[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

1 files changed, 21 insertions, 1 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64MCInstLower.cpp b/llvm/lib/Target/AArch64/AArch64MCInstLower.cpp
index f82b9dbc2c9..f1281a1b912 100644
--- a/llvm/lib/Target/AArch64/AArch64MCInstLower.cpp
+++ b/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 *