[glibc] x86_64: Replace inline asm rotates in pointer_guard with stdc_rotate_{left, right}

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=63545c6d2c5c5a9b5259761b23eb6996bb71187f

commit 63545c6d2c5c5a9b5259761b23eb6996bb71187f
Author: Uros Bizjak <[email protected]>
Date:   Wed May 6 17:05:46 2026 +0200

    x86_64: Replace inline asm rotates in pointer_guard with stdc_rotate_{left,right}
    
    Use the C23 <stdbit.h> rotation helpers instead of inline assembly
    for pointer mangling and demangling on x86_64.
    
    The PTR_MANGLE and PTR_DEMANGLE macros previously used rol/ror
    inline asm with a constant rotation of 2 * LP_SIZE + 1. Replace
    these with stdc_rotate_left and stdc_rotate_right operating on
    uintptr_t, preserving the exact rotation count via
    2 * sizeof (uintptr_t) + 1.
    
    This change removes inline assembly, improves portability and
    readability and lets the compiler select optimal code generation.
    
    No functional change intended.
    
    Signed-off-by: Uros Bizjak <[email protected]>
    Reviewed-by: Adhemerval Zanella  <[email protected]>

Diff:
---
 sysdeps/unix/sysv/linux/x86_64/pointer_guard.h | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/x86_64/pointer_guard.h b/sysdeps/unix/sysv/linux/x86_64/pointer_guard.h
index 898a2dd3ed..4f7abc64f4 100644
--- a/sysdeps/unix/sysv/linux/x86_64/pointer_guard.h
+++ b/sysdeps/unix/sysv/linux/x86_64/pointer_guard.h
@@ -31,17 +31,20 @@
 #  define PTR_DEMANGLE(reg)	ror $2*LP_SIZE+1, reg;			      \
 				xor __pointer_chk_guard_local(%rip), reg
 # else
+#  include <stdbit.h>
 #  include <stdint.h>
 extern uintptr_t __pointer_chk_guard_local attribute_relro attribute_hidden;
 #  define PTR_MANGLE(var)						      \
     do {								      \
       (var) = (__typeof (var)) ((uintptr_t) (var)			      \
 				^ __pointer_chk_guard_local);		      \
-      asm ("rol $2*" LP_SIZE "+1, %0" : "+r" (var));			      \
+      (var) = (__typeof (var)) stdc_rotate_left ((uintptr_t) (var),	      \
+						 2 * sizeof (uintptr_t) + 1); \
     } while (0)
 #  define PTR_DEMANGLE(var)						      \
     do {								      \
-      asm ("ror $2*" LP_SIZE "+1, %0" : "+r" (var));			      \
+      (var) = (__typeof (var)) stdc_rotate_right ((uintptr_t) (var),	      \
+						  2 * sizeof (uintptr_t) + 1); \
       (var) = (__typeof (var)) ((uintptr_t) (var)			      \
 				^ __pointer_chk_guard_local);		      \
     } while (0)
@@ -53,16 +56,19 @@ extern uintptr_t __pointer_chk_guard_local attribute_relro attribute_hidden;
 #  define PTR_DEMANGLE(reg)	ror $2*LP_SIZE+1, reg;			      \
 				xor %fs:POINTER_GUARD, reg
 # else
+#  include <stdbit.h>
 #  include <tls.h>
 #  define PTR_MANGLE(var)						      \
     do {								      \
       (var) = (__typeof (var)) ((uintptr_t) (var)			      \
 				^ ((tcbhead_t __seg_fs *)0)->pointer_guard);  \
-      asm ("rol $2*" LP_SIZE "+1, %0" : "+r" (var));			      \
+      (var) = (__typeof (var)) stdc_rotate_left ((uintptr_t) (var),	      \
+						 2 * sizeof (uintptr_t) + 1); \
     } while (0)
 #  define PTR_DEMANGLE(var)						      \
     do {								      \
-      asm ("ror $2*" LP_SIZE "+1, %0" : "+r" (var));			      \
+      (var) = (__typeof (var)) stdc_rotate_right ((uintptr_t) (var),	      \
+						  2 * sizeof (uintptr_t) + 1); \
       (var) = (__typeof (var)) ((uintptr_t) (var)			      \
 				^ ((tcbhead_t __seg_fs *)0)->pointer_guard);  \
     } while (0)