diff --git a/llvm/lib/Target/PowerPC/PPCInstrVSX.td b/llvm/lib/Target/PowerPC/PPCInstrVSX.td
index 136a53e66d62e..2e45d731c9531 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrVSX.td
+++ b/llvm/lib/Target/PowerPC/PPCInstrVSX.td
@@ -4647,20 +4647,24 @@ def : InstAlias<"xvmovdp $XT, $XB",
 def : InstAlias<"xvmovsp $XT, $XB",
                 (XVCPSGNSP vsrc:$XT, vsrc:$XB, vsrc:$XB)>;
 
-def : InstAlias<"xxspltd $XT, $XB, 0",
-                (XXPERMDI vsrc:$XT, vsrc:$XB, vsrc:$XB, 0)>;
-def : InstAlias<"xxspltd $XT, $XB, 1",
-                (XXPERMDI vsrc:$XT, vsrc:$XB, vsrc:$XB, 3)>;
+// Certain versions of the AIX assembler may missassemble these mnemonics.
+let Predicates = [ModernAs] in {
+  def : InstAlias<"xxspltd $XT, $XB, 0",
+                  (XXPERMDI vsrc:$XT, vsrc:$XB, vsrc:$XB, 0)>;
+  def : InstAlias<"xxspltd $XT, $XB, 1",
+                  (XXPERMDI vsrc:$XT, vsrc:$XB, vsrc:$XB, 3)>;
+  def : InstAlias<"xxspltd $XT, $XB, 0",
+                  (XXPERMDIs vsrc:$XT, vsfrc:$XB, 0)>;
+  def : InstAlias<"xxspltd $XT, $XB, 1",
+                  (XXPERMDIs vsrc:$XT, vsfrc:$XB, 3)>;
+}
+
 def : InstAlias<"xxmrghd $XT, $XA, $XB",
                 (XXPERMDI vsrc:$XT, vsrc:$XA, vsrc:$XB, 0)>;
 def : InstAlias<"xxmrgld $XT, $XA, $XB",
                 (XXPERMDI vsrc:$XT, vsrc:$XA, vsrc:$XB, 3)>;
 def : InstAlias<"xxswapd $XT, $XB",
                 (XXPERMDI vsrc:$XT, vsrc:$XB, vsrc:$XB, 2)>;
-def : InstAlias<"xxspltd $XT, $XB, 0",
-                (XXPERMDIs vsrc:$XT, vsfrc:$XB, 0)>;
-def : InstAlias<"xxspltd $XT, $XB, 1",
-                (XXPERMDIs vsrc:$XT, vsfrc:$XB, 3)>;
 def : InstAlias<"xxswapd $XT, $XB",
                 (XXPERMDIs vsrc:$XT, vsfrc:$XB, 2)>;
 def : InstAlias<"mfvrd $rA, $XT",
diff --git a/llvm/test/CodeGen/PowerPC/xxpermdi_mnemonics.s b/llvm/test/CodeGen/PowerPC/xxpermdi_mnemonics.s
new file mode 100644
index 0000000000000..ec2e2646de8fd
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/xxpermdi_mnemonics.s
@@ -0,0 +1,53 @@
+; RUN: llc -mtriple powerpc64-ibm-aix-xcoff -mcpu=pwr8 --vec-extabi < %s | FileCheck --check-prefixes=CHECK,OLD %s
+; RUN: llc -mtriple powerpc-ibm-aix-xcoff -mcpu=pwr8 --vec-extabi < %s | FileCheck --check-prefixes=CHECK,OLD %s
+
+; RUN: llc -mtriple powerpc64-unknown-linux-gnu -mcpu=pwr8 < %s | FileCheck --check-prefixes=CHECK,MODERN  %s
+; RUN: llc -mtriple powerpc64-ibm-aix-xcoff -mcpu=pwr8 -mattr=+modern-aix-as --vec-extabi < %s | FileCheck --check-prefixes=CHECK,MODERN %s
+; RUN: llc -mtriple powerpc-ibm-aix-xcoff -mcpu=pwr8 -mattr=+modern-aix-as --vec-extabi < %s | FileCheck --check-prefixes=CHECK,MODERN %s
+
+define <2 x double> @splat1(<2 x double> %A, <2 x double> %B) {
+entry:
+  %0 = shufflevector <2 x double> %B, <2 x double> undef, <2 x i32> <i32 0, i32 0>
+  ret <2 x double> %0
+}
+
+; CHECK-LABEL: splat1
+; OLD:    xxmrghd 34, 35, 35
+; MODERN: xxspltd 34, 35, 0
+
+define <2 x double> @splat2(<2 x double> %A, <2 x double> %B) {
+entry:
+  %0 = shufflevector <2 x double> %B, <2 x double> undef, <2 x i32> <i32 1, i32 1>
+  ret <2 x double> %0
+}
+
+; CHECK-LABEL: splat2
+; OLD:    xxmrgld 34, 35, 35
+; MODERN: xxspltd 34, 35, 1
+
+define <2 x double> @swap(<2 x double> %A, <2 x double> %B) {
+entry:
+  %0 = shufflevector <2 x double> %B, <2 x double> undef, <2 x i32> <i32 1, i32 0>
+  ret <2 x double> %0
+}
+
+; CHECK-LABEL: swap
+; CHECK: xxswapd 34, 35
+
+define <2 x double> @mergehi(<2 x double> %A, <2 x double> %B) {
+entry:
+  %0 = shufflevector <2 x double> %A, <2 x double> %B, <2 x i32> <i32 0, i32 2>
+  ret <2 x double> %0
+}
+
+; CHECK-LABEL: mergehi
+; CHECK: xxmrghd 34, 34, 35
+
+define <2 x double> @mergelo(<2 x double> %A, <2 x double> %B) {
+entry:
+  %0 = shufflevector <2 x double> %A, <2 x double> %B, <2 x i32> <i32 1, i32 3>
+  ret <2 x double> %0
+}
+
+; CHECK-LABEL: mergelo
+; CHECK: xxmrgld 34, 34, 35
diff --git a/llvm/test/MC/PowerPC/modern-aix-as.s b/llvm/test/MC/PowerPC/modern-aix-as.s
index 45f88a42d7713..b36d2b625a149 100644
--- a/llvm/test/MC/PowerPC/modern-aix-as.s
+++ b/llvm/test/MC/PowerPC/modern-aix-as.s
@@ -12,5 +12,14 @@
             mtudscr 2
 # CHECK-BE: mfudscr 2                       # encoding: [0x7c,0x43,0x02,0xa6]
 # CHECK-LE: mfudscr 2                       # encoding: [0xa6,0x02,0x43,0x7c]
+# CHECK-OLD: instruction use requires an option to be enabled
             mfudscr 2
+# CHECK-BE: xxspltd 2, 3, 0                 # encoding: [0xf0,0x43,0x18,0x50]
+# CHECK-LE: xxspltd 2, 3, 0                 # encoding: [0x50,0x18,0x43,0xf0]
+# CHECK-OLD: instruction use requires an option to be enabled
+            xxspltd 2, 3, 0
 
+# CHECK-BE: xxspltd 2, 3, 1                 # encoding: [0xf0,0x43,0x1b,0x50]
+# CHECK-LE: xxspltd 2, 3, 1                 # encoding: [0x50,0x1b,0x43,0xf0]
+# CHECK-OLD: instruction use requires an option to be enabled
+            xxspltd 2, 3, 1