Splitstack implementation for android

Author: ILyoan

lib/Target/AArch64/AArch64Subtarget.h

@@ -64,6 +64,9 @@ class AArch64Subtarget : public AArch64GenSubtargetInfo {
 
   bool isTargetELF() const { return TargetTriple.isOSBinFormatELF(); }
   bool isTargetLinux() const { return TargetTriple.isOSLinux(); }
+  bool isTargetAndroid() const {
+    return TargetTriple.getEnvironment() == Triple::Android;
+  }
 
   bool hasFPARMv8() const { return HasFPARMv8; }
   bool hasNEON() const { return HasNEON; }

lib/Target/ARM/ARMFrameLowering.cpp

@@ -14,7 +14,9 @@
 #include "ARMFrameLowering.h"
 #include "ARMBaseInstrInfo.h"
 #include "ARMBaseRegisterInfo.h"
+#include "ARMInstrInfo.h"
 #include "ARMMachineFunctionInfo.h"
+#include "ARMTargetMachine.h"
 #include "MCTargetDesc/ARMAddressingModes.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
@@ -1603,3 +1605,219 @@ eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
   MBB.erase(I);
 }
 
+// Get minimum constant for ARM instruction set that is greator than 
+// or equal to the argument.
+// In ARM instruction, constant can have any value that can be
+// produced by rotating an 8-bit value right by and even number
+// of bits within a 32-bit word.
+static uint32_t AlignToARMConstant(uint32_t Value) {
+  unsigned Shifted = 0;
+
+  if (Value == 0)
+      return 0;
+
+  while (!(Value & 0xC0000000)) {
+      Value = Value << 2;
+      Shifted += 2;
+  }
+
+  bool Carry = (Value & 0x00FFFFFF);
+  Value = ((Value & 0xFF000000) >> 24) + Carry;
+
+  if (Value & 0x0000100)
+      Value = Value & 0x000001FC;
+
+  if (Shifted > 24)
+      Value = Value >> (Shifted - 24);
+  else 
+      Value = Value << (24 - Shifted);
+
+  return Value;
+}
+
+// The stack limit in the TCB is set to this manyu bytes above the actual 
+// stack limit.
+static const uint64_t kSplitStackAvailable = 256;
+
+// Adjust function prologue to enable split stack.
+// Only support android.
+void 
+ARMFrameLowering::adjustForSegmentedStacks(MachineFunction &MF) const {
+  const ARMSubtarget *ST = &MF.getTarget().getSubtarget<ARMSubtarget>();
+
+  // Doesn't support vararg function.
+  if (MF.getFunction()->isVarArg())
+    report_fatal_error("Segmented stacks do not support vararg functions.");
+  // Doesn't support other than android.
+  if (!ST->isTargetAndroid())
+    report_fatal_error("Segmented statks not supported on this platfrom.");
+  
+  MachineBasicBlock &prologueMBB = MF.front();
+  MachineFrameInfo* MFI = MF.getFrameInfo();
+  const ARMBaseInstrInfo &TII = *TM.getInstrInfo();
+  ARMFunctionInfo* ARMFI = MF.getInfo<ARMFunctionInfo>();
+  DebugLoc DL;
+
+  // Use R4 and R5 as scratch register.
+  // We should save R4 and R5 before use it and restore before
+  // leave the function.
+  unsigned ScratchReg0 = ARM::R4;
+  unsigned ScratchReg1 = ARM::R5;
+  // Use the last tls slot.
+  unsigned TlsOffset = 63;
+  uint64_t AlignedStackSize;
+
+  MachineBasicBlock* prevStackMBB = MF.CreateMachineBasicBlock();
+  MachineBasicBlock* postStackMBB = MF.CreateMachineBasicBlock();
+  MachineBasicBlock* allocMBB = MF.CreateMachineBasicBlock();
+  MachineBasicBlock* checkMBB = MF.CreateMachineBasicBlock();
+
+  for (MachineBasicBlock::livein_iterator i = prologueMBB.livein_begin(),
+         e = prologueMBB.livein_end(); i != e; ++i) {
+    allocMBB->addLiveIn(*i);
+    checkMBB->addLiveIn(*i);
+    prevStackMBB->addLiveIn(*i);
+    postStackMBB->addLiveIn(*i);
+  }
+
+  MF.push_front(postStackMBB);
+  MF.push_front(allocMBB);
+  MF.push_front(checkMBB);
+  MF.push_front(prevStackMBB);
+
+  // The required stack size that is aligend to ARM constant critarion.
+  uint64_t StackSize = MFI->getStackSize();
+
+  // If the front-end requested a fixed stack segment size, use that.
+  if (MF.getFunction()->hasFnAttribute("fixedstacksegment")) {
+    StackSize = MF.getTarget().Options.FixedStackSegmentSize;
+  }
+
+  AlignedStackSize = AlignToARMConstant(StackSize)
+
+  // When the frame size is less than 256 we just compare the stack
+  // boundary directly to the value of the stack pointer, per gcc.
+  bool CompareStackPointer = AlignedStackSize < kSplitStackAvailable;
+
+  // We will use two of callee save registers as scratch register so we
+  // need to save those registers into stack frame before use it.
+  // We will use SR0 to hold stack limit and SR1 to stack size requested.
+  // and arguments for __morestack().
+  // SR0: Scratch Register #0
+  // SR1: Scratch Register #1
+  // push {SR0, SR1}
+  AddDefaultPred(BuildMI(prevStackMBB, DL, TII.get(ARM::STMDB_UPD))
+                 .addReg(ARM::SP, RegState::Define)
+                 .addReg(ARM::SP))
+    .addReg(ScratchReg0)
+    .addReg(ScratchReg1);
+
+  if (CompareStackPointer) {
+    // mov SR1, sp
+    AddDefaultPred(BuildMI(checkMBB, DL, TII.get(ARM::MOVr), ScratchReg1)
+                   .addReg(ARM::SP)).addReg(0);
+  } else {
+    // sub SR1, sp, #StackSize
+    AddDefaultPred(BuildMI(checkMBB, DL, TII.get(ARM::SUBri), ScratchReg1)
+                   .addReg(ARM::SP).addImm(AlignedStackSize)).addReg(0);
+  }
+ 
+  // Get TLS base address.
+  // mrc p15, #0, SR0, c13, c0, #3
+  AddDefaultPred(BuildMI(checkMBB, DL, TII.get(ARM::MRC), ScratchReg0)
+                 .addImm(15)
+                 .addImm(0)
+                 .addImm(13)
+                 .addImm(0)
+                 .addImm(3));
+
+  // The last slot, assume that the last tls slot holds the stack limit
+  // add SR0, SR0, #252
+  AddDefaultPred(BuildMI(checkMBB, DL, TII.get(ARM::ADDri), ScratchReg0)
+                 .addReg(ScratchReg0).addImm(4*TlsOffset)).addReg(0);
+
+  // Get stack limit.
+  // ldr SR0, [sr0]
+  AddDefaultPred(BuildMI(checkMBB, DL, TII.get(ARM::LDRi12), ScratchReg0)
+                 .addReg(ScratchReg0).addImm(0));
+
+  // Compare stack limit with stack size requested.
+  // cmp SR0, SR1
+  AddDefaultPred(BuildMI(checkMBB, DL, TII.get(ARM::CMPrr))
+                 .addReg(ScratchReg0)
+                 .addReg(ScratchReg1));
+
+  // This jump is taken if StackLimit < SP - stack required.
+  BuildMI(checkMBB, DL, TII.get(ARM::Bcc)).addMBB(postStackMBB)
+    .addImm(ARMCC::LO)
+    .addReg(ARM::CPSR);
+
+
+  // Calling __morestack(StackSize, Size of stack arguments).
+  // __morestack knows that the stack size requested is in SR0(r4)
+  // and amount size of stack arguments is in SR1(r5).
+
+  // Pass first argument for the __morestack by Scratch Register #0.
+  //   The amount size of stack required
+  AddDefaultPred(BuildMI(allocMBB, DL, TII.get(ARM::MOVi), ScratchReg0)
+                 .addImm(AlignedStackSize)).addReg(0);
+  // Pass second argument for the __morestack by Scratch Register #1.
+  //   The amount size of stack consumed to save function arguments.
+  AddDefaultPred(BuildMI(allocMBB, DL, TII.get(ARM::MOVi), ScratchReg1)
+                 .addImm(AlignToARMConstant(ARMFI->getArgumentStackSize())))
+                 .addReg(0);
+
+  // push {lr} - Save return address of this function.
+  AddDefaultPred(BuildMI(allocMBB, DL, TII.get(ARM::STMDB_UPD))
+                 .addReg(ARM::SP, RegState::Define)
+                 .addReg(ARM::SP))
+    .addReg(ARM::LR);
+
+  // Call __morestack().
+  BuildMI(allocMBB, DL, TII.get(ARM::BL))
+    .addExternalSymbol("__morestack");
+  
+  // Restore return address of this original function.
+  // pop {lr}
+  AddDefaultPred(BuildMI(allocMBB, DL, TII.get(ARM::LDMIA_UPD))
+                 .addReg(ARM::SP, RegState::Define)
+                 .addReg(ARM::SP))
+    .addReg(ARM::LR);
+
+
+  // Restore SR0 and SR1 in case of __morestack() was called.
+  // __morestack() will skip postStackMBB block so we need to restore
+  // scratch registers from here.
+  // pop {SR0, SR1}
+  AddDefaultPred(BuildMI(allocMBB, DL, TII.get(ARM::LDMIA_UPD))
+                 .addReg(ARM::SP, RegState::Define)
+                 .addReg(ARM::SP))
+    .addReg(ScratchReg0)
+    .addReg(ScratchReg1);
+
+  // Return from this function.
+  AddDefaultPred(BuildMI(allocMBB, DL, TII.get(ARM::MOVr), ARM::PC)
+                 .addReg(ARM::LR)).addReg(0);
+
+  // Restore SR0 and SR1 in case of __morestack() was not called.
+  // pop {SR0, SR1}
+  AddDefaultPred(BuildMI(postStackMBB, DL, TII.get(ARM::LDMIA_UPD))
+                 .addReg(ARM::SP, RegState::Define)
+                 .addReg(ARM::SP))
+    .addReg(ScratchReg0)
+    .addReg(ScratchReg1);
+
+  // Organizing MBB lists
+  postStackMBB->addSuccessor(&prologueMBB);
+
+  allocMBB->addSuccessor(postStackMBB);
+  
+  checkMBB->addSuccessor(postStackMBB);
+  checkMBB->addSuccessor(allocMBB);
+  
+  prevStackMBB->addSuccessor(checkMBB);
+
+#ifdef XDEBUG
+  MF.verify();
+#endif
+}

lib/Target/ARM/ARMFrameLowering.h

@@ -23,12 +23,14 @@ namespace llvm {
 
 class ARMFrameLowering : public TargetFrameLowering {
 protected:
+  const ARMBaseTargetMachine &TM;
   const ARMSubtarget &STI;
 
 public:
-  explicit ARMFrameLowering(const ARMSubtarget &sti)
+  explicit ARMFrameLowering(const ARMBaseTargetMachine& tm,
+                            const ARMSubtarget &sti)
     : TargetFrameLowering(StackGrowsDown, sti.getStackAlignment(), 0, 4),
-      STI(sti) {
+      TM(tm), STI(sti) {
   }
 
   /// emitProlog/emitEpilog - These methods insert prolog and epilog code into
@@ -59,6 +61,8 @@ class ARMFrameLowering : public TargetFrameLowering {
   void processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
                                             RegScavenger *RS) const;
 
+  void adjustForSegmentedStacks(MachineFunction &MF) const;
+
  private:
   void emitPushInst(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
                     const std::vector<CalleeSavedInfo> &CSI, unsigned StmOpc,

lib/Target/ARM/ARMISelLowering.cpp

@@ -3060,6 +3060,8 @@ ARMTargetLowering::LowerFormalArguments(SDValue Chain,
     VarArgStyleRegisters(CCInfo, DAG, dl, Chain,
                          CCInfo.getNextStackOffset());
 
+  AFI->setArgumentStackSize(CCInfo.getNextStackOffset());
+
   return Chain;
 }
 

lib/Target/ARM/ARMMachineFunctionInfo.h

@@ -114,6 +114,10 @@ class ARMFunctionInfo : public MachineFunctionInfo {
   /// relocation models.
   unsigned GlobalBaseReg;
 
+  /// ArgumentStackSize - amount of bytes on stack consumed by the arguments
+  /// being passed on the stack
+  unsigned ArgumentStackSize;
+
 public:
   ARMFunctionInfo() :
     isThumb(false),
@@ -182,6 +186,9 @@ class ARMFunctionInfo : public MachineFunctionInfo {
   void setGPRCalleeSavedArea2Size(unsigned s) { GPRCS2Size = s; }
   void setDPRCalleeSavedAreaSize(unsigned s)  { DPRCSSize = s; }
 
+  unsigned getArgumentStackSize() const { return ArgumentStackSize; }
+  void setArgumentStackSize(unsigned size) { ArgumentStackSize = size; }
+
   unsigned createJumpTableUId() {
     return JumpTableUId++;
   }

lib/Target/ARM/ARMSubtarget.h

@@ -346,6 +346,9 @@ class ARMSubtarget : public ARMGenSubtargetInfo {
     return TargetTriple.getEnvironment() == Triple::GNUEABIHF ||
            TargetTriple.getEnvironment() == Triple::EABIHF;
   }
+  bool isTargetAndroid() const {
+    return TargetTriple.getEnvironment() == Triple::Android;
+  }
 
   bool isAPCS_ABI() const {
     assert(TargetABI != ARM_ABI_UNKNOWN);

lib/Target/ARM/ARMTargetMachine.cpp

@@ -124,7 +124,7 @@ ARMTargetMachine::ARMTargetMachine(const Target &T, StringRef TT,
     DL(computeDataLayout(Subtarget)),
     TLInfo(*this),
     TSInfo(*this),
-    FrameLowering(Subtarget) {
+    FrameLowering(*this, Subtarget) {
   initAsmInfo();
   if (!Subtarget.hasARMOps())
     report_fatal_error("CPU: '" + Subtarget.getCPUString() + "' does not "
@@ -146,8 +146,8 @@ ThumbTargetMachine::ThumbTargetMachine(const Target &T, StringRef TT,
     TLInfo(*this),
     TSInfo(*this),
     FrameLowering(Subtarget.hasThumb2()
-              ? new ARMFrameLowering(Subtarget)
-              : (ARMFrameLowering*)new Thumb1FrameLowering(Subtarget)) {
+              ? new ARMFrameLowering(*this, Subtarget)
+              : (ARMFrameLowering*)new Thumb1FrameLowering(*this, Subtarget)) {
   initAsmInfo();
 }
 

lib/Target/ARM/ARMTargetMachine.h

@@ -61,6 +61,10 @@ class ARMBaseTargetMachine : public LLVMTargetMachine {
   virtual TargetPassConfig *createPassConfig(PassManagerBase &PM);
 
   virtual bool addCodeEmitter(PassManagerBase &PM, JITCodeEmitter &MCE);
+
+  virtual const ARMBaseInstrInfo *getInstrInfo() const {
+    llvm_unreachable("getInstrInfo not implemented");
+  }
 };
 
 /// ARMTargetMachine - ARM target machine.

lib/Target/ARM/Thumb1FrameLowering.h

@@ -22,12 +22,14 @@
 #include "llvm/Target/TargetFrameLowering.h"
 
 namespace llvm {
+  class ARMBaseTargetMachine;
   class ARMSubtarget;
 
 class Thumb1FrameLowering : public ARMFrameLowering {
 public:
-  explicit Thumb1FrameLowering(const ARMSubtarget &sti)
-    : ARMFrameLowering(sti) {
+  explicit Thumb1FrameLowering(const ARMBaseTargetMachine &tm,
+                               const ARMSubtarget &sti)
+    : ARMFrameLowering(tm, sti) {
   }
 
   /// emitProlog/emitEpilog - These methods insert prolog and epilog code into