IR: Add entry/exit instrumentation symbols to the libcall list.

[pcc]

Summary

This is necessary in order for these symbols to be handled correctly
during LTO.

[tejohnson]

llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp

23

Can you include RuntimeLibcalls.def and assert that the name is in that list?

[pcc]

llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp

23

I could, but I don't think we need to do that unless there's evidence that people are ignoring the comment.

[tejohnson]

llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp

23

I'd prefer an assert, because I think it would be easy to miss the comment if the second if block is extended with another func name, or a subsequent new if block is added below it.

[pcc]

llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp

23

How about just putting a comment in all the places where people are likely to add new code to this function (before ifs, at the end)?

[pcc]

llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp

23

I suppose another idea is to do something like

#define HANDLE_LIBCALL(name, value) const char LibCallName_##name[] = value;
#include "llvm/IR/RuntimeLibcalls.def"

in a header somewhere, and then change this code to use LibCallName_FOO.

[tejohnson]

Needs a test.

llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp

23

Sure that would work too (I was originally envisioning something like what is done in IRSymtab.cpp except assert that IsBuiltinFunc, but your idea is more efficient). Why would it need to be in a header rather than in this file?

Better to enforce consistency at compile time if possible IMO.

[dexonsmith]

[Marking as "Request Changes" to get this out of my queue.]

llvm/include/llvm/IR/RuntimeLibcalls.def

 HANDLE_LIBCALL(ATOMIC_FETCH_NAND_16, "__atomic_fetch_nand_16")
 
 // Stack Protector Fail
 HANDLE_LIBCALL(STACKPROTECTOR_CHECK_FAIL, "__stack_chk_fail")
 
 // Deoptimization
 HANDLE_LIBCALL(DEOPTIMIZE, "__llvm_deoptimize")
 
+// Entry/exit instrumentation (lib/Transforms/Utils/EntryExitInstrumenter.cpp).
+HANDLE_LIBCALL(ENTRYEXIT1, "mcount")
+HANDLE_LIBCALL(ENTRYEXIT2, ".mcount")
+HANDLE_LIBCALL(ENTRYEXIT3, "\01__gnu_mcount_nc")
+HANDLE_LIBCALL(ENTRYEXIT4, "\01_mcount")
+HANDLE_LIBCALL(ENTRYEXIT5, "\01mcount")
+HANDLE_LIBCALL(ENTRYEXIT6, "__mcount")
+HANDLE_LIBCALL(ENTRYEXIT7, "_mcount")
+HANDLE_LIBCALL(ENTRYEXIT8, "__cyg_profile_func_enter_bare")
+HANDLE_LIBCALL(ENTRYEXIT9, "__cyg_profile_func_enter")
+HANDLE_LIBCALL(ENTRYEXIT10, "__cyg_profile_func_exit")
+
 HANDLE_LIBCALL(UNKNOWN_LIBCALL, nullptr)
 
 #undef HANDLE_LIBCALL

llvm/lib/Transforms/Utils/EntryExitInstrumenter.cpp

 #include "llvm/IR/Module.h"
 #include "llvm/IR/Type.h"
 #include "llvm/Pass.h"
 #include "llvm/Transforms/Utils.h"
 using namespace llvm;
 
 static void insertCall(Function &CurFn, StringRef Func,
                        Instruction *InsertionPt, DebugLoc DL) {
+  // If you add code to recognize a new instrumentation function here, the
+  // function also needs to be added to include/llvm/IR/RuntimeLibcalls.def
+  // so that it is handled correctly by LTO.
   Module &M = *InsertionPt->getParent()->getParent()->getParent();
   LLVMContext &C = InsertionPt->getParent()->getContext();
 
   if (Func == "mcount" ||
       Func == ".mcount" ||
       Func == "\01__gnu_mcount_nc" ||
       Func == "\01_mcount" ||
       Func == "\01mcount" ||