Index: llvm/trunk/lib/Target/ARM/ARMInstrInfo.td
===================================================================
--- llvm/trunk/lib/Target/ARM/ARMInstrInfo.td
+++ llvm/trunk/lib/Target/ARM/ARMInstrInfo.td
@@ -5595,13 +5595,13 @@
 def : MnemonicAlias<"stmia", "stm">;
 def : MnemonicAlias<"stmea", "stm">;
 
-// PKHBT/PKHTB with default shift amount. PKHTB is equivalent to PKHBT when the
-// shift amount is zero (i.e., unspecified).
+// PKHBT/PKHTB with default shift amount. PKHTB is equivalent to PKHBT with the
+// input operands swapped when the shift amount is zero (i.e., unspecified).
 def : InstAlias<"pkhbt${p} $Rd, $Rn, $Rm",
                 (PKHBT GPRnopc:$Rd, GPRnopc:$Rn, GPRnopc:$Rm, 0, pred:$p)>,
         Requires<[IsARM, HasV6]>;
 def : InstAlias<"pkhtb${p} $Rd, $Rn, $Rm",
-                (PKHBT GPRnopc:$Rd, GPRnopc:$Rn, GPRnopc:$Rm, 0, pred:$p)>,
+                (PKHBT GPRnopc:$Rd, GPRnopc:$Rm, GPRnopc:$Rn, 0, pred:$p)>,
         Requires<[IsARM, HasV6]>;
 
 // PUSH/POP aliases for STM/LDM
Index: llvm/trunk/lib/Target/ARM/ARMInstrThumb2.td
===================================================================
--- llvm/trunk/lib/Target/ARM/ARMInstrThumb2.td
+++ llvm/trunk/lib/Target/ARM/ARMInstrThumb2.td
@@ -4557,13 +4557,13 @@
 def : t2InstAlias<"mvn${s}${p} $Rd, $ShiftedRm",
            (t2MVNs rGPR:$Rd, t2_so_reg:$ShiftedRm, pred:$p, cc_out:$s)>;
 
-// PKHBT/PKHTB with default shift amount. PKHTB is equivalent to PKHBT when the
-// shift amount is zero (i.e., unspecified).
+// PKHBT/PKHTB with default shift amount. PKHTB is equivalent to PKHBT with the
+// input operands swapped when the shift amount is zero (i.e., unspecified).
 def : InstAlias<"pkhbt${p} $Rd, $Rn, $Rm",
                 (t2PKHBT rGPR:$Rd, rGPR:$Rn, rGPR:$Rm, 0, pred:$p)>,
             Requires<[HasT2ExtractPack, IsThumb2]>;
 def : InstAlias<"pkhtb${p} $Rd, $Rn, $Rm",
-                (t2PKHBT rGPR:$Rd, rGPR:$Rn, rGPR:$Rm, 0, pred:$p)>,
+                (t2PKHBT rGPR:$Rd, rGPR:$Rm, rGPR:$Rn, 0, pred:$p)>,
             Requires<[HasT2ExtractPack, IsThumb2]>;
 
 // PUSH/POP aliases for STM/LDM
Index: llvm/trunk/test/MC/ARM/basic-arm-instructions.s
===================================================================
--- llvm/trunk/test/MC/ARM/basic-arm-instructions.s
+++ llvm/trunk/test/MC/ARM/basic-arm-instructions.s
@@ -1749,7 +1749,7 @@
 @ CHECK: pkhbt	r2, r2, r3              @ encoding: [0x13,0x20,0x82,0xe6]
 @ CHECK: pkhbt	r2, r2, r3, lsl #15     @ encoding: [0x93,0x27,0x82,0xe6]
 
-@ CHECK: pkhbt	r2, r2, r3              @ encoding: [0x13,0x20,0x82,0xe6]
+@ CHECK: pkhbt	r2, r3, r2              @ encoding: [0x12,0x20,0x83,0xe6]
 @ CHECK: pkhtb	r2, r2, r3, asr #31     @ encoding: [0xd3,0x2f,0x82,0xe6]
 @ CHECK: pkhtb	r2, r2, r3, asr #15     @ encoding: [0xd3,0x27,0x82,0xe6]
 
Index: llvm/trunk/test/MC/ARM/basic-thumb2-instructions.s
===================================================================
--- llvm/trunk/test/MC/ARM/basic-thumb2-instructions.s
+++ llvm/trunk/test/MC/ARM/basic-thumb2-instructions.s
@@ -1731,7 +1731,7 @@
 @ CHECK: pkhbt	r2, r2, r3              @ encoding: [0xc2,0xea,0x03,0x02]
 @ CHECK: pkhbt	r2, r2, r3, lsl #15     @ encoding: [0xc2,0xea,0xc3,0x32]
 
-@ CHECK: pkhbt	r2, r2, r3              @ encoding: [0xc2,0xea,0x03,0x02]
+@ CHECK: pkhbt	r2, r3, r2              @ encoding: [0xc3,0xea,0x02,0x02]
 @ CHECK: pkhtb	r2, r2, r3, asr #31     @ encoding: [0xc2,0xea,0xe3,0x72]
 @ CHECK: pkhtb	r2, r2, r3, asr #15     @ encoding: [0xc2,0xea,0xe3,0x32]