Index: llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
===================================================================
--- llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -7947,6 +7947,40 @@
       return Error (Operands[3]->getStartLoc(), "Q-register indexes must be 2 and 0 or 3 and 1");
     break;
   }
+  case ARM::UMAAL:
+  case ARM::UMLAL:
+  case ARM::UMULL:
+  case ARM::t2UMAAL:
+  case ARM::t2UMLAL:
+  case ARM::t2UMULL:
+  case ARM::SMLAL:
+  case ARM::SMLALBB:
+  case ARM::SMLALBT:
+  case ARM::SMLALD:
+  case ARM::SMLALDX:
+  case ARM::SMLALTB:
+  case ARM::SMLALTT:
+  case ARM::SMLSLD:
+  case ARM::SMLSLDX:
+  case ARM::SMULL:
+  case ARM::t2SMLAL:
+  case ARM::t2SMLALBB:
+  case ARM::t2SMLALBT:
+  case ARM::t2SMLALD:
+  case ARM::t2SMLALDX:
+  case ARM::t2SMLALTB:
+  case ARM::t2SMLALTT:
+  case ARM::t2SMLSLD:
+  case ARM::t2SMLSLDX:
+  case ARM::t2SMULL: {
+    unsigned RdHi = Inst.getOperand(0).getReg();
+    unsigned RdLo = Inst.getOperand(1).getReg();
+    if(getContext().getRegisterInfo()->isSubRegisterEq(RdHi, RdLo)) {
+      return Error(Loc,
+                   "unpredictable instruction, RdHi and RdLo must be different");
+    }
+    break;
+  }
   }
 
   return false;
Index: llvm/test/MC/ARM/equal-rdhi-rdlo-diagnostics.s
===================================================================
--- /dev/null
+++ llvm/test/MC/ARM/equal-rdhi-rdlo-diagnostics.s
@@ -0,0 +1,32 @@
+@ RUN: not llvm-mc -triple thumbv7m-eabi -mattr=+dsp < %s 2> %t
+@ RUN: FileCheck < %t %s
+@ RUN: not llvm-mc -triple armv8 -mattr=+dsp < %s 2> %t
+@ RUN: FileCheck < %t %s
+
+f:
+        smlal   r1, r1, r3, r4
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        smlalbb   r1, r1, r3, r4
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        smlalbt   r1, r1, r3, r4
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        smlaltb   r1, r1, r3, r4
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        smlaltt   r1, r1, r3, r4
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        smlald   r1, r1, r3, r4
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        smlaldx   r1, r1, r3, r4
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        smlsld  r1, r1, r3, r4
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        smlsldx  r1, r1, r3, r4
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        smull   r1, r1, r2, r3
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        umull   r1, r1, r2, r3
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        umlal   r1, r1, r2, r3
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
+        umaal   r1, r1, r2, r3
+        @ CHECK: error: unpredictable instruction, RdHi and RdLo must be different
Index: llvm/test/MC/ARM/v8_IT_manual.s
===================================================================
--- llvm/test/MC/ARM/v8_IT_manual.s
+++ llvm/test/MC/ARM/v8_IT_manual.s
@@ -6557,169 +6557,169 @@
 mlage r0, lr, r0, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r0, r0
+smullge r0, r1, r0, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r1, r0
+smullge r0, r1, r1, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r2, r0
+smullge r0, r1, r2, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r3, r0
+smullge r0, r1, r3, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r4, r0
+smullge r0, r1, r4, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r5, r0
+smullge r0, r1, r5, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r6, r0
+smullge r0, r1, r6, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r7, r0
+smullge r0, r1, r7, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r8, r0
+smullge r0, r1, r8, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r9, r0
+smullge r0, r1, r9, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r10, r0
+smullge r0, r1, r10, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r11, r0
+smullge r0, r1, r11, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, r12, r0
+smullge r0, r1, r12, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smullge r0, r0, lr, r0
+smullge r0, r1, lr, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r0, r0
+umullge r0, r1, r0, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r1, r0
+umullge r0, r1, r1, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r2, r0
+umullge r0, r1, r2, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r3, r0
+umullge r0, r1, r3, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r4, r0
+umullge r0, r1, r4, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r5, r0
+umullge r0, r1, r5, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r6, r0
+umullge r0, r1, r6, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r7, r0
+umullge r0, r1, r7, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r8, r0
+umullge r0, r1, r8, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r9, r0
+umullge r0, r1, r9, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r10, r0
+umullge r0, r1, r10, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r11, r0
+umullge r0, r1, r11, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, r12, r0
+umullge r0, r1, r12, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umullge r0, r0, lr, r0
+umullge r0, r1, lr, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r0, r0
+smlalge r0, r1, r0, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r1, r0
+smlalge r0, r1, r1, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r2, r0
+smlalge r0, r1, r2, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r3, r0
+smlalge r0, r1, r3, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r4, r0
+smlalge r0, r1, r4, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r5, r0
+smlalge r0, r1, r5, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r6, r0
+smlalge r0, r1, r6, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r7, r0
+smlalge r0, r1, r7, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r8, r0
+smlalge r0, r1, r8, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r9, r0
+smlalge r0, r1, r9, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r10, r0
+smlalge r0, r1, r10, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r11, r0
+smlalge r0, r1, r11, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, r12, r0
+smlalge r0, r1, r12, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-smlalge r0, r0, lr, r0
+smlalge r0, r1, lr, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r0, r0
+umlalge r0, r1, r0, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r1, r0
+umlalge r0, r1, r1, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r2, r0
+umlalge r0, r1, r2, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r3, r0
+umlalge r0, r1, r3, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r4, r0
+umlalge r0, r1, r4, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r5, r0
+umlalge r0, r1, r5, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r6, r0
+umlalge r0, r1, r6, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r7, r0
+umlalge r0, r1, r7, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r8, r0
+umlalge r0, r1, r8, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r9, r0
+umlalge r0, r1, r9, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r10, r0
+umlalge r0, r1, r10, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r11, r0
+umlalge r0, r1, r11, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, r12, r0
+umlalge r0, r1, r12, r0
 @ CHECK: :[[@LINE+2]]:1: warning: deprecated instruction in IT block
 it ge
-umlalge r0, r0, lr, r0
+umlalge r0, r1, lr, r0