[AIX] Fix Link Issue when `-fprofile-update=[atomic|prefer-atomic]` is in Effect

[qiongsiwu1]

Summary

https://reviews.llvm.org/D157280 enabled -fprofile-update for -fprofile-generate, but omitted adding -latomic to the linker command on AIX. This omission causes linking to fail due to an undefined symbol. This patch fixes the link error.

[qiongsiwu1]

clang/lib/Driver/ToolChains/AIX.cpp

440

This check here is copied from https://github.com/llvm/llvm-project/blob/77596e6b167bf0a5efa790597d6b75ac5e685b55/clang/lib/Driver/ToolChains/Clang.cpp#L867, and I don't think it is good to copy this particular code over because we are doing the same check twice at different places and the code can go out of sync.

May I get some suggestions to avoid duplicating the code? Thanks!

[MaskRay]

clang/lib/Driver/ToolChains/AIX.cpp

440

This seems ok to me. You can also use != "single" instead.

getLastArgNoClaim is probably slightly better.

clang/test/Driver/fprofile-update.c

17

The idiom is to use --target=.... This driver decision is not dependent on what OS the host runs, so %if system-aix should be avoided.

[qiongsiwu1]

Address code review feedback.

[qiongsiwu1]

clang/test/Driver/fprofile-update.c

17

Ah yes thanks for the feedback. Fixed!

[w2yehia]

clang/test/Driver/fprofile-update.c

18

not sure if it's typical to also add a negative test that -latomic is not added by default or with "single" suboption. I'll leave it to you to decide.

[qiongsiwu1]

Address code review. Thanks for the input @w2yehia !

clang/lib/Driver/ToolChains/AIX.cpp

void AIX::addClangTargetOptions(
 
   if (Args.hasFlag(options::OPT_fxl_pragma_pack,
                    options::OPT_fno_xl_pragma_pack, true))
     CC1Args.push_back("-fxl-pragma-pack");
 }
 
 void AIX::addProfileRTLibs(const llvm::opt::ArgList &Args,
                            llvm::opt::ArgStringList &CmdArgs) const {
+  if (needsProfileRT(Args)) {
     // Add linker option -u__llvm_profile_runtime to cause runtime
     // initialization to occur.
-  if (needsProfileRT(Args))
     CmdArgs.push_back(Args.MakeArgString(
         Twine("-u", llvm::getInstrProfRuntimeHookVarName())));
+
+    if (const auto *A =
+            Args.getLastArgNoClaim(options::OPT_fprofile_update_EQ)) {
+      StringRef Val = A->getValue();
+      if (Val == "atomic" || Val == "prefer-atomic")
+        CmdArgs.push_back("-latomic");
+    }
+  }
+
   ToolChain::addProfileRTLibs(Args, CmdArgs);
 }
 
 ToolChain::CXXStdlibType AIX::GetDefaultCXXStdlibType() const {
   return ToolChain::CST_Libcxx;
 }
 
 ToolChain::RuntimeLibType AIX::GetDefaultRuntimeLibType() const {
   return ToolChain::RLT_CompilerRT;
 }
 
 auto AIX::buildAssembler() const -> Tool * { return new aix::Assembler(*this); }
 
 auto AIX::buildLinker() const -> Tool * { return new aix::Linker(*this); }

clang/test/Driver/fprofile-update.c

 /// For -fprofile-instr-generate and -fprofile-arcs, increment counters atomically
 /// if -fprofile-update={atomic,prefer-atomic} is specified.
 // RUN: %clang -### %s -c -fprofile-update=atomic 2>&1 | FileCheck %s
 // RUN: %clang -### %s -c -fprofile-update=prefer-atomic 2>&1 | FileCheck %s
 
 // CHECK: "-fprofile-update=atomic"
 
 // RUN: %clang -### %s -c -fprofile-update=atomic -fprofile-update=single 2>&1 | FileCheck %s --check-prefix=SINGLE
 
 // SINGLE-NOT: "-fprofile-update=atomic"
 
 // RUN: not %clang %s -c -fprofile-update=unknown 2>&1 | FileCheck %s --check-prefix=ERROR
 
 // ERROR: error: unsupported argument 'unknown' to option '-fprofile-update='
+
+// AIX specific tests
+// RUN: %clang -### %s --target=powerpc-unknown-aix -fprofile-generate -fprofile-update=atomic 2>&1 | FileCheck %s --check-prefix=AIX
+// RUN: %clang -### %s --target=powerpc-unknown-aix -fprofile-generate -fprofile-update=prefer-atomic 2>&1 | FileCheck %s --check-prefix=AIX
+// RUN: %clang -### %s --target=powerpc-unknown-aix -fprofile-generate 2>&1 | FileCheck %s --check-prefix=AIX-NOATOMIC
+// RUN: %clang -### %s --target=powerpc-unknown-aix -fprofile-generate -fprofile-update=single 2>&1 | FileCheck %s --check-prefix=AIX-NOATOMIC
+// AIX: "-latomic"
+// AIX-NOATOMIC-NOT: "-latomic"