[AArch64] Add support for dllimport of values and functions

Previously, the dllimport attribute did the right thing in terms
of treating it as a pointer to a value, but this makes sure the
names get mangled properly, and calls to such functions load the
function from the __imp_ pointer.

This is based on SVN r212431 and r212430 where the same was
implemented for ARM.

Differential Revision: https://reviews.llvm.org/D38530

llvm-svn: 316555

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -3487,6 +3487,10 @@ AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
         AArch64II::MO_GOT) {
       Callee = DAG.getTargetGlobalAddress(GV, DL, PtrVT, 0, AArch64II::MO_GOT);
       Callee = DAG.getNode(AArch64ISD::LOADgot, DL, PtrVT, Callee);
+    } else if (Subtarget->isTargetCOFF() && GV->hasDLLImportStorageClass()) {
+      assert(Subtarget->isTargetWindows() &&
+             "Windows is the only supported COFF target");
+      Callee = getGOT(G, DAG, AArch64II::MO_DLLIMPORT);
     } else {
       const GlobalValue *GV = G->getGlobal();
       Callee = DAG.getTargetGlobalAddress(GV, DL, PtrVT, 0, 0);
@@ -3687,11 +3691,12 @@ SDValue AArch64TargetLowering::getTargetNode(BlockAddressSDNode* N, EVT Ty,
 
 // (loadGOT sym)
 template <class NodeTy>
-SDValue AArch64TargetLowering::getGOT(NodeTy *N, SelectionDAG &DAG) const {
+SDValue AArch64TargetLowering::getGOT(NodeTy *N, SelectionDAG &DAG,
+                                      unsigned Flags) const {
   DEBUG(dbgs() << "AArch64TargetLowering::getGOT\n");
   SDLoc DL(N);
   EVT Ty = getPointerTy(DAG.getDataLayout());
-  SDValue GotAddr = getTargetNode(N, Ty, DAG, AArch64II::MO_GOT);
+  SDValue GotAddr = getTargetNode(N, Ty, DAG, AArch64II::MO_GOT | Flags);
   // FIXME: Once remat is capable of dealing with instructions with register
   // operands, expand this into two nodes instead of using a wrapper node.
   return DAG.getNode(AArch64ISD::LOADgot, DL, Ty, GotAddr);
@@ -3699,29 +3704,30 @@ SDValue AArch64TargetLowering::getGOT(NodeTy *N, SelectionDAG &DAG) const {
 
 // (wrapper %highest(sym), %higher(sym), %hi(sym), %lo(sym))
 template <class NodeTy>
-SDValue AArch64TargetLowering::getAddrLarge(NodeTy *N, SelectionDAG &DAG)
-  const {
+SDValue AArch64TargetLowering::getAddrLarge(NodeTy *N, SelectionDAG &DAG,
+                                            unsigned Flags) const {
   DEBUG(dbgs() << "AArch64TargetLowering::getAddrLarge\n");
   SDLoc DL(N);
   EVT Ty = getPointerTy(DAG.getDataLayout());
   const unsigned char MO_NC = AArch64II::MO_NC;
   return DAG.getNode(
       AArch64ISD::WrapperLarge, DL, Ty,
-        getTargetNode(N, Ty, DAG, AArch64II::MO_G3),
-        getTargetNode(N, Ty, DAG, AArch64II::MO_G2 | MO_NC),
-        getTargetNode(N, Ty, DAG, AArch64II::MO_G1 | MO_NC),
-        getTargetNode(N, Ty, DAG, AArch64II::MO_G0 | MO_NC));
+      getTargetNode(N, Ty, DAG, AArch64II::MO_G3 | Flags),
+      getTargetNode(N, Ty, DAG, AArch64II::MO_G2 | MO_NC | Flags),
+      getTargetNode(N, Ty, DAG, AArch64II::MO_G1 | MO_NC | Flags),
+      getTargetNode(N, Ty, DAG, AArch64II::MO_G0 | MO_NC | Flags));
 }
 
 // (addlow (adrp %hi(sym)) %lo(sym))
 template <class NodeTy>
-SDValue AArch64TargetLowering::getAddr(NodeTy *N, SelectionDAG &DAG) const {
+SDValue AArch64TargetLowering::getAddr(NodeTy *N, SelectionDAG &DAG,
+                                       unsigned Flags) const {
   DEBUG(dbgs() << "AArch64TargetLowering::getAddr\n");
   SDLoc DL(N);
   EVT Ty = getPointerTy(DAG.getDataLayout());
-  SDValue Hi = getTargetNode(N, Ty, DAG, AArch64II::MO_PAGE);
+  SDValue Hi = getTargetNode(N, Ty, DAG, AArch64II::MO_PAGE | Flags);
   SDValue Lo = getTargetNode(N, Ty, DAG,
-                             AArch64II::MO_PAGEOFF | AArch64II::MO_NC);
+                             AArch64II::MO_PAGEOFF | AArch64II::MO_NC | Flags);
   SDValue ADRP = DAG.getNode(AArch64ISD::ADRP, DL, Ty, Hi);
   return DAG.getNode(AArch64ISD::ADDlow, DL, Ty, ADRP, Lo);
 }
@@ -3730,6 +3736,9 @@ SDValue AArch64TargetLowering::LowerGlobalAddress(SDValue Op,
                                                   SelectionDAG &DAG) const {
   GlobalAddressSDNode *GN = cast<GlobalAddressSDNode>(Op);
   const GlobalValue *GV = GN->getGlobal();
+  const AArch64II::TOF TargetFlags =
+      (GV->hasDLLImportStorageClass() ? AArch64II::MO_DLLIMPORT
+                                      : AArch64II::MO_NO_FLAG);
   unsigned char OpFlags =
       Subtarget->ClassifyGlobalReference(GV, getTargetMachine());
 
@@ -3738,14 +3747,21 @@ SDValue AArch64TargetLowering::LowerGlobalAddress(SDValue Op,
 
   // This also catches the large code model case for Darwin.
   if ((OpFlags & AArch64II::MO_GOT) != 0) {
-    return getGOT(GN, DAG);
+    return getGOT(GN, DAG, TargetFlags);
   }
 
+  SDValue Result;
   if (getTargetMachine().getCodeModel() == CodeModel::Large) {
-    return getAddrLarge(GN, DAG);
+    Result = getAddrLarge(GN, DAG, TargetFlags);
   } else {
-    return getAddr(GN, DAG);
+    Result = getAddr(GN, DAG, TargetFlags);
   }
+  EVT PtrVT = getPointerTy(DAG.getDataLayout());
+  SDLoc DL(GN);
+  if (GV->hasDLLImportStorageClass())
+    Result = DAG.getLoad(PtrVT, DL, DAG.getEntryNode(), Result,
+                         MachinePointerInfo::getGOT(DAG.getMachineFunction()));
+  return Result;
 }
 
 /// \brief Convert a TLS address reference into the correct sequence of loads

llvm/lib/Target/AArch64/AArch64ISelLowering.h

@@ -538,10 +538,12 @@ private:
                         unsigned Flag) const;
   SDValue getTargetNode(BlockAddressSDNode *N, EVT Ty, SelectionDAG &DAG,
                         unsigned Flag) const;
-  template <class NodeTy> SDValue getGOT(NodeTy *N, SelectionDAG &DAG) const;
   template <class NodeTy>
-  SDValue getAddrLarge(NodeTy *N, SelectionDAG &DAG) const;
-  template <class NodeTy> SDValue getAddr(NodeTy *N, SelectionDAG &DAG) const;
+  SDValue getGOT(NodeTy *N, SelectionDAG &DAG, unsigned Flags = 0) const;
+  template <class NodeTy>
+  SDValue getAddrLarge(NodeTy *N, SelectionDAG &DAG, unsigned Flags = 0) const;
+  template <class NodeTy>
+  SDValue getAddr(NodeTy *N, SelectionDAG &DAG, unsigned Flags = 0) const;
   SDValue LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerDarwinGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const;

llvm/lib/Target/AArch64/AArch64MCInstLower.cpp

@@ -19,10 +19,12 @@
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineInstr.h"
 #include "llvm/IR/Mangler.h"
+#include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/CommandLine.h"
+#include "llvm/Target/TargetLoweringObjectFile.h"
 #include "llvm/Target/TargetMachine.h"
 using namespace llvm;
 
@@ -33,7 +35,25 @@ AArch64MCInstLower::AArch64MCInstLower(MCContext &ctx, AsmPrinter &printer)
 
 MCSymbol *
 AArch64MCInstLower::GetGlobalAddressSymbol(const MachineOperand &MO) const {
-  return Printer.getSymbol(MO.getGlobal());
+  const GlobalValue *GV = MO.getGlobal();
+  unsigned TargetFlags = MO.getTargetFlags();
+  const Triple &TheTriple = Printer.TM.getTargetTriple();
+  if (!TheTriple.isOSBinFormatCOFF())
+    return Printer.getSymbol(GV);
+
+  assert(TheTriple.isOSWindows() &&
+         "Windows is the only supported COFF target");
+
+  bool IsIndirect = (TargetFlags & AArch64II::MO_DLLIMPORT);
+  if (!IsIndirect)
+    return Printer.getSymbol(GV);
+
+  SmallString<128> Name;
+  Name = "__imp_";
+  Printer.TM.getNameWithPrefix(Name, GV,
+                               Printer.getObjFileLowering().getMangler());
+
+  return Ctx.getOrCreateSymbol(Name);
 }
 
 MCSymbol *

llvm/lib/Target/AArch64/Utils/AArch64BaseInfo.h

@@ -517,7 +517,12 @@ namespace AArch64II {
     /// thread-local symbol. On Darwin, only one type of thread-local access
     /// exists (pre linker-relaxation), but on ELF the TLSModel used for the
     /// referee will affect interpretation.
-    MO_TLS = 0x40
+    MO_TLS = 0x40,
+
+    /// MO_DLLIMPORT - On a symbol operand, this represents that the reference
+    /// to the symbol is for an import stub.  This is used for DLL import
+    /// storage class indication on Windows.
+    MO_DLLIMPORT = 0x80,
   };
 } // end namespace AArch64II
 

llvm/test/CodeGen/AArch64/dllimport.ll

@@ -0,0 +1,54 @@
+; RUN: llc -mtriple aarch64-unknown-windows-msvc -filetype asm -o - %s | FileCheck %s
+
+@var = external dllimport global i32
+@ext = external global i32
+declare dllimport i32 @external()
+declare i32 @internal()
+
+define i32 @get_var() {
+  %1 = load i32, i32* @var, align 4
+  ret i32 %1
+}
+
+; CHECK-LABEL: get_var
+; CHECK: adrp x8, __imp_var
+; CHECK: ldr x8, [x8, __imp_var]
+; CHECK: ldr w0, [x8]
+; CHECK: ret
+
+define i32 @get_ext() {
+  %1 = load i32, i32* @ext, align 4
+  ret i32 %1
+}
+
+; CHECK-LABEL: get_ext
+; CHECK: adrp x8, ext
+; CHECK: ldr w0, [x8, ext]
+; CHECK: ret
+
+define i32* @get_var_pointer() {
+  ret i32* @var
+}
+
+; CHECK-LABEL: get_var_pointer
+; CHECK: adrp x0, __imp_var
+; CHECK: ldr x0, [x0, __imp_var]
+; CHECK: ret
+
+define i32 @call_external() {
+  %call = tail call i32 @external()
+  ret i32 %call
+}
+
+; CHECK-LABEL: call_external
+; CHECK: adrp x0, __imp_external
+; CHECK: ldr x0, [x0, __imp_external]
+; CHECK: br x0
+
+define i32 @call_internal() {
+  %call = tail call i32 @internal()
+  ret i32 %call
+}
+
+; CHECK-LABEL: call_internal
+; CHECK: b internal