[clang/darwin] Pass libclang_rt.profile last on linker command

[thakis]

Summary

This reverts the functional change of https://reviews.llvm.org/D35385 because
it sounds like this is no longer necessary
(https://bugs.llvm.org/show_bug.cgi?id=51135#c11) and makes clang's behavior
more uniform across platforms.

After committing this, I noticed that this is needed for correctness for profiling
builds with lld: https://bugs.llvm.org/show_bug.cgi?id=51135#c14

[thakis]

Whoops, I'm so used to sending lld changes that I put the wrong reviewers and subscribers at first. Fixed now.

[MaskRay]

LG

[thakis]

@vsk, I'll go ahead and land this. If this does cause problems for you after all (on the bug you said it should be fine), please revert :)

[vsk]

@thakis thanks for doing this, lgtm as well.

clang/lib/Driver/ToolChains/Darwin.h

enum RuntimeLinkOptions : unsigned {
     /// Link the library in even if it can't be found in the VFS.
     RLO_AlwaysLink = 1 << 0,
 
     /// Use the embedded runtime from the macho_embedded directory.
     RLO_IsEmbedded = 1 << 1,
 
     /// Emit rpaths for @executable_path as well as the resource directory.
     RLO_AddRPath = 1 << 2,
-
-    /// Link the library in before any others.
-    RLO_FirstLink = 1 << 3,
   };
 
   /// Add a runtime library to the list of items to link.
   void AddLinkRuntimeLib(const llvm::opt::ArgList &Args,
                          llvm::opt::ArgStringList &CmdArgs, StringRef Component,
                          RuntimeLinkOptions Opts = RuntimeLinkOptions(),
                          bool IsShared = false) const;
 

clang/lib/Driver/ToolChains/Darwin.cpp

void MachO::AddLinkRuntimeLib(const ArgList &Args, ArgStringList &CmdArgs,
   SmallString<128> P(Dir);
   llvm::sys::path::append(P, DarwinLibName);
 
   // For now, allow missing resource libraries to support developers who may
   // not have compiler-rt checked out or integrated into their build (unless
   // we explicitly force linking with this library).
   if ((Opts & RLO_AlwaysLink) || getVFS().exists(P)) {
     const char *LibArg = Args.MakeArgString(P);
-    if (Opts & RLO_FirstLink)
-      CmdArgs.insert(CmdArgs.begin(), LibArg);
-    else
-      CmdArgs.push_back(LibArg);
   }
 
   // Adding the rpaths might negatively interact when other rpaths are involved,
   // so we should make sure we add the rpaths last, after all user-specified
   // rpaths. This is currently true from this place, but we need to be
   // careful if this function is ever called before user's rpaths are emitted.
   if (Opts & RLO_AddRPath) {
     assert(DarwinLibName.endswith(".dylib") && "must be a dynamic library");

 }
 
 void Darwin::addProfileRTLibs(const ArgList &Args,
                               ArgStringList &CmdArgs) const {
   if (!needsProfileRT(Args) && !needsGCovInstrumentation(Args))
     return;
 
   AddLinkRuntimeLib(Args, CmdArgs, "profile",
-                    RuntimeLinkOptions(RLO_AlwaysLink | RLO_FirstLink));
+                    RuntimeLinkOptions(RLO_AlwaysLink));
 
   bool ForGCOV = needsGCovInstrumentation(Args);
 
   // If we have a symbol export directive and we're linking in the profile
   // runtime, automatically export symbols necessary to implement some of the
   // runtime's functionality.
   if (hasExportSymbolDirective(Args)) {
     if (ForGCOV) {

clang/test/Driver/darwin-ld.c

 // LINK_VERSION_DIGITS-NOT: invalid version number in '-mlinker-version=133.3'
 // LINK_VERSION_DIGITS-NOT: invalid version number in '-mlinker-version=133.3.0'
 // LINK_VERSION_DIGITS-NOT: invalid version number in '-mlinker-version=133.3.0.1'
 // LINK_VERSION_DIGITS-NOT: invalid version number in '-mlinker-version=133.3.0.1.2'
 // LINK_VERSION_DIGITS: invalid version number in '-mlinker-version=133.3.0.1.2.6'
 // LINK_VERSION_DIGITS: invalid version number in '-mlinker-version=133.3.0.1.a'
 // LINK_VERSION_DIGITS: invalid version number in '-mlinker-version=133.3.0.1a'
 
-// RUN: %clang -target x86_64-apple-ios6.0 -miphoneos-version-min=6.0 -fprofile-instr-generate -### %t.o 2> %t.log
-// RUN: FileCheck -check-prefix=LINK_PROFILE_FIRST %s < %t.log
-// RUN: %clang -target x86_64-apple-darwin12 -fprofile-instr-generate -### %t.o 2> %t.log
-// RUN: FileCheck -check-prefix=LINK_PROFILE_FIRST %s < %t.log
-// RUN: %clang -target i386-apple-darwin9 -fprofile-instr-generate -### %t.o 2> %t.log
-// RUN: FileCheck -check-prefix=LINK_PROFILE_FIRST %s < %t.log
-// RUN: %clang -target arm64-apple-ios5.0 -miphoneos-version-min=5.0 -fprofile-instr-generate -### %t.o 2> %t.log
-// RUN: FileCheck -check-prefix=LINK_PROFILE_FIRST %s < %t.log
-// LINK_PROFILE_FIRST: {{ld(.exe)?"}} "{{[^"]+}}libclang_rt.profile_{{[a-z]+}}.a"
-
 // RUN: %clang -target x86_64-apple-darwin12 -fprofile-instr-generate -### %t.o 2> %t.log
 // RUN: FileCheck -check-prefix=PROFILE_SECTALIGN %s < %t.log
 // RUN: %clang -target arm64-apple-ios12 -fprofile-instr-generate -### %t.o 2> %t.log
 // RUN: FileCheck -check-prefix=PROFILE_SECTALIGN %s < %t.log
 // PROFILE_SECTALIGN: "-sectalign" "__DATA" "__llvm_prf_cnts" "0x4000" "-sectalign" "__DATA" "__llvm_prf_data" "0x4000"
 
 // RUN: %clang -target x86_64-apple-darwin12 -fprofile-instr-generate -exported_symbols_list /dev/null -### %t.o 2> %t.log
 // RUN: FileCheck -check-prefix=PROFILE_EXPORT %s < %t.log