[XCore] Move lowering of thread local storage to a separate pass.

Thread local storage is not supported by the XMOS linker so we handle
thread local variables by lowering the variable to an array of n elements
(where n is the number of hardware threads per core, currently 8
for all XMOS devices) indexed by the the current thread ID.

Previously this lowering was spread across the XCoreISelLowering and the
XCoreAsmPrinter classes. Moving this to a separate pass should be much
cleaner.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181124 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/XCore/XCoreLowerThreadLocal.cpp

@@ -0,0 +1,145 @@
+//===-- XCoreLowerThreadLocal - Lower thread local variables --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// \brief This file contains a pass that lowers thread local variables on the
+///        XCore.
+///
+//===----------------------------------------------------------------------===//
+
+#include "XCore.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CommandLine.h"
+
+#define DEBUG_TYPE "xcore-lower-thread-local"
+
+using namespace llvm;
+
+static cl::opt<unsigned> MaxThreads(
+  "xcore-max-threads", cl::Optional,
+  cl::desc("Maximum number of threads (for emulation thread-local storage)"),
+  cl::Hidden, cl::value_desc("number"), cl::init(8));
+
+namespace {
+  /// Lowers thread local variables on the XCore. Each thread local variable is
+  /// expanded to an array of n elements indexed by the thread ID where n is the
+  /// fixed number hardware threads supported by the device.
+  struct XCoreLowerThreadLocal : public ModulePass {
+    static char ID;
+
+    XCoreLowerThreadLocal() : ModulePass(ID) {
+      initializeXCoreLowerThreadLocalPass(*PassRegistry::getPassRegistry());
+    }
+
+    bool lowerGlobal(GlobalVariable *GV);
+
+    bool runOnModule(Module &M);
+  };
+}
+
+char XCoreLowerThreadLocal::ID = 0;
+
+INITIALIZE_PASS(XCoreLowerThreadLocal, "xcore-lower-thread-local",
+                "Lower thread local variables", false, false)
+
+ModulePass *llvm::createXCoreLowerThreadLocalPass() {
+  return new XCoreLowerThreadLocal();
+}
+
+static ArrayType *createLoweredType(Type *OriginalType) {
+  return ArrayType::get(OriginalType, MaxThreads);
+}
+
+static Constant *
+createLoweredInitializer(ArrayType *NewType, Constant *OriginalInitializer) {
+  SmallVector<Constant *, 8> Elements(MaxThreads);
+  for (unsigned i = 0; i != MaxThreads; ++i) {
+    Elements[i] = OriginalInitializer;
+  }
+  return ConstantArray::get(NewType, Elements);
+}
+
+static bool hasNonInstructionUse(GlobalVariable *GV) {
+  for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;
+       ++UI)
+    if (!isa<Instruction>(*UI))
+      return true;
+
+  return false;
+}
+
+static bool isZeroLengthArray(Type *Ty) {
+  ArrayType *AT = dyn_cast<ArrayType>(Ty);
+  return AT && (AT->getNumElements() == 0);
+}
+
+bool XCoreLowerThreadLocal::lowerGlobal(GlobalVariable *GV) {
+  Module *M = GV->getParent();
+  LLVMContext &Ctx = M->getContext();
+  if (!GV->isThreadLocal())
+    return false;
+
+  // Skip globals that we can't lower and leave it for the backend to error.
+  if (hasNonInstructionUse(GV) ||
+      !GV->getType()->isSized() || isZeroLengthArray(GV->getType()))
+    return false;
+
+  // Create replacement global.
+  ArrayType *NewType = createLoweredType(GV->getType()->getElementType());
+  Constant *NewInitializer = createLoweredInitializer(NewType,
+                                                      GV->getInitializer());
+  GlobalVariable *NewGV =
+    new GlobalVariable(*M, NewType, GV->isConstant(), GV->getLinkage(),
+                       NewInitializer, "", 0, GlobalVariable::NotThreadLocal,
+                       GV->getType()->getAddressSpace(),
+                       GV->isExternallyInitialized());
+
+  // Update uses.
+  SmallVector<User *, 16> Users(GV->use_begin(), GV->use_end());
+  for (unsigned I = 0, E = Users.size(); I != E; ++I) {
+    User *U = Users[I];
+    Instruction *Inst = cast<Instruction>(U);
+    IRBuilder<> Builder(Inst);
+    Function *GetID = Intrinsic::getDeclaration(GV->getParent(),
+                                                Intrinsic::xcore_getid);
+    Value *ThreadID = Builder.CreateCall(GetID);
+    SmallVector<Value *, 2> Indices;
+    Indices.push_back(Constant::getNullValue(Type::getInt64Ty(Ctx)));
+    Indices.push_back(ThreadID);
+    Value *Addr = Builder.CreateInBoundsGEP(NewGV, Indices);
+    U->replaceUsesOfWith(GV, Addr);
+  }
+
+  // Remove old global.
+  NewGV->takeName(GV);
+  GV->eraseFromParent();
+  return true;
+}
+
+bool XCoreLowerThreadLocal::runOnModule(Module &M) {
+  // Find thread local globals.
+  bool MadeChange = false;
+  SmallVector<GlobalVariable *, 16> ThreadLocalGlobals;
+  for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
+       GVI != E; ++GVI) {
+    GlobalVariable *GV = GVI;
+    if (GV->isThreadLocal())
+      ThreadLocalGlobals.push_back(GV);
+  }
+  for (unsigned I = 0, E = ThreadLocalGlobals.size(); I != E; ++I) {
+    MadeChange |= lowerGlobal(ThreadLocalGlobals[I]);
+  }
+  return MadeChange;
+}