diff --git a/llvm/lib/Target/PowerPC/PPCInstr64Bit.td b/llvm/lib/Target/PowerPC/PPCInstr64Bit.td
--- a/llvm/lib/Target/PowerPC/PPCInstr64Bit.td
+++ b/llvm/lib/Target/PowerPC/PPCInstr64Bit.td
@@ -989,9 +989,9 @@
 
 //Disable this alias on AIX for now because as does not support them.
 let Predicates = [ModernAs] in {
-  def : InstAlias<"mtudscr $Rx", (MTSPR8 3, g8rc:$Rx)>;
-  def : InstAlias<"mfudscr $Rx", (MFSPR8 g8rc:$Rx, 3)>;
-}
+
+def : InstAlias<"mtudscr $Rx", (MTSPR8 3, g8rc:$Rx)>;
+def : InstAlias<"mfudscr $Rx", (MFSPR8 g8rc:$Rx, 3)>;
 
 def : InstAlias<"mfrtcu $Rx", (MFSPR8 g8rc:$Rx, 4)>;
 def : InstAlias<"mfrtcl $Rx", (MFSPR8 g8rc:$Rx, 5)>;
@@ -1050,6 +1050,8 @@
 def : InstAlias<"mfspefscr $Rx", (MFSPR8 g8rc:$Rx, 512)>;
 def : InstAlias<"mtspefscr $Rx", (MTSPR8 512, g8rc:$Rx)>;
 
+}
+
 //===----------------------------------------------------------------------===//
 // Load/Store instructions.
 //
diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.td b/llvm/lib/Target/PowerPC/PPCInstrInfo.td
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.td
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.td
@@ -4646,6 +4646,12 @@
 
 def : InstAlias<"xnop", (XORI R0, R0, 0)>;
 
+def : InstAlias<"mtxer $Rx", (MTSPR 1, gprc:$Rx)>;
+def : InstAlias<"mfxer $Rx", (MFSPR gprc:$Rx, 1)>;
+
+//Disable this alias on AIX for now because as does not support them.
+let Predicates = [ModernAs] in {
+
 foreach BR = 0-7 in {
     def : InstAlias<"mfbr"#BR#" $Rx",
                     (MFDCR gprc:$Rx, !add(BR, 0x80))>,
@@ -4657,15 +4663,8 @@
 
 def : InstAlias<"mtmsrd $RS", (MTMSRD gprc:$RS, 0)>;
 def : InstAlias<"mtmsr $RS", (MTMSR gprc:$RS, 0)>;
-
-def : InstAlias<"mtxer $Rx", (MTSPR 1, gprc:$Rx)>;
-def : InstAlias<"mfxer $Rx", (MFSPR gprc:$Rx, 1)>;
-
-//Disable this alias on AIX for now because as does not support them.
-let Predicates = [ModernAs] in {
 def : InstAlias<"mtudscr $Rx", (MTSPR 3, gprc:$Rx)>;
 def : InstAlias<"mfudscr $Rx", (MFSPR gprc:$Rx, 3)>;
-}
 
 def : InstAlias<"mfrtcu $Rx", (MFSPR gprc:$Rx, 4)>;
 def : InstAlias<"mfrtcl $Rx", (MFSPR gprc:$Rx, 5)>;
@@ -4795,6 +4794,7 @@
 def : InstAlias<"mticcr $Rx", (MTSPR 1019, gprc:$Rx)>, Requires<[IsPPC4xx]>;
 def : InstAlias<"mficcr $Rx", (MFSPR gprc:$Rx, 1019)>, Requires<[IsPPC4xx]>;
 
+}
 
 def : InstAlias<"tlbie $RB", (TLBIE R0, gprc:$RB)>;
 
diff --git a/llvm/test/MC/Disassembler/PowerPC/ppc64-encoding-ext.txt b/llvm/test/MC/Disassembler/PowerPC/ppc64-encoding-ext.txt
--- a/llvm/test/MC/Disassembler/PowerPC/ppc64-encoding-ext.txt
+++ b/llvm/test/MC/Disassembler/PowerPC/ppc64-encoding-ext.txt
@@ -2235,16 +2235,20 @@
 # CHECK: mfctr 2
 0x7c 0x49 0x02 0xa6
 
-# CHECK: mtuamr 2
+# MODERN: mtuamr 2
+# OLD: mtspr 13, 2
 0x7c 0x4d 0x03 0xa6
 
-# CHECK: mfuamr 2
+# MODERN: mfuamr 2
+# OLD: mfspr 2, 13
 0x7c 0x4d 0x02 0xa6
 
-# CHECK: mtppr 2
+# MODERN: mtppr 2
+# OLD: mtspr 896, 2
 0x7c 0x40 0xe3 0xa6
 
-# CHECK: mfppr 2
+# MODERN: mfppr 2
+# OLD: mfspr 2, 896
 0x7c 0x40 0xe2 0xa6
 
 # CHECK: nop