Update LLVM for rebase to r212749.
Includes a cherry-pick of:
r212948 - fixes a small issue with atomic calls
Change-Id: Ib97bd980b59f18142a69506400911a6009d9df18
diff --git a/lib/CodeGen/GlobalMerge.cpp b/lib/CodeGen/GlobalMerge.cpp
new file mode 100644
index 0000000..027ee38
--- /dev/null
+++ b/lib/CodeGen/GlobalMerge.cpp
@@ -0,0 +1,361 @@
+//===-- GlobalMerge.cpp - Internal globals merging -----------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// This pass merges globals with internal linkage into one. This way all the
+// globals which were merged into a biggest one can be addressed using offsets
+// from the same base pointer (no need for separate base pointer for each of the
+// global). Such a transformation can significantly reduce the register pressure
+// when many globals are involved.
+//
+// For example, consider the code which touches several global variables at
+// once:
+//
+// static int foo[N], bar[N], baz[N];
+//
+// for (i = 0; i < N; ++i) {
+// foo[i] = bar[i] * baz[i];
+// }
+//
+// On ARM the addresses of 3 arrays should be kept in the registers, thus
+// this code has quite large register pressure (loop body):
+//
+// ldr r1, [r5], #4
+// ldr r2, [r6], #4
+// mul r1, r2, r1
+// str r1, [r0], #4
+//
+// Pass converts the code to something like:
+//
+// static struct {
+// int foo[N];
+// int bar[N];
+// int baz[N];
+// } merged;
+//
+// for (i = 0; i < N; ++i) {
+// merged.foo[i] = merged.bar[i] * merged.baz[i];
+// }
+//
+// and in ARM code this becomes:
+//
+// ldr r0, [r5, #40]
+// ldr r1, [r5, #80]
+// mul r0, r1, r0
+// str r0, [r5], #4
+//
+// note that we saved 2 registers here almostly "for free".
+// ===---------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/IR/Attributes.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Target/TargetLowering.h"
+#include "llvm/Target/TargetLoweringObjectFile.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "global-merge"
+
+cl::opt<bool>
+EnableGlobalMerge("enable-global-merge", cl::Hidden,
+ cl::desc("Enable global merge pass"),
+ cl::init(true));
+
+static cl::opt<bool>
+EnableGlobalMergeOnConst("global-merge-on-const", cl::Hidden,
+ cl::desc("Enable global merge pass on constants"),
+ cl::init(false));
+
+// FIXME: this could be a transitional option, and we probably need to remove
+// it if only we are sure this optimization could always benefit all targets.
+static cl::opt<bool>
+EnableGlobalMergeOnExternal("global-merge-on-external", cl::Hidden,
+ cl::desc("Enable global merge pass on external linkage"),
+ cl::init(false));
+
+STATISTIC(NumMerged , "Number of globals merged");
+namespace {
+ class GlobalMerge : public FunctionPass {
+ const TargetMachine *TM;
+
+ bool doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
+ Module &M, bool isConst, unsigned AddrSpace) const;
+
+ /// \brief Check if the given variable has been identified as must keep
+ /// \pre setMustKeepGlobalVariables must have been called on the Module that
+ /// contains GV
+ bool isMustKeepGlobalVariable(const GlobalVariable *GV) const {
+ return MustKeepGlobalVariables.count(GV);
+ }
+
+ /// Collect every variables marked as "used" or used in a landing pad
+ /// instruction for this Module.
+ void setMustKeepGlobalVariables(Module &M);
+
+ /// Collect every variables marked as "used"
+ void collectUsedGlobalVariables(Module &M);
+
+ /// Keep track of the GlobalVariable that must not be merged away
+ SmallPtrSet<const GlobalVariable *, 16> MustKeepGlobalVariables;
+
+ public:
+ static char ID; // Pass identification, replacement for typeid.
+ explicit GlobalMerge(const TargetMachine *TM = nullptr)
+ : FunctionPass(ID), TM(TM) {
+ initializeGlobalMergePass(*PassRegistry::getPassRegistry());
+ }
+
+ bool doInitialization(Module &M) override;
+ bool runOnFunction(Function &F) override;
+ bool doFinalization(Module &M) override;
+
+ const char *getPassName() const override {
+ return "Merge internal globals";
+ }
+
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
+ AU.setPreservesCFG();
+ FunctionPass::getAnalysisUsage(AU);
+ }
+ };
+} // end anonymous namespace
+
+char GlobalMerge::ID = 0;
+INITIALIZE_TM_PASS(GlobalMerge, "global-merge", "Merge global variables",
+ false, false)
+
+bool GlobalMerge::doMerge(SmallVectorImpl<GlobalVariable*> &Globals,
+ Module &M, bool isConst, unsigned AddrSpace) const {
+ const TargetLowering *TLI = TM->getTargetLowering();
+ const DataLayout *DL = TLI->getDataLayout();
+
+ // FIXME: Infer the maximum possible offset depending on the actual users
+ // (these max offsets are different for the users inside Thumb or ARM
+ // functions)
+ unsigned MaxOffset = TLI->getMaximalGlobalOffset();
+
+ // FIXME: Find better heuristics
+ std::stable_sort(Globals.begin(), Globals.end(),
+ [DL](const GlobalVariable *GV1, const GlobalVariable *GV2) {
+ Type *Ty1 = cast<PointerType>(GV1->getType())->getElementType();
+ Type *Ty2 = cast<PointerType>(GV2->getType())->getElementType();
+
+ return (DL->getTypeAllocSize(Ty1) < DL->getTypeAllocSize(Ty2));
+ });
+
+ Type *Int32Ty = Type::getInt32Ty(M.getContext());
+
+ assert(Globals.size() > 1);
+
+ // FIXME: This simple solution merges globals all together as maximum as
+ // possible. However, with this solution it would be hard to remove dead
+ // global symbols at link-time. An alternative solution could be checking
+ // global symbols references function by function, and make the symbols
+ // being referred in the same function merged and we would probably need
+ // to introduce heuristic algorithm to solve the merge conflict from
+ // different functions.
+ for (size_t i = 0, e = Globals.size(); i != e; ) {
+ size_t j = 0;
+ uint64_t MergedSize = 0;
+ std::vector<Type*> Tys;
+ std::vector<Constant*> Inits;
+
+ bool HasExternal = false;
+ GlobalVariable *TheFirstExternal = 0;
+ for (j = i; j != e; ++j) {
+ Type *Ty = Globals[j]->getType()->getElementType();
+ MergedSize += DL->getTypeAllocSize(Ty);
+ if (MergedSize > MaxOffset) {
+ break;
+ }
+ Tys.push_back(Ty);
+ Inits.push_back(Globals[j]->getInitializer());
+
+ if (Globals[j]->hasExternalLinkage() && !HasExternal) {
+ HasExternal = true;
+ TheFirstExternal = Globals[j];
+ }
+ }
+
+ // If merged variables doesn't have external linkage, we needn't to expose
+ // the symbol after merging.
+ GlobalValue::LinkageTypes Linkage = HasExternal
+ ? GlobalValue::ExternalLinkage
+ : GlobalValue::InternalLinkage;
+
+ StructType *MergedTy = StructType::get(M.getContext(), Tys);
+ Constant *MergedInit = ConstantStruct::get(MergedTy, Inits);
+
+ // If merged variables have external linkage, we use symbol name of the
+ // first variable merged as the suffix of global symbol name. This would
+ // be able to avoid the link-time naming conflict for globalm symbols.
+ GlobalVariable *MergedGV = new GlobalVariable(
+ M, MergedTy, isConst, Linkage, MergedInit,
+ HasExternal ? "_MergedGlobals_" + TheFirstExternal->getName()
+ : "_MergedGlobals",
+ nullptr, GlobalVariable::NotThreadLocal, AddrSpace);
+
+ for (size_t k = i; k < j; ++k) {
+ GlobalValue::LinkageTypes Linkage = Globals[k]->getLinkage();
+ std::string Name = Globals[k]->getName();
+
+ Constant *Idx[2] = {
+ ConstantInt::get(Int32Ty, 0),
+ ConstantInt::get(Int32Ty, k-i)
+ };
+ Constant *GEP = ConstantExpr::getInBoundsGetElementPtr(MergedGV, Idx);
+ Globals[k]->replaceAllUsesWith(GEP);
+ Globals[k]->eraseFromParent();
+
+ if (Linkage != GlobalValue::InternalLinkage) {
+ // Generate a new alias...
+ auto *PTy = cast<PointerType>(GEP->getType());
+ GlobalAlias::create(PTy->getElementType(), PTy->getAddressSpace(),
+ Linkage, Name, GEP, &M);
+ }
+
+ NumMerged++;
+ }
+ i = j;
+ }
+
+ return true;
+}
+
+void GlobalMerge::collectUsedGlobalVariables(Module &M) {
+ // Extract global variables from llvm.used array
+ const GlobalVariable *GV = M.getGlobalVariable("llvm.used");
+ if (!GV || !GV->hasInitializer()) return;
+
+ // Should be an array of 'i8*'.
+ const ConstantArray *InitList = cast<ConstantArray>(GV->getInitializer());
+
+ for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
+ if (const GlobalVariable *G =
+ dyn_cast<GlobalVariable>(InitList->getOperand(i)->stripPointerCasts()))
+ MustKeepGlobalVariables.insert(G);
+}
+
+void GlobalMerge::setMustKeepGlobalVariables(Module &M) {
+ collectUsedGlobalVariables(M);
+
+ for (Module::iterator IFn = M.begin(), IEndFn = M.end(); IFn != IEndFn;
+ ++IFn) {
+ for (Function::iterator IBB = IFn->begin(), IEndBB = IFn->end();
+ IBB != IEndBB; ++IBB) {
+ // Follow the invoke link to find the landing pad instruction
+ const InvokeInst *II = dyn_cast<InvokeInst>(IBB->getTerminator());
+ if (!II) continue;
+
+ const LandingPadInst *LPInst = II->getUnwindDest()->getLandingPadInst();
+ // Look for globals in the clauses of the landing pad instruction
+ for (unsigned Idx = 0, NumClauses = LPInst->getNumClauses();
+ Idx != NumClauses; ++Idx)
+ if (const GlobalVariable *GV =
+ dyn_cast<GlobalVariable>(LPInst->getClause(Idx)
+ ->stripPointerCasts()))
+ MustKeepGlobalVariables.insert(GV);
+ }
+ }
+}
+
+bool GlobalMerge::doInitialization(Module &M) {
+ if (!EnableGlobalMerge)
+ return false;
+
+ DenseMap<unsigned, SmallVector<GlobalVariable*, 16> > Globals, ConstGlobals,
+ BSSGlobals;
+ const TargetLowering *TLI = TM->getTargetLowering();
+ const DataLayout *DL = TLI->getDataLayout();
+ unsigned MaxOffset = TLI->getMaximalGlobalOffset();
+ bool Changed = false;
+ setMustKeepGlobalVariables(M);
+
+ // Grab all non-const globals.
+ for (Module::global_iterator I = M.global_begin(),
+ E = M.global_end(); I != E; ++I) {
+ // Merge is safe for "normal" internal or external globals only
+ if (I->isDeclaration() || I->isThreadLocal() || I->hasSection())
+ continue;
+
+ if (!(EnableGlobalMergeOnExternal && I->hasExternalLinkage()) &&
+ !I->hasInternalLinkage())
+ continue;
+
+ PointerType *PT = dyn_cast<PointerType>(I->getType());
+ assert(PT && "Global variable is not a pointer!");
+
+ unsigned AddressSpace = PT->getAddressSpace();
+
+ // Ignore fancy-aligned globals for now.
+ unsigned Alignment = DL->getPreferredAlignment(I);
+ Type *Ty = I->getType()->getElementType();
+ if (Alignment > DL->getABITypeAlignment(Ty))
+ continue;
+
+ // Ignore all 'special' globals.
+ if (I->getName().startswith("llvm.") ||
+ I->getName().startswith(".llvm."))
+ continue;
+
+ // Ignore all "required" globals:
+ if (isMustKeepGlobalVariable(I))
+ continue;
+
+ if (DL->getTypeAllocSize(Ty) < MaxOffset) {
+ if (TargetLoweringObjectFile::getKindForGlobal(I, *TM).isBSSLocal())
+ BSSGlobals[AddressSpace].push_back(I);
+ else if (I->isConstant())
+ ConstGlobals[AddressSpace].push_back(I);
+ else
+ Globals[AddressSpace].push_back(I);
+ }
+ }
+
+ for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator
+ I = Globals.begin(), E = Globals.end(); I != E; ++I)
+ if (I->second.size() > 1)
+ Changed |= doMerge(I->second, M, false, I->first);
+
+ for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator
+ I = BSSGlobals.begin(), E = BSSGlobals.end(); I != E; ++I)
+ if (I->second.size() > 1)
+ Changed |= doMerge(I->second, M, false, I->first);
+
+ if (EnableGlobalMergeOnConst)
+ for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator
+ I = ConstGlobals.begin(), E = ConstGlobals.end(); I != E; ++I)
+ if (I->second.size() > 1)
+ Changed |= doMerge(I->second, M, true, I->first);
+
+ return Changed;
+}
+
+bool GlobalMerge::runOnFunction(Function &F) {
+ return false;
+}
+
+bool GlobalMerge::doFinalization(Module &M) {
+ MustKeepGlobalVariables.clear();
+ return false;
+}
+
+Pass *llvm::createGlobalMergePass(const TargetMachine *TM) {
+ return new GlobalMerge(TM);
+}