[TLS] New lower emutls pass, fix linkage bugs.

Previous implementation in http://reviews.llvm.org/D10522
created external references to __emutls_v.* variables.
Such references are inaccurate and cannot be handled by
all linkers, e.g. Android dynamic and gold linkers for aarch64.

Now a new LowerEmuTLS pass to go through all global variables,
and add emutls_v.* and emutls_t.* variables.
These __emutls* variables have the same linkage and
visibility as the associated user defined TLS variable.

Also removed old code that dump __emutls* variables in AsmPrinter.cpp,
and updated TLS unit tests.

Differential Revision: http://reviews.llvm.org/D15300



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@257718 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 159 insertions, 0 deletions

diff --git a/lib/CodeGen/LowerEmuTLS.cpp b/lib/CodeGen/LowerEmuTLS.cpp
new file mode 100644
index 00000000000..58655dc043d
--- /dev/null
+++ b/lib/CodeGen/LowerEmuTLS.cpp
@@ -0,0 +1,159 @@
+//===- LowerEmuTLS.cpp - Add __emutls_[vt].* variables --------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This transformation is required for targets depending on libgcc style
+// emulated thread local storage variables. For every defined TLS variable xyz,
+// an __emutls_v.xyz is generated. If there is non-zero initialized value
+// an __emutls_t.xyz is also generated.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Target/TargetLowering.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "loweremutls"
+
+namespace {
+
+class LowerEmuTLS : public ModulePass {
+  const TargetMachine *TM;
+public:
+  static char ID; // Pass identification, replacement for typeid
+  explicit LowerEmuTLS() : ModulePass(ID), TM(nullptr) { }
+  explicit LowerEmuTLS(const TargetMachine *TM)
+      : ModulePass(ID), TM(TM) {
+    initializeLowerEmuTLSPass(*PassRegistry::getPassRegistry());
+  }
+  bool runOnModule(Module &M) override;
+private:
+  bool addEmuTlsVar(Module &M, const GlobalVariable *GV);
+  static void copyLinkageVisibility(Module &M,
+                                    const GlobalVariable *from,
+                                    GlobalVariable *to) {
+    to->setLinkage(from->getLinkage());
+    to->setVisibility(from->getVisibility());
+    if (from->hasComdat()) {
+      to->setComdat(M.getOrInsertComdat(to->getName()));
+      to->getComdat()->setSelectionKind(from->getComdat()->getSelectionKind());
+    }
+  }
+};
+}
+
+char LowerEmuTLS::ID = 0;
+
+INITIALIZE_PASS(LowerEmuTLS, "loweremutls",
+                "Add __emutls_[vt]. variables for emultated TLS model",
+                false, false)
+
+ModulePass *llvm::createLowerEmuTLSPass(const TargetMachine *TM) {
+  return new LowerEmuTLS(TM);
+}
+
+bool LowerEmuTLS::runOnModule(Module &M) {
+  if (!TM || !TM->Options.EmulatedTLS)
+    return false;
+
+  bool Changed = false;
+  SmallVector<const GlobalVariable*, 8> TlsVars;
+  for (const auto &G : M.globals()) {
+    if (G.isThreadLocal())
+      TlsVars.append({&G});
+  }
+  for (const auto G : TlsVars)
+    Changed |= addEmuTlsVar(M, G);
+  return Changed;
+}
+
+bool LowerEmuTLS::addEmuTlsVar(Module &M, const GlobalVariable *GV) {
+  LLVMContext &C = M.getContext();
+  PointerType *VoidPtrType = Type::getInt8PtrTy(C);
+
+  std::string EmuTlsVarName = ("__emutls_v." + GV->getName()).str();
+  GlobalVariable *EmuTlsVar = M.getNamedGlobal(EmuTlsVarName);
+  if (EmuTlsVar)
+    return false;  // It has been added before.
+
+  const DataLayout &DL = M.getDataLayout();
+  Constant *NullPtr = ConstantPointerNull::get(VoidPtrType);
+
+  // Get non-zero initializer from GV's initializer.
+  const Constant *InitValue = nullptr;
+  if (GV->hasInitializer()) {
+    InitValue = GV->getInitializer();
+    const ConstantInt *InitIntValue = dyn_cast<ConstantInt>(InitValue);
+    // When GV's init value is all 0, omit the EmuTlsTmplVar and let
+    // the emutls library function to reset newly allocated TLS variables.
+    if (isa<ConstantAggregateZero>(InitValue) ||
+        (InitIntValue && InitIntValue->isZero()))
+      InitValue = nullptr;
+  }
+
+  // Create the __emutls_v. symbol, whose type has 4 fields:
+  //     word size;   // size of GV in bytes
+  //     word align;  // alignment of GV
+  //     void *ptr;   // initialized to 0; set at run time per thread.
+  //     void *templ; // 0 or point to __emutls_t.*
+  // sizeof(word) should be the same as sizeof(void*) on target.
+  IntegerType *WordType = DL.getIntPtrType(C);
+  PointerType *InitPtrType = InitValue ?
+      PointerType::getUnqual(InitValue->getType()) : VoidPtrType;
+  Type *ElementTypes[4] = {WordType, WordType, VoidPtrType, InitPtrType};
+  ArrayRef<Type*> ElementTypeArray(ElementTypes, 4);
+  StructType *EmuTlsVarType = StructType::create(ElementTypeArray);
+  EmuTlsVar = cast<GlobalVariable>(
+      M.getOrInsertGlobal(EmuTlsVarName, EmuTlsVarType));
+  copyLinkageVisibility(M, GV, EmuTlsVar);
+
+  // Define "__emutls_t.*" and "__emutls_v.*" only if GV is defined.
+  if (!GV->hasInitializer())
+    return true;
+
+  Type *GVType = GV->getValueType();
+  unsigned GVAlignment = GV->getAlignment();
+  if (!GVAlignment) {
+    // When LLVM IL declares a variable without alignment, use
+    // the ABI default alignment for the type.
+    GVAlignment = DL.getABITypeAlignment(GVType);
+  }
+
+  // Define "__emutls_t.*" if there is InitValue
+  GlobalVariable *EmuTlsTmplVar = nullptr;
+  if (InitValue) {
+    std::string EmuTlsTmplName = ("__emutls_t." + GV->getName()).str();
+    EmuTlsTmplVar = dyn_cast_or_null<GlobalVariable>(
+        M.getOrInsertGlobal(EmuTlsTmplName, GVType));
+    assert(EmuTlsTmplVar && "Failed to create emualted TLS initializer");
+    EmuTlsTmplVar->setConstant(true);
+    EmuTlsTmplVar->setInitializer(const_cast<Constant*>(InitValue));
+    EmuTlsTmplVar->setAlignment(GVAlignment);
+    copyLinkageVisibility(M, GV, EmuTlsTmplVar);
+  }
+
+  // Define "__emutls_v.*" with initializer and alignment.
+  Constant *ElementValues[4] = {
+      ConstantInt::get(WordType, DL.getTypeStoreSize(GVType)),
+      ConstantInt::get(WordType, GVAlignment),
+      NullPtr, EmuTlsTmplVar ? EmuTlsTmplVar : NullPtr
+  };
+  ArrayRef<Constant*> ElementValueArray(ElementValues, 4);
+  EmuTlsVar->setInitializer(
+      ConstantStruct::get(EmuTlsVarType, ElementValueArray));
+  unsigned MaxAlignment = std::max(
+      DL.getABITypeAlignment(WordType),
+      DL.getABITypeAlignment(VoidPtrType));
+  EmuTlsVar->setAlignment(MaxAlignment);
+  return true;
+}