test: Make a start on a test suite for libLTO.

This works in a similar way to the gold plugin tests. We search for a compatible
linker on $PATH and use it to run tests against our just-built libLTO. To start
with, test the just added opt level functionality.

Differential Revision: http://reviews.llvm.org/D8472

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232785 91177308-0d34-0410-b5e6-96231b3b80d8

test/tools/lto/opt-level.ll

@@ -0,0 +1,20 @@
+; RUN: llvm-as %s -o %t.o
+; RUN: env DYLD_LIBRARY_PATH=%llvmshlibdir %ld64 -arch x86_64 -dylib -mllvm -O0 -o %t.dylib %t.o
+; RUN: llvm-nm -no-llvm-bc %t.dylib | FileCheck --check-prefix=CHECK-O0 %s
+; RUN: env DYLD_LIBRARY_PATH=%llvmshlibdir %ld64 -arch x86_64 -dylib -mllvm -O2 -o %t.dylib %t.o
+; RUN: llvm-nm -no-llvm-bc %t.dylib | FileCheck --check-prefix=CHECK-O2 %s
+
+target triple = "x86_64-apple-macosx10.8.0"
+
+; CHECK-O0: t _f1
+; CHECK-O2-NOT: _f1
+define internal void @f1() {
+  ret void
+}
+
+; CHECK-O0: T _f2
+; CHECK-O2: T _f2
+define void @f2() {
+  call void @f1()
+  ret void
+}