From e8a0d2b477d8da7a087bef98feb7e08d320b8051 Mon Sep 17 00:00:00 2001
From: YANG XIN <yangxin.dev@bytedance.com>
Date: Mon, 22 Jun 2026 16:57:49 +0800
Subject: [PATCH] Fix rdtscp detection with --with-lg-vaddr

The rdtscp probe was nested inside the x86_64 LG_VADDR auto-detection block. Passing --with-lg-vaddr skipped the probe and left JEMALLOC_HAVE_RDTSCP undefined even when the instruction was available.

Keep the probe in the x86_64 branch, but run it independently from LG_VADDR auto-detection.
---
 configure.ac | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/configure.ac b/configure.ac
index 6532af1c..c2b83a1f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -600,9 +600,10 @@ typedef unsigned __int32 uint32_t;
       else
         AC_MSG_ERROR([cannot determine number of significant virtual address bits])
       fi
-      AC_CACHE_CHECK([rdtscp support],
-		     [je_cv_rdtscp],
-		     AC_RUN_IFELSE([AC_LANG_PROGRAM(
+    fi
+    AC_CACHE_CHECK([rdtscp support],
+		   [je_cv_rdtscp],
+		   AC_RUN_IFELSE([AC_LANG_PROGRAM(
 [[
 #include <stdint.h>
 ]],
@@ -611,12 +612,11 @@ typedef unsigned __int32 uint32_t;
       asm volatile("rdtscp" : "=d"(dx) ::);
       return 0;
 ]])],
-      [je_cv_rdtscp=yes],
-      [je_cv_rdtscp=no],
-      [je_cv_rdtscp=no]))
-      if test "x${je_cv_rdtscp}" = "xyes"; then
-        AC_DEFINE([JEMALLOC_HAVE_RDTSCP], [ ], [ ])
-      fi
+    [je_cv_rdtscp=yes],
+    [je_cv_rdtscp=no],
+    [je_cv_rdtscp=no]))
+    if test "x${je_cv_rdtscp}" = "xyes"; then
+      AC_DEFINE([JEMALLOC_HAVE_RDTSCP], [ ], [ ])
     fi
     ;;
   *)