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//===-- PrologEpilogCodeInserter.cpp - Insert Prolog & Epilog code for fn -===//
//
// Insert SAVE/RESTORE instructions for the function
//
// Insert prolog code at the unique function entry point.
// Insert epilog code at each function exit point.
// InsertPrologEpilog invokes these only if the function is not compiled
// with the leaf function optimization.
//
//===----------------------------------------------------------------------===//
#include "SparcInternals.h"
#include "SparcRegClassInfo.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineFunctionInfo.h"
#include "llvm/CodeGen/MachineCodeForInstruction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/Pass.h"
#include "llvm/Function.h"
namespace {
struct InsertPrologEpilogCode : public MachineFunctionPass {
const char *getPassName() const { return "Sparc Prolog/Epilog Inserter"; }
bool runOnMachineFunction(MachineFunction &F) {
if (!F.getInfo()->isCompiledAsLeafMethod()) {
InsertPrologCode(F);
InsertEpilogCode(F);
}
return false;
}
void InsertPrologCode(MachineFunction &F);
void InsertEpilogCode(MachineFunction &F);
};
} // End anonymous namespace
//------------------------------------------------------------------------
// Create prolog and epilog code for procedure entry and exit
//------------------------------------------------------------------------
void InsertPrologEpilogCode::InsertPrologCode(MachineFunction &MF)
{
std::vector<MachineInstr*> mvec;
const TargetMachine &TM = MF.getTarget();
const TargetFrameInfo& frameInfo = TM.getFrameInfo();
// The second operand is the stack size. If it does not fit in the
// immediate field, we have to use a free register to hold the size.
// See the comments below for the choice of this register.
//
unsigned staticStackSize = MF.getInfo()->getStaticStackSize();
if (staticStackSize < (unsigned) frameInfo.getMinStackFrameSize())
staticStackSize = (unsigned) frameInfo.getMinStackFrameSize();
if (unsigned padsz = (staticStackSize %
(unsigned) frameInfo.getStackFrameSizeAlignment()))
staticStackSize += frameInfo.getStackFrameSizeAlignment() - padsz;
int32_t C = - (int) staticStackSize;
int SP = TM.getRegInfo().getStackPointer();
if (TM.getInstrInfo().constantFitsInImmedField(SAVE, staticStackSize)) {
mvec.push_back(BuildMI(SAVE, 3).addMReg(SP).addSImm(C).addMReg(SP,
MOTy::Def));
} else {
// We have to put the stack size value into a register before SAVE.
// Use register %g1 since it is volatile across calls. Note that the
// local (%l) and in (%i) registers cannot be used before the SAVE!
// Do this by creating a code sequence equivalent to:
// SETSW -(stackSize), %g1
int uregNum = TM.getRegInfo().getUnifiedRegNum(
TM.getRegInfo().getRegClassIDOfType(Type::IntTy),
SparcIntRegClass::g1);
MachineInstr* M = BuildMI(SETHI, 2).addSImm(C).addMReg(uregNum, MOTy::Def);
M->setOperandHi32(0);
mvec.push_back(M);
M = BuildMI(OR, 3).addMReg(uregNum).addSImm(C).addMReg(uregNum, MOTy::Def);
M->setOperandLo32(1);
mvec.push_back(M);
M = BuildMI(SRA, 3).addMReg(uregNum).addZImm(0).addMReg(uregNum, MOTy::Def);
mvec.push_back(M);
// Now generate the SAVE using the value in register %g1
M = BuildMI(SAVE, 3).addMReg(SP).addMReg(uregNum).addMReg(SP, MOTy::Def);
mvec.push_back(M);
}
MF.front().insert(MF.front().begin(), mvec.begin(), mvec.end());
}
void InsertPrologEpilogCode::InsertEpilogCode(MachineFunction &MF)
{
const TargetMachine &TM = MF.getTarget();
const TargetInstrInfo &MII = TM.getInstrInfo();
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
MachineBasicBlock &MBB = *I;
BasicBlock &BB = *I->getBasicBlock();
Instruction *TermInst = (Instruction*)BB.getTerminator();
if (TermInst->getOpcode() == Instruction::Ret)
{
int ZR = TM.getRegInfo().getZeroRegNum();
MachineInstr *Restore =
BuildMI(RESTORE, 3).addMReg(ZR).addSImm(0).addMReg(ZR, MOTy::Def);
MachineCodeForInstruction &termMvec =
MachineCodeForInstruction::get(TermInst);
// Remove the NOPs in the delay slots of the return instruction
unsigned numNOPs = 0;
while (termMvec.back()->getOpCode() == NOP)
{
assert( termMvec.back() == MBB.back());
delete MBB.pop_back();
termMvec.pop_back();
++numNOPs;
}
assert(termMvec.back() == MBB.back());
// Check that we found the right number of NOPs and have the right
// number of instructions to replace them.
unsigned ndelays = MII.getNumDelaySlots(termMvec.back()->getOpCode());
assert(numNOPs == ndelays && "Missing NOPs in delay slots?");
assert(ndelays == 1 && "Cannot use epilog code for delay slots?");
// Append the epilog code to the end of the basic block.
MBB.push_back(Restore);
}
}
}
Pass* UltraSparc::getPrologEpilogInsertionPass() {
return new InsertPrologEpilogCode();
}
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