" needed for the function."),
cl::init(false), cl::Hidden);
+cl::opt<bool>
+EnableBasePointer("x86-use-base-pointer", cl::Hidden, cl::init(true),
+ cl::desc("Enable use of a base pointer for complex stack frames"));
+
X86RegisterInfo::X86RegisterInfo(X86TargetMachine &tm,
const TargetInstrInfo &tii)
: X86GenRegisterInfo(tm.getSubtarget<X86Subtarget>().is64Bit()
SlotSize = 8;
StackPtr = X86::RSP;
FramePtr = X86::RBP;
+ BasePtr = X86::RBX;
} else {
SlotSize = 4;
StackPtr = X86::ESP;
FramePtr = X86::EBP;
+ BasePtr = X86::EBX;
}
}
Reserved.set(*I);
}
+ // Set the base-pointer register and its aliases as reserved if needed.
+ if (hasBasePointer(MF)) {
+ CallingConv::ID CC = MF.getFunction()->getCallingConv();
+ const uint32_t* RegMask = getCallPreservedMask(CC);
+ if (MachineOperand::clobbersPhysReg(RegMask, getBaseRegister()))
+ report_fatal_error(
+ "Stack realignment in presence of dynamic allocas is not supported with"
+ "this calling convention.");
+
+ Reserved.set(getBaseRegister());
+ for (MCSubRegIterator I(getBaseRegister(), this); I.isValid(); ++I)
+ Reserved.set(*I);
+ }
+
// Mark the segment registers as reserved.
Reserved.set(X86::CS);
Reserved.set(X86::SS);
// Stack Frame Processing methods
//===----------------------------------------------------------------------===//
+bool X86RegisterInfo::hasBasePointer(const MachineFunction &MF) const {
+ const MachineFrameInfo *MFI = MF.getFrameInfo();
+
+ if (!EnableBasePointer)
+ return false;
+
+ // When we need stack realignment and there are dynamic allocas, we can't
+ // reference off of the stack pointer, so we reserve a base pointer.
+ if (needsStackRealignment(MF) && MFI->hasVarSizedObjects())
+ return true;
+
+ return false;
+}
+
bool X86RegisterInfo::canRealignStack(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
- return (MF.getTarget().Options.RealignStack &&
- !MFI->hasVarSizedObjects());
+ const MachineRegisterInfo *MRI = &MF.getRegInfo();
+ if (!MF.getTarget().Options.RealignStack)
+ return false;
+
+ // Stack realignment requires a frame pointer. If we already started
+ // register allocation with frame pointer elimination, it is too late now.
+ if (!MRI->canReserveReg(FramePtr))
+ return false;
+
+ // If base pointer is necessary. Check that it isn't too late to reserve it.
+ if (MFI->hasVarSizedObjects())
+ return MRI->canReserveReg(BasePtr);
+ return true;
}
bool X86RegisterInfo::needsStackRealignment(const MachineFunction &MF) const {
bool requiresRealignment = ((MFI->getMaxAlignment() > StackAlign) ||
F->hasFnAttr(Attribute::StackAlignment));
- // FIXME: Currently we don't support stack realignment for functions with
- // variable-sized allocas.
- // FIXME: It's more complicated than this...
- if (0 && requiresRealignment && MFI->hasVarSizedObjects())
- report_fatal_error(
- "Stack realignment in presence of dynamic allocas is not supported");
-
// If we've requested that we force align the stack do so now.
if (ForceStackAlign)
return canRealignStack(MF);
unsigned Opc = MI.getOpcode();
bool AfterFPPop = Opc == X86::TAILJMPm64 || Opc == X86::TAILJMPm;
- if (needsStackRealignment(MF))
+ if (hasBasePointer(MF))
+ BasePtr = getBaseRegister();
+ else if (needsStackRealignment(MF))
BasePtr = (FrameIndex < 0 ? FramePtr : StackPtr);
else if (AfterFPPop)
BasePtr = StackPtr;