diff --git a/llvm/lib/Target/X86/X86InstrExtension.td b/llvm/lib/Target/X86/X86InstrExtension.td
index 2e1d523ea16d..e62e6b701f46 100644
--- a/llvm/lib/Target/X86/X86InstrExtension.td
+++ b/llvm/lib/Target/X86/X86InstrExtension.td
@@ -76,12 +76,12 @@ def MOVZX32rm16: I<0xB7, MRMSrcMem, (outs GR32:$dst), (ins i16mem:$src),
 // except that they use GR32_NOREX for the output operand register class
 // instead of GR32. This allows them to operate on h registers on x86-64.
 def MOVZX32_NOREXrr8 : I<0xB6, MRMSrcReg,
-                         (outs GR32_NOREX:$dst), (ins GR8:$src),
+                         (outs GR32_NOREX:$dst), (ins GR8_NOREX:$src),
                          "movz{bl|x}\t{$src, $dst|$dst, $src}",
                          []>, TB;
 let mayLoad = 1 in
 def MOVZX32_NOREXrm8 : I<0xB6, MRMSrcMem,
-                         (outs GR32_NOREX:$dst), (ins i8mem:$src),
+                         (outs GR32_NOREX:$dst), (ins i8mem_NOREX:$src),
                          "movz{bl|x}\t{$src, $dst|$dst, $src}",
                          []>, TB;
 
diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
index bad978d87471..86fb3a52724e 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -2189,9 +2189,12 @@ void X86InstrInfo::copyPhysReg(MachineBasicBlock &MBB,
     // Copying to or from a physical H register on x86-64 requires a NOREX
     // move.  Otherwise use a normal move.
     if ((isHReg(DestReg) || isHReg(SrcReg)) &&
-        TM.getSubtarget<X86Subtarget>().is64Bit())
+        TM.getSubtarget<X86Subtarget>().is64Bit()) {
       Opc = X86::MOV8rr_NOREX;
-    else
+      // Both operands must be encodable without an REX prefix.
+      assert(X86::GR8_NOREXRegClass.contains(SrcReg, DestReg) &&
+             "8-bit H register can not be copied outside GR8_NOREX");
+    } else
       Opc = X86::MOV8rr;
   } else if (X86::VR128RegClass.contains(DestReg, SrcReg))
     Opc = HasAVX ? X86::VMOVAPSrr : X86::MOVAPSrr;