[arm-fast-isel] Add support for ELF PIC.

This is a preliminary step towards ELF support; currently ARMFastISel hasn't
been used for ELF object files yet.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164759 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 45 insertions, 0 deletions

diff --git a/lib/Target/ARM/ARMFastISel.cpp b/lib/Target/ARM/ARMFastISel.cpp
index f7f6b5dbb1..8933a02701 100644
--- a/lib/Target/ARM/ARMFastISel.cpp
+++ b/lib/Target/ARM/ARMFastISel.cpp
@@ -194,6 +194,7 @@ class ARMFastISel : public FastISel {
     unsigned ARMMoveToFPReg(EVT VT, unsigned SrcReg);
     unsigned ARMMoveToIntReg(EVT VT, unsigned SrcReg);
     unsigned ARMSelectCallOp(bool UseReg);
+    unsigned ARMLowerPICELF(const GlobalValue *GV, unsigned Align, EVT VT);
 
     // Call handling routines.
   private:
@@ -648,6 +649,9 @@ unsigned ARMFastISel::ARMMaterializeGV(const GlobalValue *GV, EVT VT) {
       Align = TD.getTypeAllocSize(GV->getType());
     }
 
+    if (Subtarget->isTargetELF() && RelocM == Reloc::PIC_)
+      return ARMLowerPICELF(GV, Align, VT);
+
     // Grab index.
     unsigned PCAdj = (RelocM != Reloc::PIC_) ? 0 :
       (Subtarget->isThumb() ? 4 : 8);
@@ -2796,6 +2800,47 @@ bool ARMFastISel::TryToFoldLoad(MachineInstr *MI, unsigned OpNo,
   return true;
 }
 
+unsigned ARMFastISel::ARMLowerPICELF(const GlobalValue *GV,
+                                     unsigned Align, EVT VT) {
+  bool UseGOTOFF = GV->hasLocalLinkage() || GV->hasHiddenVisibility();
+  ARMConstantPoolConstant *CPV =
+    ARMConstantPoolConstant::Create(GV, UseGOTOFF ? ARMCP::GOTOFF : ARMCP::GOT);
+  unsigned Idx = MCP.getConstantPoolIndex(CPV, Align);
+
+  unsigned Opc;
+  unsigned DestReg1 = createResultReg(TLI.getRegClassFor(VT));
+  // Load value.
+  if (isThumb2) {
+    AddOptionalDefs(BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL,
+                            TII.get(ARM::t2LDRpci), DestReg1)
+                    .addConstantPoolIndex(Idx));
+    Opc = UseGOTOFF ? ARM::t2ADDrr : ARM::t2LDRs;
+  } else {
+    // The extra immediate is for addrmode2.
+    AddOptionalDefs(BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt,
+                            DL, TII.get(ARM::LDRcp), DestReg1)
+                    .addConstantPoolIndex(Idx).addImm(0));
+    Opc = UseGOTOFF ? ARM::ADDrr : ARM::LDRrs;
+  }
+
+  unsigned GlobalBaseReg = AFI->getGlobalBaseReg();
+  if (GlobalBaseReg == 0) {
+    GlobalBaseReg = MRI.createVirtualRegister(TLI.getRegClassFor(VT));
+    AFI->setGlobalBaseReg(GlobalBaseReg);
+  }
+
+  unsigned DestReg2 = createResultReg(TLI.getRegClassFor(VT));
+  MachineInstrBuilder MIB = BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt,
+                                    DL, TII.get(Opc), DestReg2)
+                            .addReg(DestReg1)
+                            .addReg(GlobalBaseReg);
+  if (!UseGOTOFF)
+    MIB.addImm(0);
+  AddOptionalDefs(MIB);
+
+  return DestReg2;
+}
+
 namespace llvm {
   FastISel *ARM::createFastISel(FunctionLoweringInfo &funcInfo,
                                 const TargetLibraryInfo *libInfo) {