From bb019bc68f228963dc5d31c84cbe41662791792e Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Thu, 9 Oct 2025 20:44:59 +0200 Subject: [PATCH] i386: Use __seg_gs qualifiers in PTR_{MANGLE,DEMANGLE}() macros Use __seg_gs named address space qualifiers in PTR_MANGLE() and PTR_DEMANGLE() macros to access the pointer_guard field in the TCB. This change allows the compiler to eliminate redundant reads of the variable, reducing the number of reads from 105 to 94 and decreasing the text size of the library by 280 bytes. While at it, fix a few trivial whitespace issues as well Signed-off-by: Uros Bizjak Reviewed-by: H.J. Lu --- sysdeps/unix/sysv/linux/i386/pointer_guard.h | 31 +++++++++++--------- 1 file changed, 17 insertions(+), 14 deletions(-) diff --git a/sysdeps/unix/sysv/linux/i386/pointer_guard.h b/sysdeps/unix/sysv/linux/i386/pointer_guard.h index ae27c82a62..0162178f47 100644 --- a/sysdeps/unix/sysv/linux/i386/pointer_guard.h +++ b/sysdeps/unix/sysv/linux/i386/pointer_guard.h @@ -28,21 +28,24 @@ # include #else # ifdef __ASSEMBLER__ -# define PTR_MANGLE(reg) xorl %gs:POINTER_GUARD, reg; \ - roll $9, reg -# define PTR_DEMANGLE(reg) rorl $9, reg; \ - xorl %gs:POINTER_GUARD, reg +# define PTR_MANGLE(reg) xorl %gs:POINTER_GUARD, reg; \ + roll $9, reg +# define PTR_DEMANGLE(reg) rorl $9, reg; \ + xorl %gs:POINTER_GUARD, reg # else -# define PTR_MANGLE(var) asm ("xorl %%gs:%c2, %0\n" \ - "roll $9, %0" \ - : "=r" (var) \ - : "0" (var), \ - "i" (POINTER_GUARD)) -# define PTR_DEMANGLE(var) asm ("rorl $9, %0\n" \ - "xorl %%gs:%c2, %0" \ - : "=r" (var) \ - : "0" (var), \ - "i" (POINTER_GUARD)) +# include +# define PTR_MANGLE(var) do \ + { \ + (var) = (__typeof (var)) ((uintptr_t) (var) \ + ^ ((tcbhead_t __seg_gs *)0)->pointer_guard); \ + asm ("roll $9, %0" : "+r" (var)); \ + } while (0) +# define PTR_DEMANGLE(var) do \ + { \ + asm ("rorl $9, %0" : "+r" (var)); \ + (var) = (__typeof (var)) ((uintptr_t) (var) \ + ^ ((tcbhead_t __seg_gs *)0)->pointer_guard); \ + } while (0) # endif #endif -- 2.47.3