//===-- PrologEpilogInserter.cpp - Insert Prolog/Epilog code in function --===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
//
// This pass is responsible for finalizing the functions frame layout, saving
// callee saved registers, and for emitting prolog & epilog code for the
#include "llvm/Target/MRegisterInfo.h"
#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
+using namespace llvm;
namespace {
struct PEI : public MachineFunctionPass {
// code for any caller saved registers that are modified. Also calculate
// the MaxCallFrameSize and HasCalls variables for the function's frame
// information and eliminates call frame pseudo instructions.
+ calculateCallerSavedRegisters(Fn);
+
+ // Add the code to save and restore the caller saved registers
saveCallerSavedRegisters(Fn);
// Allow the target machine to make final modifications to the function
// Calculate actual frame offsets for all of the abstract stack objects...
calculateFrameObjectOffsets(Fn);
- // Add prolog and epilog code to the function.
+ // Add prolog and epilog code to the function. This function is required
+ // to align the stack frame as necessary for any stack variables or
+ // called functions. Because of this, calculateCallerSavedRegisters
+ // must be called before this function in order to set the HasCalls
+ // and MaxCallFrameSize variables.
insertPrologEpilogCode(Fn);
// Replace all MO_FrameIndex operands with physical register references
// and actual offsets.
//
replaceFrameIndices(Fn);
+
+ RegsToSave.clear();
+ StackSlots.clear();
return true;
}
private:
+ std::vector<unsigned> RegsToSave;
+ std::vector<int> StackSlots;
+
+ void calculateCallerSavedRegisters(MachineFunction &Fn);
void saveCallerSavedRegisters(MachineFunction &Fn);
void calculateFrameObjectOffsets(MachineFunction &Fn);
void replaceFrameIndices(MachineFunction &Fn);
};
}
+
/// createPrologEpilogCodeInserter - This function returns a pass that inserts
/// prolog and epilog code, and eliminates abstract frame references.
///
-Pass *createPrologEpilogCodeInserter() { return new PEI(); }
+FunctionPass *llvm::createPrologEpilogCodeInserter() { return new PEI(); }
-/// saveCallerSavedRegisters - Scan the function for modified caller saved
-/// registers and insert spill code for any caller saved registers that are
-/// modified. Also calculate the MaxCallFrameSize and HasCalls variables for
+/// calculateCallerSavedRegisters - Scan the function for modified caller saved
+/// registers. Also calculate the MaxCallFrameSize and HasCalls variables for
/// the function's frame information and eliminates call frame pseudo
/// instructions.
///
-void PEI::saveCallerSavedRegisters(MachineFunction &Fn) {
+void PEI::calculateCallerSavedRegisters(MachineFunction &Fn) {
const MRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
- const TargetFrameInfo &FrameInfo = Fn.getTarget().getFrameInfo();
+ const TargetFrameInfo *TFI = Fn.getTarget().getFrameInfo();
// Get the callee saved register list...
const unsigned *CSRegs = RegInfo->getCalleeSaveRegs();
return;
// This bitset contains an entry for each physical register for the target...
- std::vector<bool> ModifiedRegs(MRegisterInfo::FirstVirtualRegister);
+ std::vector<bool> ModifiedRegs(RegInfo->getNumRegs());
unsigned MaxCallFrameSize = 0;
bool HasCalls = false;
for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); )
- if ((*I)->getOpcode() == FrameSetupOpcode ||
- (*I)->getOpcode() == FrameDestroyOpcode) {
- assert((*I)->getNumOperands() == 1 && "Call Frame Setup/Destroy Pseudo"
- " instructions should have a single immediate argument!");
- unsigned Size = (*I)->getOperand(0).getImmedValue();
- if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
- HasCalls = true;
- RegInfo->eliminateCallFramePseudoInstr(Fn, *BB, I);
+ if (I->getOpcode() == FrameSetupOpcode ||
+ I->getOpcode() == FrameDestroyOpcode) {
+ assert(I->getNumOperands() == 1 && "Call Frame Setup/Destroy Pseudo"
+ " instructions should have a single immediate argument!");
+ unsigned Size = I->getOperand(0).getImmedValue();
+ if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
+ HasCalls = true;
+ RegInfo->eliminateCallFramePseudoInstr(Fn, *BB, I++);
} else {
- for (unsigned i = 0, e = (*I)->getNumOperands(); i != e; ++i) {
- MachineOperand &MO = (*I)->getOperand(i);
- assert(!MO.isVirtualRegister() &&
- "Register allocation must be performed!");
- if (MO.isPhysicalRegister() && MO.opIsDef())
- ModifiedRegs[MO.getReg()] = true; // Register is modified
- }
- ++I;
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = I->getOperand(i);
+ if (MO.isRegister() && MO.isDef()) {
+ assert(MRegisterInfo::isPhysicalRegister(MO.getReg()) &&
+ "Register allocation must be performed!");
+ ModifiedRegs[MO.getReg()] = true; // Register is modified
+ }
+ }
+ ++I;
}
MachineFrameInfo *FFI = Fn.getFrameInfo();
// Now figure out which *callee saved* registers are modified by the current
// function, thus needing to be saved and restored in the prolog/epilog.
//
- std::vector<unsigned> RegsToSave;
for (unsigned i = 0; CSRegs[i]; ++i) {
unsigned Reg = CSRegs[i];
if (ModifiedRegs[Reg]) {
RegsToSave.push_back(Reg); // If modified register...
- } else if (const unsigned *AliasSet = RegInfo->getAliasSet(Reg))
- for (unsigned j = 0; AliasSet[j]; ++j) // Check alias registers too...
- if (ModifiedRegs[AliasSet[j]]) {
- RegsToSave.push_back(Reg);
- break;
- }
+ } else {
+ for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
+ *AliasSet; ++AliasSet) { // Check alias registers too...
+ if (ModifiedRegs[*AliasSet]) {
+ RegsToSave.push_back(Reg);
+ break;
+ }
+ }
+ }
}
if (RegsToSave.empty())
return; // Early exit if no caller saved registers are modified!
+ unsigned NumFixedSpillSlots;
+ const std::pair<unsigned,int> *FixedSpillSlots =
+ TFI->getCalleeSaveSpillSlots(NumFixedSpillSlots);
+
// Now that we know which registers need to be saved and restored, allocate
// stack slots for them.
- std::vector<int> StackSlots;
for (unsigned i = 0, e = RegsToSave.size(); i != e; ++i) {
- int FrameIdx = FFI->CreateStackObject(RegInfo->getRegClass(RegsToSave[i]));
+ unsigned Reg = RegsToSave[i];
+
+ // Check to see if this physreg must be spilled to a particular stack slot
+ // on this target.
+ const std::pair<unsigned,int> *FixedSlot = FixedSpillSlots;
+ while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots &&
+ FixedSlot->first != Reg)
+ ++FixedSlot;
+
+ int FrameIdx;
+ if (FixedSlot == FixedSpillSlots+NumFixedSpillSlots) {
+ // Nope, just spill it anywhere convenient.
+ FrameIdx = FFI->CreateStackObject(RegInfo->getSpillSize(Reg)/8,
+ RegInfo->getSpillAlignment(Reg)/8);
+ } else {
+ // Spill it to the stack where we must.
+ FrameIdx = FFI->CreateFixedObject(RegInfo->getSpillSize(Reg)/8,
+ FixedSlot->second);
+ }
StackSlots.push_back(FrameIdx);
}
+}
+
+/// saveCallerSavedRegisters - Insert spill code for any caller saved registers
+/// that are modified in the function.
+///
+void PEI::saveCallerSavedRegisters(MachineFunction &Fn) {
+ // Early exit if no caller saved registers are modified!
+ if (RegsToSave.empty())
+ return;
+
+ const MRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
// Now that we have a stack slot for each register to be saved, insert spill
// code into the entry block...
MachineBasicBlock *MBB = Fn.begin();
MachineBasicBlock::iterator I = MBB->begin();
for (unsigned i = 0, e = RegsToSave.size(); i != e; ++i) {
- const TargetRegisterClass *RC = RegInfo->getRegClass(RegsToSave[i]);
-
- // Insert the spill to the stack frame...
- RegInfo->storeRegToStackSlot(*MBB, I, RegsToSave[i], StackSlots[i], RC);
+ // Insert the spill to the stack frame.
+ RegInfo->storeRegToStackSlot(*MBB, I, RegsToSave[i], StackSlots[i]);
}
// Add code to restore the callee-save registers in each exiting block.
- const TargetInstrInfo &TII = Fn.getTarget().getInstrInfo();
+ const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
for (MachineFunction::iterator FI = Fn.begin(), E = Fn.end(); FI != E; ++FI) {
// If last instruction is a return instruction, add an epilogue
- if (TII.isReturn(FI->back()->getOpcode())) {
- MBB = FI; I = MBB->end()-1;
+ if (!FI->empty() && TII.isReturn(FI->back().getOpcode())) {
+ MBB = FI;
+ I = MBB->end(); --I;
for (unsigned i = 0, e = RegsToSave.size(); i != e; ++i) {
- const TargetRegisterClass *RC = RegInfo->getRegClass(RegsToSave[i]);
- RegInfo->loadRegFromStackSlot(*MBB, I, RegsToSave[i],StackSlots[i], RC);
- --I; // Insert in reverse order
+ RegInfo->loadRegFromStackSlot(*MBB, I, RegsToSave[i],StackSlots[i]);
+ --I; // Insert in reverse order
}
}
}
/// abstract stack objects...
///
void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
- const TargetFrameInfo &TFI = Fn.getTarget().getFrameInfo();
+ const TargetFrameInfo &TFI = *Fn.getTarget().getFrameInfo();
bool StackGrowsDown =
TFI.getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
- assert(StackGrowsDown && "Only tested on stack down growing targets!");
// Loop over all of the stack objects, assigning sequential addresses...
MachineFrameInfo *FFI = Fn.getFrameInfo();
unsigned StackAlignment = TFI.getStackAlignment();
- // Start at the beginning of the local area...
+ // Start at the beginning of the local area.
+ // The Offset is the distance from the stack top in the direction
+ // of stack growth -- so it's always positive.
int Offset = TFI.getOffsetOfLocalArea();
+ if (StackGrowsDown)
+ Offset = -Offset;
+ assert(Offset >= 0
+ && "Local area offset should be in direction of stack growth");
+
+ // If there are fixed sized objects that are preallocated in the local area,
+ // non-fixed objects can't be allocated right at the start of local area.
+ // We currently don't support filling in holes in between fixed sized objects,
+ // so we adjust 'Offset' to point to the end of last fixed sized
+ // preallocated object.
+ for (int i = FFI->getObjectIndexBegin(); i != 0; ++i) {
+ int FixedOff;
+ if (StackGrowsDown) {
+ // The maximum distance from the stack pointer is at lower address of
+ // the object -- which is given by offset. For down growing stack
+ // the offset is negative, so we negate the offset to get the distance.
+ FixedOff = -FFI->getObjectOffset(i);
+ } else {
+ // The maximum distance from the start pointer is at the upper
+ // address of the object.
+ FixedOff = FFI->getObjectOffset(i) + FFI->getObjectSize(i);
+ }
+ if (FixedOff > Offset) Offset = FixedOff;
+ }
+
for (unsigned i = 0, e = FFI->getObjectIndexEnd(); i != e; ++i) {
- Offset += FFI->getObjectSize(i); // Allocate Size bytes...
+ // If stack grows down, we need to add size of find the lowest
+ // address of the object.
+ if (StackGrowsDown)
+ Offset += FFI->getObjectSize(i);
unsigned Align = FFI->getObjectAlignment(i);
assert(Align <= StackAlignment && "Cannot align stack object to higher "
"alignment boundary than the stack itself!");
Offset = (Offset+Align-1)/Align*Align; // Adjust to Alignment boundary...
- FFI->setObjectOffset(i, -Offset); // Set the computed offset
+ if (StackGrowsDown) {
+ FFI->setObjectOffset(i, -Offset); // Set the computed offset
+ } else {
+ FFI->setObjectOffset(i, Offset);
+ Offset += FFI->getObjectSize(i);
+ }
}
- // Align the final stack pointer offset...
- Offset = (Offset+StackAlignment-1)/StackAlignment*StackAlignment;
+ // Align the final stack pointer offset, but only if there are calls in the
+ // function. This ensures that any calls to subroutines have their stack
+ // frames suitable aligned.
+ if (FFI->hasCalls())
+ Offset = (Offset+StackAlignment-1)/StackAlignment*StackAlignment;
// Set the final value of the stack pointer...
- FFI->setStackSize(Offset-TFI.getOffsetOfLocalArea());
+ FFI->setStackSize(Offset+TFI.getOffsetOfLocalArea());
}
Fn.getTarget().getRegisterInfo()->emitPrologue(Fn);
// Add epilogue to restore the callee-save registers in each exiting block
- const TargetInstrInfo &TII = Fn.getTarget().getInstrInfo();
+ const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
// If last instruction is a return instruction, add an epilogue
- if (!I->empty() && TII.isReturn(I->back()->getOpcode()))
+ if (!I->empty() && TII.isReturn(I->back().getOpcode()))
Fn.getTarget().getRegisterInfo()->emitEpilogue(Fn, *I);
}
}
for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I)
- for (unsigned i = 0, e = (*I)->getNumOperands(); i != e; ++i)
- if ((*I)->getOperand(i).isFrameIndex()) {
- // If this instruction has a FrameIndex operand, we need to use that
- // target machine register info object to eliminate it.
- MRI.eliminateFrameIndex(Fn, I);
- break;
- }
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
+ if (I->getOperand(i).isFrameIndex()) {
+ // If this instruction has a FrameIndex operand, we need to use that
+ // target machine register info object to eliminate it.
+ MRI.eliminateFrameIndex(I);
+ break;
+ }
}
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