Put "built-in" function definitions in global Used list, for LTO. (fix bug 34169)

When building with LTO, builtin functions that are defined but whose calls have not been inserted yet, get internalized. The Global Dead Code Elimination phase in the new LTO implementation then removes these function definitions. Later optimizations add calls to those functions, and the linker then dies complaining that there are no definitions. This CL fixes the new LTO implementation to check if a function is builtin, and if so, to not internalize (and later DCE) the function. As part of this fix I needed to move the RuntimeLibcalls.{def,h} files from the CodeGen subidrectory to the IR subdirectory. I have updated all the files that accessed those two files to access their new location.

Fixes PR34169

Patch by Caroline Tice!

Differential Revision: https://reviews.llvm.org/D49434

llvm-svn: 337847

Author: pcc

llvm/include/llvm/CodeGen/RuntimeLibcalls.h

@@ -29,7 +29,7 @@ namespace RTLIB {
   ///
   enum Libcall {
 #define HANDLE_LIBCALL(code, name) code,
-    #include "RuntimeLibcalls.def"
+    #include "llvm/IR/RuntimeLibcalls.def"
 #undef HANDLE_LIBCALL
   };
 

llvm/include/llvm/CodeGen/RuntimeLibcalls.def llvm/include/llvm/IR/RuntimeLibcalls.def

@@ -26,7 +26,6 @@ module LLVM_Backend {
     // These are intended for (repeated) textual inclusion.
     textual header "CodeGen/CommandFlags.inc"
     textual header "CodeGen/DIEValue.def"
-    textual header "CodeGen/RuntimeLibcalls.def"
   }
 
   module Target {
@@ -222,6 +221,7 @@ module LLVM_IR {
   textual header "IR/Instruction.def"
   textual header "IR/Metadata.def"
   textual header "IR/Value.def"
+  textual header "IR/RuntimeLibcalls.def"
 }
 
 module LLVM_IRReader { requires cplusplus umbrella "IRReader" module * { export * } }

llvm/include/llvm/module.modulemap

@@ -118,7 +118,7 @@ static cl::opt<int> MinPercentageForPredictableBranch(
 void TargetLoweringBase::InitLibcalls(const Triple &TT) {
 #define HANDLE_LIBCALL(code, name) \
   setLibcallName(RTLIB::code, name);
-#include "llvm/CodeGen/RuntimeLibcalls.def"
+#include "llvm/IR/RuntimeLibcalls.def"
 #undef HANDLE_LIBCALL
   // Initialize calling conventions to their default.
   for (int LC = 0; LC < RTLIB::UNKNOWN_LIBCALL; ++LC)

llvm/lib/CodeGen/TargetLoweringBase.cpp

@@ -42,6 +42,12 @@
 using namespace llvm;
 using namespace irsymtab;
 
+static const char *LibcallRoutineNames[] = {
+#define HANDLE_LIBCALL(code, name) name,
+#include "llvm/IR/RuntimeLibcalls.def"
+#undef HANDLE_LIBCALL
+};
+
 namespace {
 
 const char *getExpectedProducerName() {
@@ -226,7 +232,13 @@ Error Builder::addSymbol(const ModuleSymbolTable &Msymtab,
 
   setStr(Sym.IRName, GV->getName());
 
-  if (Used.count(GV))
+  bool IsBuiltinFunc = false;
+
+  for (const char *LibcallName : LibcallRoutineNames)
+    if (GV->getName() == LibcallName)
+      IsBuiltinFunc = true;
+
+  if (Used.count(GV) || IsBuiltinFunc)
     Sym.Flags |= 1 << storage::Symbol::FB_used;
   if (GV->isThreadLocal())
     Sym.Flags |= 1 << storage::Symbol::FB_tls;

llvm/lib/Object/IRSymtab.cpp

@@ -470,7 +470,7 @@ struct StaticLibcallNameMap {
   StaticLibcallNameMap() {
     static const std::pair<const char *, RTLIB::Libcall> NameLibcalls[] = {
 #define HANDLE_LIBCALL(code, name) {(const char *)name, RTLIB::code},
-#include "llvm/CodeGen/RuntimeLibcalls.def"
+#include "llvm/IR/RuntimeLibcalls.def"
 #undef HANDLE_LIBCALL
     };
     for (const auto &NameLibcall : NameLibcalls) {