diff --git a/gcc/config/aarch64/aarch64-protos.h b/gcc/config/aarch64/aarch64-protos.h
index bebd1b36228..61e2ad54f88 100644
--- a/gcc/config/aarch64/aarch64-protos.h
+++ b/gcc/config/aarch64/aarch64-protos.h
@@ -787,7 +787,7 @@ bool aarch64_high_bits_all_ones_p (HOST_WIDE_INT);
 
 struct atomic_ool_names
 {
-    const char *str[5][4];
+    const char *str[5][5];
 };
 
 rtx aarch64_atomic_ool_func(machine_mode mode, rtx model_rtx,
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index d934dd67fc5..67c2f1123b4 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -19617,14 +19617,14 @@ aarch64_emit_unlikely_jump (rtx insn)
   add_reg_br_prob_note (jump, profile_probability::very_unlikely ());
 }
 
-/* We store the names of the various atomic helpers in a 5x4 array.
+/* We store the names of the various atomic helpers in a 5x5 array.
    Return the libcall function given MODE, MODEL and NAMES.  */
 
 rtx
 aarch64_atomic_ool_func(machine_mode mode, rtx model_rtx,
 			const atomic_ool_names *names)
 {
-  memmodel model = memmodel_base (INTVAL (model_rtx));
+  memmodel model = memmodel_from_int (INTVAL (model_rtx));
   int mode_idx, model_idx;
 
   switch (mode)
@@ -19664,6 +19664,11 @@ aarch64_atomic_ool_func(machine_mode mode, rtx model_rtx,
     case MEMMODEL_SEQ_CST:
       model_idx = 3;
       break;
+    case MEMMODEL_SYNC_ACQUIRE:
+    case MEMMODEL_SYNC_RELEASE:
+    case MEMMODEL_SYNC_SEQ_CST:
+      model_idx = 4;
+      break;
     default:
       gcc_unreachable ();
     }
@@ -19676,7 +19681,8 @@ aarch64_atomic_ool_func(machine_mode mode, rtx model_rtx,
   { "__aarch64_" #B #N "_relax", \
     "__aarch64_" #B #N "_acq", \
     "__aarch64_" #B #N "_rel", \
-    "__aarch64_" #B #N "_acq_rel" }
+    "__aarch64_" #B #N "_acq_rel", \
+    "__aarch64_" #B #N "_sync" }
 
 #define DEF4(B)  DEF0(B, 1), DEF0(B, 2), DEF0(B, 4), DEF0(B, 8), \
 		 { NULL, NULL, NULL, NULL }
diff --git a/gcc/testsuite/gcc.target/aarch64/sync-comp-swap-ool.c b/gcc/testsuite/gcc.target/aarch64/sync-comp-swap-ool.c
new file mode 100644
index 00000000000..372f4aa8746
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sync-comp-swap-ool.c
@@ -0,0 +1,6 @@
+/* { dg-do compile } */
+/* { dg-options "-march=armv8-a+nolse -O2 -fno-ipa-icf -moutline-atomics" } */
+
+#include "sync-comp-swap.x"
+
+/* { dg-final { scan-assembler-times "bl.*__aarch64_cas4_sync" 1 } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/sync-op-acquire-ool.c b/gcc/testsuite/gcc.target/aarch64/sync-op-acquire-ool.c
new file mode 100644
index 00000000000..95d9c56b5e1
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sync-op-acquire-ool.c
@@ -0,0 +1,6 @@
+/* { dg-do compile } */
+/* { dg-options "-march=armv8-a+nolse -O2 -moutline-atomics" } */
+
+#include "sync-op-acquire.x"
+
+/* { dg-final { scan-assembler-times "bl.*__aarch64_swp4_sync" 1 } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/sync-op-full-ool.c b/gcc/testsuite/gcc.target/aarch64/sync-op-full-ool.c
new file mode 100644
index 00000000000..2f3881d9755
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sync-op-full-ool.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-march=armv8-a+nolse -O2 -moutline-atomics" } */
+
+#include "sync-op-full.x"
+
+/* { dg-final { scan-assembler-times "bl.*__aarch64_ldadd4_sync" 1 } } */
+/* { dg-final { scan-assembler-times "bl.*__aarch64_ldclr4_sync" 1 } } */
+/* { dg-final { scan-assembler-times "bl.*__aarch64_ldeor4_sync" 1 } } */
+/* { dg-final { scan-assembler-times "bl.*__aarch64_ldset4_sync" 1 } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/target_attr_20.c b/gcc/testsuite/gcc.target/aarch64/target_attr_20.c
index 509fb039e84..c9454fc420b 100644
--- a/gcc/testsuite/gcc.target/aarch64/target_attr_20.c
+++ b/gcc/testsuite/gcc.target/aarch64/target_attr_20.c
@@ -24,4 +24,4 @@ bar (void)
     }
 }
 
-/* { dg-final { scan-assembler-not "bl.*__aarch64_cas2_acq_rel" } } */
+/* { dg-final { scan-assembler-not "bl.*__aarch64_cas2_sync" } } */
diff --git a/gcc/testsuite/gcc.target/aarch64/target_attr_21.c b/gcc/testsuite/gcc.target/aarch64/target_attr_21.c
index acace4c8f2a..b8e56223b02 100644
--- a/gcc/testsuite/gcc.target/aarch64/target_attr_21.c
+++ b/gcc/testsuite/gcc.target/aarch64/target_attr_21.c
@@ -24,4 +24,4 @@ bar (void)
     }
 }
 
-/* { dg-final { scan-assembler-times "bl.*__aarch64_cas2_acq_rel" 1 } } */
+/* { dg-final { scan-assembler-times "bl.*__aarch64_cas2_sync" 1 } } */
diff --git a/libgcc/config/aarch64/lse.S b/libgcc/config/aarch64/lse.S
index c8fbfbce4fd..67a1108786f 100644
--- a/libgcc/config/aarch64/lse.S
+++ b/libgcc/config/aarch64/lse.S
@@ -87,24 +87,44 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 # define L
 # define M     0x000000
 # define N     0x000000
+# define BARRIER
 #elif MODEL == 2
 # define SUFF  _acq
 # define A     a
 # define L
 # define M     0x400000
 # define N     0x800000
+# define BARRIER
 #elif MODEL == 3
 # define SUFF  _rel
 # define A
 # define L     l
 # define M     0x008000
 # define N     0x400000
+# define BARRIER
 #elif MODEL == 4
 # define SUFF  _acq_rel
 # define A     a
 # define L     l
 # define M     0x408000
 # define N     0xc00000
+# define BARRIER
+#elif MODEL == 5
+# define SUFF  _sync
+#ifdef L_swp
+/* swp has _acq semantics.  */
+#  define A    a
+#  define L
+#  define M    0x400000
+#  define N    0x800000
+#else
+/* All other _sync functions have _seq semantics.  */
+#  define A    a
+#  define L    l
+#  define M    0x408000
+#  define N    0xc00000
+#endif
+# define BARRIER dmb		ish
 #else
 # error
 #endif
@@ -127,7 +147,12 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #endif
 
 #define NAME(BASE)		glue4(__aarch64_, BASE, SIZE, SUFF)
-#define LDXR			glue4(ld, A, xr, S)
+#if MODEL == 5
+/* Drop A for _sync functions.  */
+# define LDXR			glue3(ld, xr, S)
+#else
+# define LDXR			glue4(ld, A, xr, S)
+#endif
 #define STXR			glue4(st, L, xr, S)
 
 /* Temporary registers used.  Other than these, only the return value
@@ -183,10 +208,16 @@ STARTFN	NAME(cas)
 	bne		1f
 	STXR		w(tmp1), s(1), [x2]
 	cbnz		w(tmp1), 0b
-1:	ret
+1:	BARRIER
+	ret
 
 #else
-#define LDXP	glue3(ld, A, xp)
+#if MODEL == 5
+/* Drop A for _sync functions.  */
+# define LDXP	glue2(ld, xp)
+#else
+# define LDXP	glue3(ld, A, xp)
+#endif
 #define STXP	glue3(st, L, xp)
 #ifdef HAVE_AS_LSE
 # define CASP	glue3(casp, A, L)	x0, x1, x2, x3, [x4]
@@ -205,7 +236,8 @@ STARTFN	NAME(cas)
 	bne		1f
 	STXP		w(tmp2), x2, x3, [x4]
 	cbnz		w(tmp2), 0b
-1:	ret
+1:	BARRIER
+	ret
 
 #endif
 
@@ -229,6 +261,7 @@ STARTFN	NAME(swp)
 0:	LDXR		s(0), [x1]
 	STXR		w(tmp1), s(tmp0), [x1]
 	cbnz		w(tmp1), 0b
+	BARRIER
 	ret
 
 ENDFN	NAME(swp)
@@ -273,6 +306,7 @@ STARTFN	NAME(LDNM)
 	OP		s(tmp1), s(0), s(tmp0)
 	STXR		w(tmp2), s(tmp1), [x1]
 	cbnz		w(tmp2), 0b
+	BARRIER
 	ret
 
 ENDFN	NAME(LDNM)
diff --git a/libgcc/config/aarch64/t-lse b/libgcc/config/aarch64/t-lse
index c41f0508372..e3093724dc0 100644
--- a/libgcc/config/aarch64/t-lse
+++ b/libgcc/config/aarch64/t-lse
@@ -18,13 +18,13 @@
 # along with GCC; see the file COPYING3.  If not see
 # <http://www.gnu.org/licenses/>.
 
-# Compare-and-swap has 5 sizes and 4 memory models.
+# Compare-and-swap has 5 sizes and 5 memory models.
 S0 := $(foreach s, 1 2 4 8 16, $(addsuffix _$(s), cas))
-O0 := $(foreach m, 1 2 3 4, $(addsuffix _$(m)$(objext), $(S0)))
+O0 := $(foreach m, 1 2 3 4 5, $(addsuffix _$(m)$(objext), $(S0)))
 
-# Swap, Load-and-operate have 4 sizes and 4 memory models
+# Swap, Load-and-operate have 4 sizes and 5 memory models
 S1 := $(foreach s, 1 2 4 8, $(addsuffix _$(s), swp ldadd ldclr ldeor ldset))
-O1 := $(foreach m, 1 2 3 4, $(addsuffix _$(m)$(objext), $(S1)))
+O1 := $(foreach m, 1 2 3 4 5, $(addsuffix _$(m)$(objext), $(S1)))
 
 LSE_OBJS := $(O0) $(O1)