[ELF] - Added testcase for testing visibility of weak_odr symbols.

This is relative to "Bug 36166 - tools/gold/X86/comdat.ll is failing only on Debian Unstable" (PR36166).
Something changed in newer versions of gold and now together with gold-plugin
there is an issue shown in PR, symbol may get wrong visibility.

LLD works fine, but we have no testcase for the same use case, patch adds it.

Differential revision: https://reviews.llvm.org/D43193

llvm-svn: 325874

lld/test/ELF/lto/Inputs/weakodr-visibility.ll

@@ -0,0 +1,6 @@
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define weak_odr protected i32 @foo(i8* %this) {
+  ret i32 42
+}

lld/test/ELF/lto/weakodr-visibility.ll

@@ -0,0 +1,40 @@
+; REQUIRES: x86
+; RUN: llvm-as %s -o %t1.o
+; RUN: llvm-as %p/Inputs/weakodr-visibility.ll -o %t2.o
+
+; Testcase checks we keep desired visibility of weak 
+; symbol in a library even if select different definition.
+; We change the order of input files in command line and
+; check that linker selects different symbol definitions,
+; but keeps `protected` visibility.
+
+; RUN: ld.lld %t1.o %t2.o -o %t.so -shared
+; RUN: llvm-readobj -t %t.so | FileCheck %s
+; RUN: llvm-objdump -d %t.so | FileCheck %s --check-prefix=FIRST
+; CHECK:       Symbol {
+; CHECK:        Name: foo
+; CHECK-NEXT:   Value:
+; CHECK-NEXT:   Size:
+; CHECK-NEXT:   Binding: Weak
+; CHECK-NEXT:   Type: Function
+; CHECK-NEXT:   Other [
+; CHECK-NEXT:     STV_PROTECTED
+; CHECK-NEXT:   ]
+; CHECK-NEXT:   Section:
+; CHECK-NEXT: }
+; FIRST:      foo:
+; FIRST-NEXT:   movl    $41, %eax
+
+; Now swap the files order.
+; RUN: ld.lld %t2.o %t1.o -o %t.so -shared
+; RUN: llvm-readobj -t %t.so | FileCheck %s
+; RUN: llvm-objdump -d %t.so | FileCheck %s --check-prefix=SECOND
+; SECOND:      foo:
+; SECOND-NEXT:   movl    $42, %eax
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define weak_odr i32 @foo(i8* %this) {
+  ret i32 41
+}