diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index c1d66cb5702..91cec989469 100644
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -1913,6 +1913,9 @@ bool X86InstrInfo::copyRegToReg(MachineBasicBlock &MBB,
     else if (SrcRC->hasSuperClass(&X86::GR32RegClass) &&
              DestRC->hasSuperClass(&X86::GR32RegClass))
       CommonRC = &X86::GR32RegClass;
+    else if (SrcRC->hasSuperClass(&X86::GR8RegClass) &&
+             DestRC->hasSuperClass(&X86::GR8RegClass))
+      CommonRC = &X86::GR8RegClass;
     else
       CommonRC = 0;
   }
diff --git a/test/CodeGen/X86/crash.ll b/test/CodeGen/X86/crash.ll
index 2f27f35f0ac..a14a48baa35 100644
--- a/test/CodeGen/X86/crash.ll
+++ b/test/CodeGen/X86/crash.ll
@@ -130,3 +130,14 @@ bb14:
 bb67:
   ret void
 }
+
+; Crash when trying to copy AH to AL.
+; PR7540
+define void @copy8bitregs() nounwind {
+entry:
+  %div.i = sdiv i32 115200, 0
+  %shr8.i = lshr i32 %div.i, 8
+  %conv4.i = trunc i32 %shr8.i to i8
+  call void asm sideeffect "outb $0, ${1:w}", "{ax},N{dx},~{dirflag},~{fpsr},~{flags}"(i8 %conv4.i, i32 1017) nounwind
+  unreachable
+}