[NVPTX] Handle addrspacecast constant expressions in aggregate initializers

We need to track if an AddrSpaceCast expression was seen when
generating an MCExpr for a ConstantExpr.  This change introduces a
custom lowerConstant method to the NVPTX asm printer that will create
NVPTXGenericMCSymbolRefExpr nodes at the appropriate places to encode
the information that a given symbol needs to be casted to a generic
address.

llvm-svn: 236000

Author: jholewinski-nv

llvm/lib/Target/NVPTX/NVPTXAsmPrinter.cpp

@@ -1983,6 +1983,212 @@ bool NVPTXAsmPrinter::ignoreLoc(const MachineInstr &MI) {
   return false;
 }
 
+/// lowerConstantForGV - Return an MCExpr for the given Constant.  This is mostly
+/// a copy from AsmPrinter::lowerConstant, except customized to only handle
+/// expressions that are representable in PTX and create
+/// NVPTXGenericMCSymbolRefExpr nodes for addrspacecast instructions.
+const MCExpr *
+NVPTXAsmPrinter::lowerConstantForGV(const Constant *CV, bool ProcessingGeneric) {
+  MCContext &Ctx = OutContext;
+
+  if (CV->isNullValue() || isa<UndefValue>(CV))
+    return MCConstantExpr::Create(0, Ctx);
+
+  if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV))
+    return MCConstantExpr::Create(CI->getZExtValue(), Ctx);
+
+  if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV)) {
+    const MCSymbolRefExpr *Expr =
+      MCSymbolRefExpr::Create(getSymbol(GV), Ctx);
+    if (ProcessingGeneric) {
+      return NVPTXGenericMCSymbolRefExpr::Create(Expr, Ctx);
+    } else {
+      return Expr;
+    }
+  }
+
+  const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
+  if (!CE) {
+    llvm_unreachable("Unknown constant value to lower!");
+  }
+
+  switch (CE->getOpcode()) {
+  default:
+    // If the code isn't optimized, there may be outstanding folding
+    // opportunities. Attempt to fold the expression using DataLayout as a
+    // last resort before giving up.
+    if (Constant *C = ConstantFoldConstantExpression(CE, *TM.getDataLayout()))
+      if (C != CE)
+        return lowerConstantForGV(C, ProcessingGeneric);
+
+    // Otherwise report the problem to the user.
+    {
+      std::string S;
+      raw_string_ostream OS(S);
+      OS << "Unsupported expression in static initializer: ";
+      CE->printAsOperand(OS, /*PrintType=*/false,
+                     !MF ? nullptr : MF->getFunction()->getParent());
+      report_fatal_error(OS.str());
+    }
+
+  case Instruction::AddrSpaceCast: {
+    // Strip the addrspacecast and pass along the operand
+    PointerType *DstTy = cast<PointerType>(CE->getType());
+    if (DstTy->getAddressSpace() == 0) {
+      return lowerConstantForGV(cast<const Constant>(CE->getOperand(0)), true);
+    }
+    std::string S;
+    raw_string_ostream OS(S);
+    OS << "Unsupported expression in static initializer: ";
+    CE->printAsOperand(OS, /*PrintType=*/ false,
+                       !MF ? 0 : MF->getFunction()->getParent());
+    report_fatal_error(OS.str());
+  }
+
+  case Instruction::GetElementPtr: {
+    const DataLayout &DL = *TM.getDataLayout();
+
+    // Generate a symbolic expression for the byte address
+    APInt OffsetAI(DL.getPointerTypeSizeInBits(CE->getType()), 0);
+    cast<GEPOperator>(CE)->accumulateConstantOffset(DL, OffsetAI);
+
+    const MCExpr *Base = lowerConstantForGV(CE->getOperand(0),
+                                            ProcessingGeneric);
+    if (!OffsetAI)
+      return Base;
+
+    int64_t Offset = OffsetAI.getSExtValue();
+    return MCBinaryExpr::CreateAdd(Base, MCConstantExpr::Create(Offset, Ctx),
+                                   Ctx);
+  }
+
+  case Instruction::Trunc:
+    // We emit the value and depend on the assembler to truncate the generated
+    // expression properly.  This is important for differences between
+    // blockaddress labels.  Since the two labels are in the same function, it
+    // is reasonable to treat their delta as a 32-bit value.
+    // FALL THROUGH.
+  case Instruction::BitCast:
+    return lowerConstantForGV(CE->getOperand(0), ProcessingGeneric);
+
+  case Instruction::IntToPtr: {
+    const DataLayout &DL = *TM.getDataLayout();
+
+    // Handle casts to pointers by changing them into casts to the appropriate
+    // integer type.  This promotes constant folding and simplifies this code.
+    Constant *Op = CE->getOperand(0);
+    Op = ConstantExpr::getIntegerCast(Op, DL.getIntPtrType(CV->getType()),
+                                      false/*ZExt*/);
+    return lowerConstantForGV(Op, ProcessingGeneric);
+  }
+
+  case Instruction::PtrToInt: {
+    const DataLayout &DL = *TM.getDataLayout();
+
+    // Support only foldable casts to/from pointers that can be eliminated by
+    // changing the pointer to the appropriately sized integer type.
+    Constant *Op = CE->getOperand(0);
+    Type *Ty = CE->getType();
+
+    const MCExpr *OpExpr = lowerConstantForGV(Op, ProcessingGeneric);
+
+    // We can emit the pointer value into this slot if the slot is an
+    // integer slot equal to the size of the pointer.
+    if (DL.getTypeAllocSize(Ty) == DL.getTypeAllocSize(Op->getType()))
+      return OpExpr;
+
+    // Otherwise the pointer is smaller than the resultant integer, mask off
+    // the high bits so we are sure to get a proper truncation if the input is
+    // a constant expr.
+    unsigned InBits = DL.getTypeAllocSizeInBits(Op->getType());
+    const MCExpr *MaskExpr = MCConstantExpr::Create(~0ULL >> (64-InBits), Ctx);
+    return MCBinaryExpr::CreateAnd(OpExpr, MaskExpr, Ctx);
+  }
+
+  // The MC library also has a right-shift operator, but it isn't consistently
+  // signed or unsigned between different targets.
+  case Instruction::Add: {
+    const MCExpr *LHS = lowerConstantForGV(CE->getOperand(0), ProcessingGeneric);
+    const MCExpr *RHS = lowerConstantForGV(CE->getOperand(1), ProcessingGeneric);
+    switch (CE->getOpcode()) {
+    default: llvm_unreachable("Unknown binary operator constant cast expr");
+    case Instruction::Add: return MCBinaryExpr::CreateAdd(LHS, RHS, Ctx);
+    }
+  }
+  }
+}
+
+// Copy of MCExpr::print customized for NVPTX
+void NVPTXAsmPrinter::printMCExpr(const MCExpr &Expr, raw_ostream &OS) {
+  switch (Expr.getKind()) {
+  case MCExpr::Target:
+    return cast<MCTargetExpr>(&Expr)->PrintImpl(OS);
+  case MCExpr::Constant:
+    OS << cast<MCConstantExpr>(Expr).getValue();
+    return;
+
+  case MCExpr::SymbolRef: {
+    const MCSymbolRefExpr &SRE = cast<MCSymbolRefExpr>(Expr);
+    const MCSymbol &Sym = SRE.getSymbol();
+    OS << Sym;
+    return;
+  }
+
+  case MCExpr::Unary: {
+    const MCUnaryExpr &UE = cast<MCUnaryExpr>(Expr);
+    switch (UE.getOpcode()) {
+    case MCUnaryExpr::LNot:  OS << '!'; break;
+    case MCUnaryExpr::Minus: OS << '-'; break;
+    case MCUnaryExpr::Not:   OS << '~'; break;
+    case MCUnaryExpr::Plus:  OS << '+'; break;
+    }
+    printMCExpr(*UE.getSubExpr(), OS);
+    return;
+  }
+
+  case MCExpr::Binary: {
+    const MCBinaryExpr &BE = cast<MCBinaryExpr>(Expr);
+
+    // Only print parens around the LHS if it is non-trivial.
+    if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS()) ||
+        isa<NVPTXGenericMCSymbolRefExpr>(BE.getLHS())) {
+      printMCExpr(*BE.getLHS(), OS);
+    } else {
+      OS << '(';
+      printMCExpr(*BE.getLHS(), OS);
+      OS<< ')';
+    }
+
+    switch (BE.getOpcode()) {
+    case MCBinaryExpr::Add:
+      // Print "X-42" instead of "X+-42".
+      if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) {
+        if (RHSC->getValue() < 0) {
+          OS << RHSC->getValue();
+          return;
+        }
+      }
+
+      OS <<  '+';
+      break;
+    default: llvm_unreachable("Unhandled binary operator");
+    }
+
+    // Only print parens around the LHS if it is non-trivial.
+    if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) {
+      printMCExpr(*BE.getRHS(), OS);
+    } else {
+      OS << '(';
+      printMCExpr(*BE.getRHS(), OS);
+      OS << ')';
+    }
+    return;
+  }
+  }
+
+  llvm_unreachable("Invalid expression kind!");
+}
+
 /// PrintAsmOperand - Print out an operand for an inline asm expression.
 ///
 bool NVPTXAsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,

llvm/lib/Target/NVPTX/NVPTXAsmPrinter.h

@@ -169,8 +169,10 @@ class LLVM_LIBRARY_VISIBILITY NVPTXAsmPrinter : public AsmPrinter {
               } else {
                 O << *Name;
               }
-            } else if (const ConstantExpr *Cexpr = dyn_cast<ConstantExpr>(v)) {
-              O << *AP.lowerConstant(Cexpr);
+            } else if (const ConstantExpr *CExpr = dyn_cast<ConstantExpr>(v0)) {
+              const MCExpr *Expr =
+                AP.lowerConstantForGV(cast<Constant>(CExpr), false);
+              AP.printMCExpr(*Expr, O);
             } else
               llvm_unreachable("symbol type unknown");
             nSym++;
@@ -241,6 +243,10 @@ class LLVM_LIBRARY_VISIBILITY NVPTXAsmPrinter : public AsmPrinter {
   bool PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
                              unsigned AsmVariant, const char *ExtraCode,
                              raw_ostream &) override;
+
+  const MCExpr *lowerConstantForGV(const Constant *CV, bool ProcessingGeneric);
+  void printMCExpr(const MCExpr &Expr, raw_ostream &OS);
+
 protected:
   bool doInitialization(Module &M) override;
   bool doFinalization(Module &M) override;

llvm/lib/Target/NVPTX/NVPTXMCExpr.cpp

@@ -45,3 +45,13 @@ void NVPTXFloatMCExpr::PrintImpl(raw_ostream &OS) const {
     OS << std::string(NumHex - HexStr.length(), '0');
   OS << utohexstr(API.getZExtValue());
 }
+
+const NVPTXGenericMCSymbolRefExpr*
+NVPTXGenericMCSymbolRefExpr::Create(const MCSymbolRefExpr *SymExpr,
+                                    MCContext &Ctx) {
+  return new (Ctx) NVPTXGenericMCSymbolRefExpr(SymExpr);
+}
+
+void NVPTXGenericMCSymbolRefExpr::PrintImpl(raw_ostream &OS) const {
+  OS << "generic(" << *SymExpr << ")";
+}

llvm/lib/Target/NVPTX/NVPTXMCExpr.h

@@ -79,6 +79,50 @@ class NVPTXFloatMCExpr : public MCTargetExpr {
     return E->getKind() == MCExpr::Target;
   }
 };
+
+/// A wrapper for MCSymbolRefExpr that tells the assembly printer that the
+/// symbol should be enclosed by generic().
+class NVPTXGenericMCSymbolRefExpr : public MCTargetExpr {
+private:
+  const MCSymbolRefExpr *SymExpr;
+
+  explicit NVPTXGenericMCSymbolRefExpr(const MCSymbolRefExpr *_SymExpr)
+      : SymExpr(_SymExpr) {}
+
+public:
+  /// @name Construction
+  /// @{
+
+  static const NVPTXGenericMCSymbolRefExpr
+  *Create(const MCSymbolRefExpr *SymExpr, MCContext &Ctx);
+
+  /// @}
+  /// @name Accessors
+  /// @{
+
+  /// getOpcode - Get the kind of this expression.
+  const MCSymbolRefExpr *getSymbolExpr() const { return SymExpr; }
+
+  /// @}
+
+  void PrintImpl(raw_ostream &OS) const;
+  bool EvaluateAsRelocatableImpl(MCValue &Res,
+                                 const MCAsmLayout *Layout,
+                                 const MCFixup *Fixup) const override {
+    return false;
+  }
+  void visitUsedExpr(MCStreamer &Streamer) const override {};
+  const MCSection *FindAssociatedSection() const override {
+    return nullptr;
+  }
+
+  // There are no TLS NVPTXMCExprs at the moment.
+  void fixELFSymbolsInTLSFixups(MCAssembler &Asm) const override {}
+
+  static bool classof(const MCExpr *E) {
+    return E->getKind() == MCExpr::Target;
+  }
+  };
 } // end namespace llvm
 
 #endif

llvm/test/CodeGen/NVPTX/addrspacecast-gvar.ll

@@ -4,8 +4,10 @@
 ; CHECK: .visible .global .align 4 .u32 g2 = generic(g);
 ; CHECK: .visible .global .align 4 .u32 g3 = g;
 ; CHECK: .visible .global .align 8 .u32 g4[2] = {0, generic(g)};
+; CHECK: .visible .global .align 8 .u32 g5[2] = {0, generic(g)+8};
 
 @g = addrspace(1) global i32 42
 @g2 = addrspace(1) global i32* addrspacecast (i32 addrspace(1)* @g to i32*)
 @g3 = addrspace(1) global i32 addrspace(1)* @g
 @g4 = constant {i32*, i32*} {i32* null, i32* addrspacecast (i32 addrspace(1)* @g to i32*)}
+@g5 = constant {i32*, i32*} {i32* null, i32* addrspacecast (i32 addrspace(1)* getelementptr (i32, i32 addrspace(1)* @g, i32 2) to i32*)}