Add bitcodelibfuncs flag to lto2 (not hooked up)

Author: mysterymath

llvm/test/LTO/Resolution/X86/libcall-external-bitcode.ll

@@ -0,0 +1,20 @@
+; RUN: opt %s -o %t -module-summary -mtriple x86_64-unknown-linux-musl
+; RUN: llvm-lto2 run -o %t2 \
+; RUN:   -r %t,foo,plx \
+; RUN:   -r %t,memcmp,x \
+; RUN:   -r %t,bcmp,pl --bitcode-libfuncs=bcmp %t -save-temps
+; RUN: llvm-dis %t2.1.4.opt.bc -o - | FileCheck %s
+
+define i1 @foo(ptr %0, ptr %1, i64 %2) {
+  ; CHECK-LABEL: define{{.*}}i1 @foo
+  ; CHECK-NEXT: %cmp = {{.*}}call i32 @memcmp
+  ; CHECK-NEXT: %eq = icmp eq i32 %bcmp, 0
+  ; CHECK-NEXT: ret i1 %eq
+
+  %cmp = call i32 @memcmp(ptr %0, ptr %1, i64 %2)
+  %eq = icmp eq i32 %cmp, 0
+  ret i1 %eq
+}
+
+declare i32 @memcmp(ptr, ptr, i64)
+declare i32 @bcmp(ptr, ptr, i64)

llvm/tools/llvm-lto2/llvm-lto2.cpp

@@ -232,6 +232,10 @@ static cl::opt<bool>
     AllVtablesHaveTypeInfos("all-vtables-have-type-infos", cl::Hidden,
                             cl::desc("All vtables have type infos"));
 
+static cl::list<std::string>
+    BitcodeLibFuncs("bitcode-libfuncs", cl::Hidden,
+                    cl::desc("set of libfuncs implemented in bitcode"));
+
 static void check(Error E, std::string Msg) {
   if (!E)
     return;