[PATCH 1/5] x86: Remove unused atomics
Uros Bizjak
ubizjak@gmail.com
Mon Sep 8 12:38:19 GMT 2025
Remove unused atomics from <sysdeps/x86/atomic-machine.h>.
The resulting libc.so is identical on both x86_64 and
i386 targets compared to unpatched builds:
$ sha1sum libc-x86_64-old.so libc-x86_64-new.so
b89aaa2b71efd435104ebe6f4cd0f2ef89fcac90 libc-x86_64-old.so
b89aaa2b71efd435104ebe6f4cd0f2ef89fcac90 libc-x86_64-new.so
$ sha1sum libc-i386-old.so libc-i386-new.so
aa70f2d64da2f0f516634b116014cfe7af3e5b1a libc-i386-old.so
aa70f2d64da2f0f516634b116014cfe7af3e5b1a libc-i386-new.so
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
Cc: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Cc: Collin Funk <collin.funk1@gmail.com>
Cc: H.J.Lu <hjl.tools@gmail.com>
Cc: Carlos O'Donell <carlos@redhat.com>
---
sysdeps/x86/atomic-machine.h | 353 -----------------------------------
1 file changed, 353 deletions(-)
diff --git a/sysdeps/x86/atomic-machine.h b/sysdeps/x86/atomic-machine.h
index ac59f77e43..9b5019c4f1 100644
--- a/sysdeps/x86/atomic-machine.h
+++ b/sysdeps/x86/atomic-machine.h
@@ -32,7 +32,6 @@
# define SP_REG "rsp"
# define SEG_REG "fs"
# define BR_CONSTRAINT "q"
-# define IBR_CONSTRAINT "iq"
#else
/* Since the Pentium, i386 CPUs have supported 64-bit atomics, but the
i386 psABI supplement provides only 4-byte alignment for uint64_t
@@ -42,7 +41,6 @@
# define SP_REG "esp"
# define SEG_REG "gs"
# define BR_CONSTRAINT "r"
-# define IBR_CONSTRAINT "ir"
#endif
#define ATOMIC_EXCHANGE_USES_CAS 0
@@ -98,15 +96,8 @@
"0" ((int64_t) cast_to_integer (oldval)), \
"i" (offsetof (tcbhead_t, multiple_threads))); \
ret; })
-# define do_exchange_and_add_val_64_acq(pfx, mem, value) 0
# define do_add_val_64_acq(pfx, mem, value) do { } while (0)
#else
-/* XXX We do not really need 64-bit compare-and-exchange. At least
- not in the moment. Using it would mean causing portability
- problems since not many other 32-bit architectures have support for
- such an operation. So don't define any code for now. If it is
- really going to be used the code below can be used on Intel Pentium
- and later, but NOT on i486. */
# define __arch_c_compare_and_exchange_val_64_acq(mem, newval, oldval) \
({ __typeof (*mem) ret = *(mem); \
__atomic_link_error (); \
@@ -114,25 +105,6 @@
ret = (oldval); \
ret; })
-# define __arch_compare_and_exchange_val_64_acq(mem, newval, oldval) \
- ({ __typeof (*mem) ret = *(mem); \
- __atomic_link_error (); \
- ret = (newval); \
- ret = (oldval); \
- ret; })
-
-# define do_exchange_and_add_val_64_acq(pfx, mem, value) \
- ({ __typeof (value) __addval = (value); \
- __typeof (*mem) __result; \
- __typeof (mem) __memp = (mem); \
- __typeof (*mem) __tmpval; \
- __result = *__memp; \
- do \
- __tmpval = __result; \
- while ((__result = pfx##_compare_and_exchange_val_64_acq \
- (__memp, __result + __addval, __result)) == __tmpval); \
- __result; })
-
# define do_add_val_64_acq(pfx, mem, value) \
{ \
__typeof (value) __addval = (value); \
@@ -174,193 +146,6 @@
} \
result; })
-
-#define __arch_exchange_and_add_body(lock, pfx, mem, value) \
- ({ __typeof (*mem) __result; \
- __typeof (value) __addval = (value); \
- if (sizeof (*mem) == 1) \
- __asm __volatile (lock "xaddb %b0, %1" \
- : "=q" (__result), "=m" (*mem) \
- : "0" (__addval), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (sizeof (*mem) == 2) \
- __asm __volatile (lock "xaddw %w0, %1" \
- : "=r" (__result), "=m" (*mem) \
- : "0" (__addval), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (sizeof (*mem) == 4) \
- __asm __volatile (lock "xaddl %0, %1" \
- : "=r" (__result), "=m" (*mem) \
- : "0" (__addval), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (__HAVE_64B_ATOMICS) \
- __asm __volatile (lock "xaddq %q0, %1" \
- : "=r" (__result), "=m" (*mem) \
- : "0" ((int64_t) cast_to_integer (__addval)), \
- "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else \
- __result = do_exchange_and_add_val_64_acq (pfx, (mem), __addval); \
- __result; })
-
-#define atomic_exchange_and_add(mem, value) \
- __sync_fetch_and_add (mem, value)
-
-#define __arch_exchange_and_add_cprefix \
- "cmpl $0, %%" SEG_REG ":%P4\n\tje 0f\n\tlock\n0:\t"
-
-#define catomic_exchange_and_add(mem, value) \
- __arch_exchange_and_add_body (__arch_exchange_and_add_cprefix, __arch_c, \
- mem, value)
-
-
-#define __arch_add_body(lock, pfx, apfx, mem, value) \
- do { \
- if (__builtin_constant_p (value) && (value) == 1) \
- pfx##_increment (mem); \
- else if (__builtin_constant_p (value) && (value) == -1) \
- pfx##_decrement (mem); \
- else if (sizeof (*mem) == 1) \
- __asm __volatile (lock "addb %b1, %0" \
- : "=m" (*mem) \
- : IBR_CONSTRAINT (value), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (sizeof (*mem) == 2) \
- __asm __volatile (lock "addw %w1, %0" \
- : "=m" (*mem) \
- : "ir" (value), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (sizeof (*mem) == 4) \
- __asm __volatile (lock "addl %1, %0" \
- : "=m" (*mem) \
- : "ir" (value), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (__HAVE_64B_ATOMICS) \
- __asm __volatile (lock "addq %q1, %0" \
- : "=m" (*mem) \
- : "ir" ((int64_t) cast_to_integer (value)), \
- "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else \
- do_add_val_64_acq (apfx, (mem), (value)); \
- } while (0)
-
-# define atomic_add(mem, value) \
- __arch_add_body (LOCK_PREFIX, atomic, __arch, mem, value)
-
-#define __arch_add_cprefix \
- "cmpl $0, %%" SEG_REG ":%P3\n\tje 0f\n\tlock\n0:\t"
-
-#define catomic_add(mem, value) \
- __arch_add_body (__arch_add_cprefix, atomic, __arch_c, mem, value)
-
-
-#define atomic_add_negative(mem, value) \
- ({ _Bool __result; \
- if (sizeof (*mem) == 1) \
- __asm __volatile (LOCK_PREFIX "addb %b2, %0" \
- : "=m" (*mem), "=@ccs" (__result) \
- : IBR_CONSTRAINT (value), "m" (*mem)); \
- else if (sizeof (*mem) == 2) \
- __asm __volatile (LOCK_PREFIX "addw %w2, %0" \
- : "=m" (*mem), "=@ccs" (__result) \
- : "ir" (value), "m" (*mem)); \
- else if (sizeof (*mem) == 4) \
- __asm __volatile (LOCK_PREFIX "addl %2, %0" \
- : "=m" (*mem), "=@ccs" (__result) \
- : "ir" (value), "m" (*mem)); \
- else if (__HAVE_64B_ATOMICS) \
- __asm __volatile (LOCK_PREFIX "addq %q2, %0" \
- : "=m" (*mem), "=@ccs" (__result) \
- : "ir" ((int64_t) cast_to_integer (value)), \
- "m" (*mem)); \
- else \
- __atomic_link_error (); \
- __result; })
-
-
-#define atomic_add_zero(mem, value) \
- ({ _Bool __result; \
- if (sizeof (*mem) == 1) \
- __asm __volatile (LOCK_PREFIX "addb %b2, %0" \
- : "=m" (*mem), "=@ccz" (__result) \
- : IBR_CONSTRAINT (value), "m" (*mem)); \
- else if (sizeof (*mem) == 2) \
- __asm __volatile (LOCK_PREFIX "addw %w2, %0" \
- : "=m" (*mem), "=@ccz" (__result) \
- : "ir" (value), "m" (*mem)); \
- else if (sizeof (*mem) == 4) \
- __asm __volatile (LOCK_PREFIX "addl %2, %0" \
- : "=m" (*mem), "=@ccz" (__result) \
- : "ir" (value), "m" (*mem)); \
- else if (__HAVE_64B_ATOMICS) \
- __asm __volatile (LOCK_PREFIX "addq %q2, %0" \
- : "=m" (*mem), "=@ccz" (__result) \
- : "ir" ((int64_t) cast_to_integer (value)), \
- "m" (*mem)); \
- else \
- __atomic_link_error (); \
- __result; })
-
-
-#define __arch_increment_body(lock, pfx, mem) \
- do { \
- if (sizeof (*mem) == 1) \
- __asm __volatile (lock "incb %b0" \
- : "=m" (*mem) \
- : "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (sizeof (*mem) == 2) \
- __asm __volatile (lock "incw %w0" \
- : "=m" (*mem) \
- : "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (sizeof (*mem) == 4) \
- __asm __volatile (lock "incl %0" \
- : "=m" (*mem) \
- : "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (__HAVE_64B_ATOMICS) \
- __asm __volatile (lock "incq %q0" \
- : "=m" (*mem) \
- : "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else \
- do_add_val_64_acq (pfx, mem, 1); \
- } while (0)
-
-#define atomic_increment(mem) __arch_increment_body (LOCK_PREFIX, __arch, mem)
-
-#define __arch_increment_cprefix \
- "cmpl $0, %%" SEG_REG ":%P2\n\tje 0f\n\tlock\n0:\t"
-
-#define catomic_increment(mem) \
- __arch_increment_body (__arch_increment_cprefix, __arch_c, mem)
-
-
-#define atomic_increment_and_test(mem) \
- ({ _Bool __result; \
- if (sizeof (*mem) == 1) \
- __asm __volatile (LOCK_PREFIX "incb %b0" \
- : "=m" (*mem), "=@cce" (__result) \
- : "m" (*mem)); \
- else if (sizeof (*mem) == 2) \
- __asm __volatile (LOCK_PREFIX "incw %w0" \
- : "=m" (*mem), "=@cce" (__result) \
- : "m" (*mem)); \
- else if (sizeof (*mem) == 4) \
- __asm __volatile (LOCK_PREFIX "incl %0" \
- : "=m" (*mem), "=@cce" (__result) \
- : "m" (*mem)); \
- else if (__HAVE_64B_ATOMICS) \
- __asm __volatile (LOCK_PREFIX "incq %q0" \
- : "=m" (*mem), "=@cce" (__result) \
- : "m" (*mem)); \
- else \
- __atomic_link_error (); \
- __result; })
-
-
#define __arch_decrement_body(lock, pfx, mem) \
do { \
if (sizeof (*mem) == 1) \
@@ -387,150 +172,12 @@
do_add_val_64_acq (pfx, mem, -1); \
} while (0)
-#define atomic_decrement(mem) __arch_decrement_body (LOCK_PREFIX, __arch, mem)
-
#define __arch_decrement_cprefix \
"cmpl $0, %%" SEG_REG ":%P2\n\tje 0f\n\tlock\n0:\t"
#define catomic_decrement(mem) \
__arch_decrement_body (__arch_decrement_cprefix, __arch_c, mem)
-
-#define atomic_decrement_and_test(mem) \
- ({ _Bool __result; \
- if (sizeof (*mem) == 1) \
- __asm __volatile (LOCK_PREFIX "decb %b0" \
- : "=m" (*mem), "=@cce" (__result) \
- : "m" (*mem)); \
- else if (sizeof (*mem) == 2) \
- __asm __volatile (LOCK_PREFIX "decw %w0" \
- : "=m" (*mem), "=@cce" (__result) \
- : "m" (*mem)); \
- else if (sizeof (*mem) == 4) \
- __asm __volatile (LOCK_PREFIX "decl %0" \
- : "=m" (*mem), "=@cce" (__result) \
- : "m" (*mem)); \
- else \
- __asm __volatile (LOCK_PREFIX "decq %q0" \
- : "=m" (*mem), "=@cce" (__result) \
- : "m" (*mem)); \
- __result; })
-
-
-#define atomic_bit_set(mem, bit) \
- do { \
- if (sizeof (*mem) == 1) \
- __asm __volatile (LOCK_PREFIX "orb %b2, %0" \
- : "=m" (*mem) \
- : "m" (*mem), IBR_CONSTRAINT (1L << (bit))); \
- else if (sizeof (*mem) == 2) \
- __asm __volatile (LOCK_PREFIX "orw %w2, %0" \
- : "=m" (*mem) \
- : "m" (*mem), "ir" (1L << (bit))); \
- else if (sizeof (*mem) == 4) \
- __asm __volatile (LOCK_PREFIX "orl %2, %0" \
- : "=m" (*mem) \
- : "m" (*mem), "ir" (1L << (bit))); \
- else if (__builtin_constant_p (bit) && (bit) < 32) \
- __asm __volatile (LOCK_PREFIX "orq %2, %0" \
- : "=m" (*mem) \
- : "m" (*mem), "i" (1L << (bit))); \
- else if (__HAVE_64B_ATOMICS) \
- __asm __volatile (LOCK_PREFIX "orq %q2, %0" \
- : "=m" (*mem) \
- : "m" (*mem), "r" (1UL << (bit))); \
- else \
- __atomic_link_error (); \
- } while (0)
-
-
-#define atomic_bit_test_set(mem, bit) \
- ({ _Bool __result; \
- if (sizeof (*mem) == 1) \
- __asm __volatile (LOCK_PREFIX "btsb %3, %1" \
- : "=@ccc" (__result), "=m" (*mem) \
- : "m" (*mem), IBR_CONSTRAINT (bit)); \
- else if (sizeof (*mem) == 2) \
- __asm __volatile (LOCK_PREFIX "btsw %3, %1" \
- : "=@ccc" (__result), "=m" (*mem) \
- : "m" (*mem), "ir" (bit)); \
- else if (sizeof (*mem) == 4) \
- __asm __volatile (LOCK_PREFIX "btsl %3, %1" \
- : "=@ccc" (__result), "=m" (*mem) \
- : "m" (*mem), "ir" (bit)); \
- else if (__HAVE_64B_ATOMICS) \
- __asm __volatile (LOCK_PREFIX "btsq %3, %1" \
- : "=@ccc" (__result), "=m" (*mem) \
- : "m" (*mem), "ir" (bit)); \
- else \
- __atomic_link_error (); \
- __result; })
-
-
-#define __arch_and_body(lock, mem, mask) \
- do { \
- if (sizeof (*mem) == 1) \
- __asm __volatile (lock "andb %b1, %0" \
- : "=m" (*mem) \
- : IBR_CONSTRAINT (mask), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (sizeof (*mem) == 2) \
- __asm __volatile (lock "andw %w1, %0" \
- : "=m" (*mem) \
- : "ir" (mask), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (sizeof (*mem) == 4) \
- __asm __volatile (lock "andl %1, %0" \
- : "=m" (*mem) \
- : "ir" (mask), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (__HAVE_64B_ATOMICS) \
- __asm __volatile (lock "andq %q1, %0" \
- : "=m" (*mem) \
- : "ir" (mask), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else \
- __atomic_link_error (); \
- } while (0)
-
-#define __arch_cprefix \
- "cmpl $0, %%" SEG_REG ":%P3\n\tje 0f\n\tlock\n0:\t"
-
-#define atomic_and(mem, mask) __arch_and_body (LOCK_PREFIX, mem, mask)
-
-#define catomic_and(mem, mask) __arch_and_body (__arch_cprefix, mem, mask)
-
-
-#define __arch_or_body(lock, mem, mask) \
- do { \
- if (sizeof (*mem) == 1) \
- __asm __volatile (lock "orb %b1, %0" \
- : "=m" (*mem) \
- : IBR_CONSTRAINT (mask), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (sizeof (*mem) == 2) \
- __asm __volatile (lock "orw %w1, %0" \
- : "=m" (*mem) \
- : "ir" (mask), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (sizeof (*mem) == 4) \
- __asm __volatile (lock "orl %1, %0" \
- : "=m" (*mem) \
- : "ir" (mask), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else if (__HAVE_64B_ATOMICS) \
- __asm __volatile (lock "orq %q1, %0" \
- : "=m" (*mem) \
- : "ir" (mask), "m" (*mem), \
- "i" (offsetof (tcbhead_t, multiple_threads))); \
- else \
- __atomic_link_error (); \
- } while (0)
-
-#define atomic_or(mem, mask) __arch_or_body (LOCK_PREFIX, mem, mask)
-
-#define catomic_or(mem, mask) __arch_or_body (__arch_cprefix, mem, mask)
-
/* We don't use mfence because it is supposedly slower due to having to
provide stronger guarantees (e.g., regarding self-modifying code). */
#define atomic_full_barrier() \
--
2.51.0
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