm_volatile],
AC_RUN_IFELSE([AC_LANG_PROGRAM(