Revert "[ARM] Promote small global constants to constant pools"

This reverts r281604, which adds text relocations to ARM binaries.

llvm-svn: 281645

4 files changed, 1 insertions, 155 deletions

diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
index 8d44a26b1db..186c6431481 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.cpp
@@ -97,13 +97,6 @@ void ARMAsmPrinter::EmitXXStructor(const DataLayout &DL, const Constant *CV) {
   OutStreamer->EmitValue(E, Size);
 }
 
-void ARMAsmPrinter::EmitGlobalVariable(const GlobalVariable *GV) {
-  if (PromotedGlobals.count(GV))
-    // The global was promoted into a constant pool. It should not be emitted.
-    return;
-  AsmPrinter::EmitGlobalVariable(GV);
-}
-
 /// runOnMachineFunction - This uses the EmitInstruction()
 /// method to print assembly for each instruction.
 ///
@@ -116,12 +109,6 @@ bool ARMAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
   const Function* F = MF.getFunction();
   const TargetMachine& TM = MF.getTarget();
 
-  // Collect all globals that had their storage promoted to a constant pool.
-  // Functions are emitted before variables, so this accumulates promoted
-  // globals from all functions in PromotedGlobals.
-  for (auto *GV : AFI->getGlobalsPromotedToConstantPool())
-    PromotedGlobals.insert(GV);
-  
   // Calculate this function's optimization goal.
   unsigned OptimizationGoal;
   if (F->hasFnAttribute(Attribute::OptimizeNone))
diff --git a/llvm/lib/Target/ARM/ARMAsmPrinter.h b/llvm/lib/Target/ARM/ARMAsmPrinter.h
index 30abdbc322a..97f5ca0ecbc 100644
--- a/llvm/lib/Target/ARM/ARMAsmPrinter.h
+++ b/llvm/lib/Target/ARM/ARMAsmPrinter.h
@@ -56,12 +56,6 @@ class LLVM_LIBRARY_VISIBILITY ARMAsmPrinter : public AsmPrinter {
   /// -1 if uninitialized, 0 if conflicting goals
   int OptimizationGoals;
 
-  /// List of globals that have had their storage promoted to a constant
-  /// pool. This lives between calls to runOnMachineFunction and collects
-  /// data from every MachineFunction. It is used during doFinalization
-  /// when all non-function globals are emitted.
-  SmallPtrSet<const GlobalVariable*,2> PromotedGlobals;
-
 public:
   explicit ARMAsmPrinter(TargetMachine &TM,
                          std::unique_ptr<MCStreamer> Streamer);
@@ -96,8 +90,7 @@ public:
   void EmitStartOfAsmFile(Module &M) override;
   void EmitEndOfAsmFile(Module &M) override;
   void EmitXXStructor(const DataLayout &DL, const Constant *CV) override;
-  void EmitGlobalVariable(const GlobalVariable *GV) override;
-  
+
   // lowerOperand - Convert a MachineOperand into the equivalent MCOperand.
   bool lowerOperand(const MachineOperand &MO, MCOperand &MCOp);
 
diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 0d75d5eb7ae..434b4546483 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -59,24 +59,12 @@ using namespace llvm;
 STATISTIC(NumTailCalls, "Number of tail calls");
 STATISTIC(NumMovwMovt, "Number of GAs materialized with movw + movt");
 STATISTIC(NumLoopByVals, "Number of loops generated for byval arguments");
-STATISTIC(NumConstpoolPromoted,
-  "Number of constants with their storage promoted into constant pools");
 
 static cl::opt<bool>
 ARMInterworking("arm-interworking", cl::Hidden,
   cl::desc("Enable / disable ARM interworking (for debugging only)"),
   cl::init(true));
 
-static cl::opt<bool> EnableConstpoolPromotion(
-    "arm-promote-constant", cl::Hidden,
-    cl::desc("Enable / disable promotion of unnamed_addr constants into "
-             "constant pools"),
-    cl::init(true));
-static cl::opt<unsigned> ConstpoolPromotionMaxSize(
-    "arm-promote-constant-max-size", cl::Hidden,
-    cl::desc("Maximum size of constant to promote into a constant pool"),
-    cl::init(64));
-
 namespace {
   class ARMCCState : public CCState {
   public:
@@ -2975,110 +2963,6 @@ ARMTargetLowering::LowerGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const {
   llvm_unreachable("bogus TLS model");
 }
 
-/// Return true if all users of V are within function F, looking through
-/// ConstantExprs.
-static bool allUsersAreInFunction(const Value *V, const Function *F) {
-  SmallVector<const User*,4> Worklist;
-  for (auto *U : V->users())
-    Worklist.push_back(U);
-  while (!Worklist.empty()) {
-    auto *U = Worklist.pop_back_val();
-    if (isa<ConstantExpr>(U)) {
-      for (auto *UU : U->users())
-        Worklist.push_back(UU);
-      continue;
-    }
-
-    auto *I = dyn_cast<Instruction>(U);
-    if (!I || I->getParent()->getParent() != F)
-      return false;
-  }
-  return true;
-}
-
-/// Return true if all users of V are within some (any) function, looking through
-/// ConstantExprs. In other words, are there any global constant users?
-static bool allUsersAreInFunctions(const Value *V) {
-  SmallVector<const User*,4> Worklist;
-  for (auto *U : V->users())
-    Worklist.push_back(U);
-  while (!Worklist.empty()) {
-    auto *U = Worklist.pop_back_val();
-    if (isa<ConstantExpr>(U)) {
-      for (auto *UU : U->users())
-        Worklist.push_back(UU);
-      continue;
-    }
-
-    if (!isa<Instruction>(U))
-      return false;
-  }
-  return true;
-}
-
-static SDValue promoteToConstantPool(const GlobalValue *GV, SelectionDAG &DAG,
-                                     EVT PtrVT, SDLoc dl) {
-  // If we're creating a pool entry for a constant global with unnamed address,
-  // and the global is small enough, we can emit it inline into the constant pool
-  // to save ourselves an indirection.
-  //
-  // This is a win if the constant is only used in one function (so it doesn't
-  // need to be duplicated) or duplicating the constant wouldn't increase code
-  // size (implying the constant is no larger than 4 bytes).
-  const Function *F = DAG.getMachineFunction().getFunction();
-
-  // We rely on this decision to inline being idemopotent and unrelated to the
-  // use-site. We know that if we inline a variable at one use site, we'll
-  // inline it elsewhere too (and reuse the constant pool entry). Fast-isel
-  // doesn't know about this optimization, so bail out if it's enabled else
-  // we could decide to inline here (and thus never emit the GV) but require
-  // the GV from fast-isel generated code.
-  if (DAG.getMachineFunction().getTarget().Options.EnableFastISel)
-      return SDValue();
-  
-  auto *GVar = dyn_cast<GlobalVariable>(GV);
-  if (EnableConstpoolPromotion && GVar && GVar->hasInitializer() &&
-      GVar->isConstant() && GVar->hasGlobalUnnamedAddr() &&
-      GVar->hasLocalLinkage()) {
-    // The constant islands pass can only really deal with alignment requests
-    // <= 4 bytes and cannot pad constants itself. Therefore we cannot promote
-    // any type wanting greater alignment requirements than 4 bytes. We also
-    // can only promote constants that are multiples of 4 bytes in size or
-    // are paddable to a multiple of 4. Currently we only try and pad constants
-    // that are strings for simplicity.
-    auto *Init = GVar->getInitializer();
-    auto *CDAInit = dyn_cast<ConstantDataArray>(Init);
-    unsigned Size = DAG.getDataLayout().getTypeAllocSize(Init->getType());
-    unsigned Align = DAG.getDataLayout().getABITypeAlignment(Init->getType());
-    unsigned RequiredPadding = 4 - (Size % 4);
-    bool PaddingPossible =
-        RequiredPadding == 4 || (CDAInit && CDAInit->isString());
-    
-    if (PaddingPossible && Align <= 4 && Size <= ConstpoolPromotionMaxSize &&
-        (allUsersAreInFunction(GVar, F) ||
-         (Size <= 4 && allUsersAreInFunctions(GVar)))) {
-      if (RequiredPadding != 4) {
-        StringRef S = CDAInit->getAsString();
-
-        SmallVector<uint8_t,16> V(S.size());
-        std::copy(S.bytes_begin(), S.bytes_end(), V.begin());
-        while (RequiredPadding--)
-          V.push_back(0);
-        Init = ConstantDataArray::get(*DAG.getContext(), V);
-      }
-      
-      SDValue CPAddr =
-        DAG.getTargetConstantPool(Init, PtrVT, /*Align=*/4);
-      MachineFunction &MF = DAG.getMachineFunction();
-      ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
-      AFI->markGlobalAsPromotedToConstantPool(GVar);
-      ++NumConstpoolPromoted;
-      return DAG.getNode(ARMISD::Wrapper, dl, MVT::i32, CPAddr);
-    }
-  }
-  return SDValue();
-}
-
 SDValue ARMTargetLowering::LowerGlobalAddressELF(SDValue Op,
                                                  SelectionDAG &DAG) const {
   EVT PtrVT = getPointerTy(DAG.getDataLayout());
@@ -3090,11 +2974,6 @@ SDValue ARMTargetLowering::LowerGlobalAddressELF(SDValue Op,
   bool IsRO =
       (isa<GlobalVariable>(GV) && cast<GlobalVariable>(GV)->isConstant()) ||
       isa<Function>(GV);
-  
-  if (TM.shouldAssumeDSOLocal(*GV->getParent(), GV))
-    if (SDValue V = promoteToConstantPool(GV, DAG, PtrVT, dl))
-      return V;
-
   if (isPositionIndependent()) {
     bool UseGOT_PREL = !TM.shouldAssumeDSOLocal(*GV->getParent(), GV);
 
diff --git a/llvm/lib/Target/ARM/ARMMachineFunctionInfo.h b/llvm/lib/Target/ARM/ARMMachineFunctionInfo.h
index 52ba6a49fd5..f71497240ff 100644
--- a/llvm/lib/Target/ARM/ARMMachineFunctionInfo.h
+++ b/llvm/lib/Target/ARM/ARMMachineFunctionInfo.h
@@ -121,9 +121,6 @@ class ARMFunctionInfo : public MachineFunctionInfo {
   /// copies.
   bool IsSplitCSR;
 
-  /// Globals that have had their storage promoted into the constant pool.
-  SmallVector<const GlobalVariable*,2> PromotedGlobals;
-  
 public:
   ARMFunctionInfo() :
     isThumb(false),
@@ -229,16 +226,6 @@ public:
     }
     return It;
   }
-
-  /// Indicate to the backend that \c GV has had its storage changed to inside
-  /// a constant pool. This means it no longer needs to be emitted as a
-  /// global variable.
-  void markGlobalAsPromotedToConstantPool(const GlobalVariable *GV) {
-    PromotedGlobals.push_back(GV);
-  }
-  ArrayRef<const GlobalVariable*> getGlobalsPromotedToConstantPool() {
-    return PromotedGlobals;
-  }
 };
 } // End llvm namespace