1 files changed, 146 insertions, 0 deletions
diff --git a/lib/LTO/UpdateCompilerUsed.cpp b/lib/LTO/UpdateCompilerUsed.cpp
new file mode 100644
index 000000000000..a574db6fb5aa
--- /dev/null
+++ b/lib/LTO/UpdateCompilerUsed.cpp
@@ -0,0 +1,146 @@
+//==-LTOInternalize.cpp - LLVM Link Time Optimizer Internalization Utility -==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a helper to run the internalization part of LTO.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LTO/legacy/UpdateCompilerUsed.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/IR/LegacyPassManager.h"
+#include "llvm/IR/Mangler.h"
+#include "llvm/Target/TargetLowering.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
+#include "llvm/Transforms/IPO/Internalize.h"
+
+using namespace llvm;
+
+namespace {
+
+// Helper class that collects AsmUsed and user supplied libcalls.
+class PreserveLibCallsAndAsmUsed {
+public:
+  PreserveLibCallsAndAsmUsed(const StringSet<> &AsmUndefinedRefs,
+                             const TargetMachine &TM,
+                             SmallPtrSetImpl<const GlobalValue *> &LLVMUsed)
+      : AsmUndefinedRefs(AsmUndefinedRefs), TM(TM), LLVMUsed(LLVMUsed) {}
+
+  void findInModule(const Module &TheModule) {
+    initializeLibCalls(TheModule);
+    for (const Function &F : TheModule)
+      findLibCallsAndAsm(F);
+    for (const GlobalVariable &GV : TheModule.globals())
+      findLibCallsAndAsm(GV);
+    for (const GlobalAlias &GA : TheModule.aliases())
+      findLibCallsAndAsm(GA);
+  }
+
+private:
+  // Inputs
+  const StringSet<> &AsmUndefinedRefs;
+  const TargetMachine &TM;
+
+  // Temps
+  llvm::Mangler Mangler;
+  StringSet<> Libcalls;
+
+  // Output
+  SmallPtrSetImpl<const GlobalValue *> &LLVMUsed;
+
+  // Collect names of runtime library functions. User-defined functions with the
+  // same names are added to llvm.compiler.used to prevent them from being
+  // deleted by optimizations.
+  void initializeLibCalls(const Module &TheModule) {
+    TargetLibraryInfoImpl TLII(Triple(TM.getTargetTriple()));
+    TargetLibraryInfo TLI(TLII);
+
+    // TargetLibraryInfo has info on C runtime library calls on the current
+    // target.
+    for (unsigned I = 0, E = static_cast<unsigned>(LibFunc::NumLibFuncs);
+         I != E; ++I) {
+      LibFunc::Func F = static_cast<LibFunc::Func>(I);
+      if (TLI.has(F))
+        Libcalls.insert(TLI.getName(F));
+    }
+
+    SmallPtrSet<const TargetLowering *, 1> TLSet;
+
+    for (const Function &F : TheModule) {
+      const TargetLowering *Lowering =
+          TM.getSubtargetImpl(F)->getTargetLowering();
+
+      if (Lowering && TLSet.insert(Lowering).second)
+        // TargetLowering has info on library calls that CodeGen expects to be
+        // available, both from the C runtime and compiler-rt.
+        for (unsigned I = 0, E = static_cast<unsigned>(RTLIB::UNKNOWN_LIBCALL);
+             I != E; ++I)
+          if (const char *Name =
+                  Lowering->getLibcallName(static_cast<RTLIB::Libcall>(I)))
+            Libcalls.insert(Name);
+    }
+  }
+
+  void findLibCallsAndAsm(const GlobalValue &GV) {
+    // There are no restrictions to apply to declarations.
+    if (GV.isDeclaration())
+      return;
+
+    // There is nothing more restrictive than private linkage.
+    if (GV.hasPrivateLinkage())
+      return;
+
+    // Conservatively append user-supplied runtime library functions to
+    // llvm.compiler.used.  These could be internalized and deleted by
+    // optimizations like -globalopt, causing problems when later optimizations
+    // add new library calls (e.g., llvm.memset => memset and printf => puts).
+    // Leave it to the linker to remove any dead code (e.g. with -dead_strip).
+    if (isa<Function>(GV) && Libcalls.count(GV.getName()))
+      LLVMUsed.insert(&GV);
+
+    SmallString<64> Buffer;
+    TM.getNameWithPrefix(Buffer, &GV, Mangler);
+    if (AsmUndefinedRefs.count(Buffer))
+      LLVMUsed.insert(&GV);
+  }
+};
+
+} // namespace anonymous
+
+void llvm::updateCompilerUsed(Module &TheModule, const TargetMachine &TM,
+                              const StringSet<> &AsmUndefinedRefs) {
+  SmallPtrSet<const GlobalValue *, 8> UsedValues;
+  PreserveLibCallsAndAsmUsed(AsmUndefinedRefs, TM, UsedValues)
+      .findInModule(TheModule);
+
+  if (UsedValues.empty())
+    return;
+
+  llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(TheModule.getContext());
+  std::vector<Constant *> UsedValuesList;
+  for (const auto *GV : UsedValues) {
+    Constant *c =
+        ConstantExpr::getBitCast(const_cast<GlobalValue *>(GV), i8PTy);
+    UsedValuesList.push_back(c);
+  }
+
+  GlobalVariable *LLVMUsed = TheModule.getGlobalVariable("llvm.compiler.used");
+  if (LLVMUsed) {
+    ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
+    for (auto &V : Inits->operands())
+      UsedValuesList.push_back(cast<Constant>(&V));
+    LLVMUsed->eraseFromParent();
+  }
+
+  llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, UsedValuesList.size());
+  LLVMUsed = new llvm::GlobalVariable(
+      TheModule, ATy, false, llvm::GlobalValue::AppendingLinkage,
+      llvm::ConstantArray::get(ATy, UsedValuesList), "llvm.compiler.used");
+
+  LLVMUsed->setSection("llvm.metadata");
+}