Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -36816,12 +36816,14 @@
     if (Size == 1) Size = 8;
     unsigned DestReg = getX86SubSuperRegisterOrZero(Res.first, Size);
     if (DestReg > 0) {
-      Res.first = DestReg;
-      Res.second = Size == 8 ? &X86::GR8RegClass
-                 : Size == 16 ? &X86::GR16RegClass
-                 : Size == 32 ? &X86::GR32RegClass
-                 : &X86::GR64RegClass;
-      assert(Res.second->contains(Res.first) && "Register in register class");
+      bool is64Bit = Subtarget.is64Bit();
+      const TargetRegisterClass *RC =
+          Size == 8 ? (is64Bit ? &X86::GR8RegClass : &X86::GR8_NOREXRegClass)
+        : Size == 16 ? (is64Bit ? &X86::GR16RegClass : &X86::GR16_NOREXRegClass)
+        : Size == 32 ? (is64Bit ? &X86::GR32RegClass : &X86::GR32_NOREXRegClass)
+        : &X86::GR64RegClass;
+      if (RC->contains(DestReg))
+        Res = std::make_pair(DestReg, RC);
     } else {
       // No register found/type mismatch.
       Res.first = 0;
Index: test/CodeGen/X86/pr29061.ll
===================================================================
--- test/CodeGen/X86/pr29061.ll
+++ test/CodeGen/X86/pr29061.ll
@@ -0,0 +1,44 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple i386-unknown-linux-gnu < %s | FileCheck %s
+
+; Previously, a reference to SIL/DIL was being emitted
+; but those aren't available unless on a 64bit mode
+
+define void @t1(i8 signext %c) {
+; CHECK-LABEL: t1:
+; CHECK:       # BB#0: # %entry
+; CHECK-NEXT:    pushl %edi
+; CHECK-NEXT:  .Lcfi0:
+; CHECK-NEXT:    .cfi_def_cfa_offset 8
+; CHECK-NEXT:  .Lcfi1:
+; CHECK-NEXT:    .cfi_offset %edi, -8
+; CHECK-NEXT:    movzbl {{[0-9]+}}(%esp), %edi
+; CHECK-NEXT:    # kill: %DI<def> %DI<kill> %EDI<kill>
+; CHECK-NEXT:    #APP
+; CHECK-NEXT:    #NO_APP
+; CHECK-NEXT:    popl %edi
+; CHECK-NEXT:    retl
+entry:
+  tail call void asm sideeffect "", "{di},~{dirflag},~{fpsr},~{flags}"(i8 %c)
+  ret void
+}
+
+define void @t2(i8 signext %c) {
+; CHECK-LABEL: t2:
+; CHECK:       # BB#0: # %entry
+; CHECK-NEXT:    pushl %esi
+; CHECK-NEXT:  .Lcfi2:
+; CHECK-NEXT:    .cfi_def_cfa_offset 8
+; CHECK-NEXT:  .Lcfi3:
+; CHECK-NEXT:    .cfi_offset %esi, -8
+; CHECK-NEXT:    movzbl {{[0-9]+}}(%esp), %esi
+; CHECK-NEXT:    # kill: %SI<def> %SI<kill> %ESI<kill>
+; CHECK-NEXT:    #APP
+; CHECK-NEXT:    #NO_APP
+; CHECK-NEXT:    popl %esi
+; CHECK-NEXT:    retl
+entry:
+  tail call void asm sideeffect "", "{si},~{dirflag},~{fpsr},~{flags}"(i8 %c)
+  ret void
+}
+