diff --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index 3bb5d3cb4d09d..c2eea836fb14f 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -12529,26 +12529,19 @@ multiclass STOPregister<string asm, string instr> {
                     !cast<Instruction>(instr # "X")>;
 }
 
+let Predicates = [HasLSUI] in
 class BaseSTOPregisterLSUI<string asm, RegisterClass OP, Register Reg,
                         Instruction inst> :
-      InstAlias<asm # "\t$Rs, [$Rn]", (inst Reg, OP:$Rs, GPR64sp:$Rn)>;
+      InstAlias<asm # "\t$Rs, [$Rn]", (inst Reg, OP:$Rs, GPR64sp:$Rn), 0>;
 
 multiclass STOPregisterLSUI<string asm, string instr> {
-  def : BaseSTOPregisterLSUI<asm # "a",        GPR32, WZR,
-                    !cast<Instruction>(instr # "W")>;
-  def : BaseSTOPregisterLSUI<asm # "a",        GPR64, XZR,
-                    !cast<Instruction>(instr # "X")>;
-  def : BaseSTOPregisterLSUI<asm # "l",        GPR32, WZR,
-                    !cast<Instruction>(instr # "W")>;
-  def : BaseSTOPregisterLSUI<asm # "l",        GPR64, XZR,
-                    !cast<Instruction>(instr # "X")>;
-  def : BaseSTOPregisterLSUI<asm # "al",        GPR32, WZR,
-                    !cast<Instruction>(instr # "W")>;
-  def : BaseSTOPregisterLSUI<asm # "al",        GPR64, XZR,
-                    !cast<Instruction>(instr # "X")>;
-  def : BaseSTOPregisterLSUI<asm,        GPR32, WZR,
+  def : BaseSTOPregisterLSUI<asm # "l", GPR32, WZR,
+                    !cast<Instruction>(instr # "LW")>;
+  def : BaseSTOPregisterLSUI<asm # "l", GPR64, XZR,
+                    !cast<Instruction>(instr # "LX")>;
+  def : BaseSTOPregisterLSUI<asm, GPR32, WZR,
                     !cast<Instruction>(instr # "W")>;
-  def : BaseSTOPregisterLSUI<asm,        GPR64, XZR,
+  def : BaseSTOPregisterLSUI<asm, GPR64, XZR,
                     !cast<Instruction>(instr # "X")>;
 }
 
diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.td b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
index a0928b9095fcc..58c829243adbd 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
@@ -2665,21 +2665,11 @@ defm CASLT  : CompareAndSwapUnprivileged<0b11, 0, 1, "l">;
 defm CASAT  : CompareAndSwapUnprivileged<0b11, 1, 0, "a">;
 defm CASALT : CompareAndSwapUnprivileged<0b11, 1, 1, "al">;
 
-def : MnemonicAlias<"cas", "cast">;
-def : MnemonicAlias<"casl", "caslt">;
-def : MnemonicAlias<"casa", "casat">;
-def : MnemonicAlias<"casal", "casalt">;
-
 // v9.6-a atomic CASPT
 defm CASPT   : CompareAndSwapPairUnprivileged<0b01, 0, 0, "">;
 defm CASPLT  : CompareAndSwapPairUnprivileged<0b01, 0, 1, "l">;
 defm CASPAT  : CompareAndSwapPairUnprivileged<0b01, 1, 0, "a">;
 defm CASPALT : CompareAndSwapPairUnprivileged<0b01, 1, 1, "al">;
-
-def : MnemonicAlias<"casp", "caspt">;
-def : MnemonicAlias<"caspl", "casplt">;
-def : MnemonicAlias<"caspa", "caspat">;
-def : MnemonicAlias<"caspal", "caspalt">;
 }
 
 // v8.1 atomic SWP
@@ -2694,11 +2684,6 @@ let Predicates = [HasLSUI] in {
   defm SWPTA  : SwapLSUI<1, 0, "a">;
   defm SWPTL  : SwapLSUI<0, 1, "l">;
   defm SWPTAL : SwapLSUI<1, 1, "al">;
-
-  def : MnemonicAlias<"swp", "swpt">;
-  def : MnemonicAlias<"swpa", "swpta">;
-  def : MnemonicAlias<"swpl", "swptl">;
-  def : MnemonicAlias<"swpal", "swptal">;
 }
 
 // v9.6-a unprivileged atomic LD<OP> (FEAT_LSUI)
@@ -4863,22 +4848,14 @@ let Predicates = [HasLSUI] in {
 defm LDTXRW : LoadUnprivilegedLSUI<0b10, GPR32, "ldtxr">;
 defm LDTXRX : LoadUnprivilegedLSUI<0b11, GPR64, "ldtxr">;
 
-def : MnemonicAlias<"ldxr", "ldtxr">;
-
 def LDATXRW : LoadExclusiveLSUI <0b10, 1, 1, GPR32, "ldatxr">;
 def LDATXRX : LoadExclusiveLSUI <0b11, 1, 1, GPR64, "ldatxr">;
 
-def : MnemonicAlias<"ldaxr", "ldatxr">;
-
 defm STTXRW : StoreUnprivilegedLSUI<0b10, GPR32, "sttxr">;
 defm STTXRX : StoreUnprivilegedLSUI<0b11, GPR64, "sttxr">;
 
-def : MnemonicAlias<"stxr", "sttxr">;
-
 def STLTXRW : StoreExclusiveLSUI<0b10, 0, 1, GPR32, "stltxr">;
 def STLTXRX : StoreExclusiveLSUI<0b11, 0, 1, GPR64, "stltxr">;
-
-def : MnemonicAlias<"stlxr", "stltxr">;
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/llvm/test/MC/AArch64/armv8.1a-lse.s b/llvm/test/MC/AArch64/armv8.1a-lse.s
index b5bbbe66c6ae2..eb9a30dea9e6b 100644
--- a/llvm/test/MC/AArch64/armv8.1a-lse.s
+++ b/llvm/test/MC/AArch64/armv8.1a-lse.s
@@ -7,6 +7,8 @@
 // RUN: not llvm-mc -triple aarch64-none-linux-gnu -mcpu=tsv110 -show-encoding < %s 2> %t | FileCheck %s
 // RUN: FileCheck -check-prefix=CHECK-ERROR < %t %s
 // RUN: not llvm-mc -triple aarch64-none-linux-gnu -mattr=+v8r -show-encoding < %s 2> %t | FileCheck %s
+// RUN: FileCheck -check-prefix=CHECK-ERROR < %t %s
+// RUN: not llvm-mc -triple aarch64-none-linux-gnu -mattr=+v8.1a,+lse,+lsui -show-encoding < %s 2> %t | FileCheck %s
 // RUN: FileCheck -check-prefix=CHECK-ERROR < %t %s
   .text
 
diff --git a/llvm/test/MC/AArch64/armv9.6a-lsui.s b/llvm/test/MC/AArch64/armv9.6a-lsui.s
index b48db1f9b5570..d4a5e1f980560 100644
--- a/llvm/test/MC/AArch64/armv9.6a-lsui.s
+++ b/llvm/test/MC/AArch64/armv9.6a-lsui.s
@@ -313,42 +313,16 @@ _func:
 // ERROR: instruction requires: lsui
 
   sttaddl    w0, [x2]
-// CHECK: ldtadd	w0, wzr, [x2]                   // encoding: [0x5f,0x04,0x20,0x19]
+// CHECK: ldtaddl	w0, wzr, [x2]                   // encoding: [0x5f,0x04,0x60,0x19]
 // ERROR: instruction requires: lsui
   sttaddl    w2, [sp]
-// CHECK: ldtadd	w2, wzr, [sp]                   // encoding: [0xff,0x07,0x22,0x19]
+// CHECK: ldtaddl	w2, wzr, [sp]                   // encoding: [0xff,0x07,0x62,0x19]
 // ERROR: instruction requires: lsui
   sttaddl    x0, [x2]
-// CHECK: ldtadd	x0, xzr, [x2]                   // encoding: [0x5f,0x04,0x20,0x59]
+// CHECK: ldtaddl	x0, xzr, [x2]                   // encoding: [0x5f,0x04,0x60,0x59]
 // ERROR: instruction requires: lsui
   sttaddl    x2, [sp]
-// CHECK: ldtadd	x2, xzr, [sp]                   // encoding: [0xff,0x07,0x22,0x59]
-// ERROR: instruction requires: lsui
-
-  sttadda    w0, [x2]
-// CHECK: ldtadd	w0, wzr, [x2]                   // encoding: [0x5f,0x04,0x20,0x19]
-// ERROR: instruction requires: lsui
-  sttadda    w2, [sp]
-// CHECK: ldtadd	w2, wzr, [sp]                   // encoding: [0xff,0x07,0x22,0x19]
-// ERROR: instruction requires: lsui
-  sttadda    x0, [x2]
-// CHECK: ldtadd	x0, xzr, [x2]                   // encoding: [0x5f,0x04,0x20,0x59]
-// ERROR: instruction requires: lsui
-  sttadda    x2, [sp]
-// CHECK: ldtadd	x2, xzr, [sp]                   // encoding: [0xff,0x07,0x22,0x59]
-// ERROR: instruction requires: lsui
-
-  sttaddal   w0, [x2]
-// CHECK: ldtadd	w0, wzr, [x2]                   // encoding: [0x5f,0x04,0x20,0x19]
-// ERROR: instruction requires: lsui
-  sttaddal   w2, [sp]
-// CHECK: ldtadd	w2, wzr, [sp]                   // encoding: [0xff,0x07,0x22,0x19]
-// ERROR: instruction requires: lsui
-  sttaddal   x0, [x2]
-// CHECK: ldtadd	x0, xzr, [x2]                   // encoding: [0x5f,0x04,0x20,0x59]
-// ERROR: instruction requires: lsui
-  sttaddal   x2, [sp]
-// CHECK: ldtadd	x2, xzr, [sp]                   // encoding: [0xff,0x07,0x22,0x59]
+// CHECK: ldtaddl	x2, xzr, [sp]                   // encoding: [0xff,0x07,0x62,0x59]
 // ERROR: instruction requires: lsui
 
   sttclr     w0, [x2]
@@ -362,45 +336,19 @@ _func:
 // ERROR: instruction requires: lsui
   sttclr     x2, [sp]
 // CHECK: ldtclr	x2, xzr, [sp]                   // encoding: [0xff,0x17,0x22,0x59]
-// ERROR: instruction requires: lsui
-
-  sttclra    w0, [x2]
-// CHECK: ldtclr	w0, wzr, [x2]                   // encoding: [0x5f,0x14,0x20,0x19]
-// ERROR: instruction requires: lsui
-  sttclra    w2, [sp]
-// CHECK: ldtclr	w2, wzr, [sp]                   // encoding: [0xff,0x17,0x22,0x19]
-// ERROR: instruction requires: lsui
-  sttclra    x0, [x2]
-// CHECK: ldtclr	x0, xzr, [x2]                   // encoding: [0x5f,0x14,0x20,0x59]
-// ERROR: instruction requires: lsui
-  sttclra    x2, [sp]
-// CHECK: ldtclr	x2, xzr, [sp]                   // encoding: [0xff,0x17,0x22,0x59]
 // ERROR: instruction requires: lsui
 
   sttclrl    w0, [x2]
-// CHECK: ldtclr	w0, wzr, [x2]                   // encoding: [0x5f,0x14,0x20,0x19]
+// CHECK: ldtclrl	w0, wzr, [x2]                   // encoding: [0x5f,0x14,0x60,0x19]
 // ERROR: instruction requires: lsui
   sttclrl    w2, [sp]
-// CHECK: ldtclr	w2, wzr, [sp]                   // encoding: [0xff,0x17,0x22,0x19]
+// CHECK: ldtclrl	w2, wzr, [sp]                   // encoding: [0xff,0x17,0x62,0x19]
 // ERROR: instruction requires: lsui
   sttclrl    x0, [x2]
-// CHECK: ldtclr	x0, xzr, [x2]                   // encoding: [0x5f,0x14,0x20,0x59]
+// CHECK: ldtclrl	x0, xzr, [x2]                   // encoding: [0x5f,0x14,0x60,0x59]
 // ERROR: instruction requires: lsui
   sttclrl    x2, [sp]
-// CHECK: ldtclr	x2, xzr, [sp]                   // encoding: [0xff,0x17,0x22,0x59]
-// ERROR: instruction requires: lsui
-
-  sttclral   w0, [x2]
-// CHECK: ldtclr	w0, wzr, [x2]                   // encoding: [0x5f,0x14,0x20,0x19]
-// ERROR: instruction requires: lsui
-  sttclral   x2, [sp]
-// CHECK: ldtclr	x2, xzr, [sp]                   // encoding: [0xff,0x17,0x22,0x59]
-// ERROR: instruction requires: lsui
-  sttclral   x0, [x2]
-// CHECK: ldtclr	x0, xzr, [x2]                   // encoding: [0x5f,0x14,0x20,0x59]
-// ERROR: instruction requires: lsui
-  sttclral   x2, [sp]
-// CHECK: ldtclr	x2, xzr, [sp]                   // encoding: [0xff,0x17,0x22,0x59]
+// CHECK: ldtclrl	x2, xzr, [sp]                   // encoding: [0xff,0x17,0x62,0x59]
 // ERROR: instruction requires: lsui
 
   sttset     w0, [x2]
@@ -414,45 +362,19 @@ _func:
 // ERROR: instruction requires: lsui
   sttset     x2, [sp]
 // CHECK: ldtset	x2, xzr, [sp]                   // encoding: [0xff,0x37,0x22,0x59]
-// ERROR: instruction requires: lsui
-
-  sttseta    w0, [x2]
-// CHECK: ldtset	w0, wzr, [x2]                   // encoding: [0x5f,0x34,0x20,0x19]
-// ERROR: instruction requires: lsui
-  sttseta    w2, [sp]
-// CHECK: ldtset	w2, wzr, [sp]                   // encoding: [0xff,0x37,0x22,0x19]
-// ERROR: instruction requires: lsui
-  sttseta    x0, [x2]
-// CHECK: ldtset	x0, xzr, [x2]                   // encoding: [0x5f,0x34,0x20,0x59]
-// ERROR: instruction requires: lsui
-  sttseta    x2, [sp]
-// CHECK: ldtset	x2, xzr, [sp]                   // encoding: [0xff,0x37,0x22,0x59]
 // ERROR: instruction requires: lsui
 
   sttsetl    w0, [x2]
-// CHECK: ldtset	w0, wzr, [x2]                   // encoding: [0x5f,0x34,0x20,0x19]
+// CHECK: ldtsetl	w0, wzr, [x2]                   // encoding: [0x5f,0x34,0x60,0x19]
 // ERROR: instruction requires: lsui
   sttsetl    w2, [sp]
-// CHECK: ldtset	w2, wzr, [sp]                   // encoding: [0xff,0x37,0x22,0x19]
+// CHECK: ldtsetl	w2, wzr, [sp]                   // encoding: [0xff,0x37,0x62,0x19]
 // ERROR: instruction requires: lsui
   sttsetl    x0, [x2]
-// CHECK: ldtset	x0, xzr, [x2]                   // encoding: [0x5f,0x34,0x20,0x59]
+// CHECK: ldtsetl	x0, xzr, [x2]                   // encoding: [0x5f,0x34,0x60,0x59]
 // ERROR: instruction requires: lsui
   sttsetl    x2, [sp]
-// CHECK: ldtset	x2, xzr, [sp]                   // encoding: [0xff,0x37,0x22,0x59]
-// ERROR: instruction requires: lsui
-
-  sttsetal   w0, [x2]
-// CHECK: ldtset	w0, wzr, [x2]                   // encoding: [0x5f,0x34,0x20,0x19]
-// ERROR: instruction requires: lsui
-  sttsetal   x2, [sp]
-// CHECK: ldtset	x2, xzr, [sp]                   // encoding: [0xff,0x37,0x22,0x59]
-// ERROR: instruction requires: lsui
-  sttsetal   x0, [x2]
-// CHECK: ldtset	x0, xzr, [x2]                   // encoding: [0x5f,0x34,0x20,0x59]
-// ERROR: instruction requires: lsui
-  sttsetal   x2, [sp]
-// CHECK: ldtset	x2, xzr, [sp]                   // encoding: [0xff,0x37,0x22,0x59]
+// CHECK: ldtsetl	x2, xzr, [sp]                   // encoding: [0xff,0x37,0x62,0x59]
 // ERROR: instruction requires: lsui
 
 //------------------------------------------------------------------------------