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Split saveCallerSavedRegisters into two methods for clarity, and add comments.

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Add support for targets that must spill certain physregs at certain locations.

Patch contributed by Nate Begeman, slightly hacked by me.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@15701 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2004-08-12 19:01:14 +00:00
parent 28690ea285
commit c330b68fb7
1 changed files with 52 additions and 9 deletions
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61
lib/CodeGen/PrologEpilogInserter.cpp
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@ -40,6 +40,9 @@ namespace {
// 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
@ -49,17 +52,28 @@ namespace {
// 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);
@ -74,15 +88,14 @@ namespace {
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();
@ -131,7 +144,6 @@ void PEI::saveCallerSavedRegisters(MachineFunction &Fn) {
// 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]) {
@ -150,13 +162,44 @@ void PEI::saveCallerSavedRegisters(MachineFunction &Fn) {
if (RegsToSave.empty())
return; // Early exit if no caller saved registers are modified!
unsigned NumFixedSpillSlots;
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];
int FrameIdx;
const TargetRegisterClass *RC = RegInfo->getRegClass(Reg);
// Check to see if this physreg must be spilled to a particular stack slot
// on this target.
std::pair<unsigned,int> *FixedSlot = FixedSpillSlots;
while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots &&
FixedSlot->first != Reg)
++FixedSlot;
if (FixedSlot == FixedSpillSlots+NumFixedSpillSlots) {
// Nope, just spill it anywhere convenient.
FrameIdx = FFI->CreateStackObject(RC);
} else {
// Spill it to the stack where we must.
FrameIdx = FFI->CreateFixedObject(RC->getSize(), 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...