diff --git a/llvm/lib/CodeGen/ExpandMemCmp.cpp b/llvm/lib/CodeGen/ExpandMemCmp.cpp
--- a/llvm/lib/CodeGen/ExpandMemCmp.cpp
+++ b/llvm/lib/CodeGen/ExpandMemCmp.cpp
@@ -823,7 +823,8 @@
     }
     LibFunc Func;
     if (TLI->getLibFunc(ImmutableCallSite(CI), Func) &&
-        Func == LibFunc_memcmp && expandMemCmp(CI, TTI, TL, &DL)) {
+        (Func == LibFunc_memcmp || Func == LibFunc_bcmp) &&
+        expandMemCmp(CI, TTI, TL, &DL)) {
       return true;
     }
   }
diff --git a/llvm/test/CodeGen/X86/memcmp-optsize.ll b/llvm/test/CodeGen/X86/memcmp-optsize.ll
--- a/llvm/test/CodeGen/X86/memcmp-optsize.ll
+++ b/llvm/test/CodeGen/X86/memcmp-optsize.ll
@@ -10,6 +10,7 @@
 @.str = private constant [65 x i8] c"0123456789012345678901234567890123456789012345678901234567890123\00", align 1
 
 declare i32 @memcmp(i8*, i8*, i64)
+declare i32 @bcmp(i8*, i8*, i64)
 
 define i32 @length2(i8* %X, i8* %Y) nounwind optsize {
 ; X86-LABEL: length2:
@@ -982,3 +983,31 @@
   ret i1 %c
 }
 
+define i32 @bcmp_length2(i8* %X, i8* %Y) nounwind optsize {
+; X86-LABEL: bcmp_length2:
+; X86:       # %bb.0:
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X86-NEXT:    movl {{[0-9]+}}(%esp), %ecx
+; X86-NEXT:    movzwl (%ecx), %ecx
+; X86-NEXT:    movzwl (%eax), %edx
+; X86-NEXT:    rolw $8, %cx
+; X86-NEXT:    rolw $8, %dx
+; X86-NEXT:    movzwl %cx, %eax
+; X86-NEXT:    movzwl %dx, %ecx
+; X86-NEXT:    subl %ecx, %eax
+; X86-NEXT:    retl
+;
+; X64-LABEL: bcmp_length2:
+; X64:       # %bb.0:
+; X64-NEXT:    movzwl (%rdi), %eax
+; X64-NEXT:    movzwl (%rsi), %ecx
+; X64-NEXT:    rolw $8, %ax
+; X64-NEXT:    rolw $8, %cx
+; X64-NEXT:    movzwl %ax, %eax
+; X64-NEXT:    movzwl %cx, %ecx
+; X64-NEXT:    subl %ecx, %eax
+; X64-NEXT:    retq
+  %m = tail call i32 @bcmp(i8* %X, i8* %Y, i64 2) nounwind
+  ret i32 %m
+}
+