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* Fix a gross X86 hack that was intended to avoid allocating SP and BP

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* Implement register alias set support


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5082 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-12-16 17:44:42 +00:00
parent 69c198863d
commit c21be922bf
1 changed files with 38 additions and 5 deletions
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43
lib/CodeGen/RegAllocLocal.cpp
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@ -111,6 +111,22 @@ namespace {
/// in predecessor basic blocks.
void EliminatePHINodes(MachineBasicBlock &MBB);
/// isAllocatableRegister - A register may be used by the program if it's
/// not the stack or frame pointer.
bool isAllocatableRegister(unsigned R) const {
unsigned FP = RegInfo->getFramePointer(), SP = RegInfo->getStackPointer();
// Don't allocate the Frame or Stack pointers
if (R == FP || R == SP)
return false;
// Check to see if this register aliases the stack or frame pointer...
if (const unsigned *AliasSet = RegInfo->getAliasSet(R)) {
for (unsigned i = 0; AliasSet[i]; ++i)
if (AliasSet[i] == FP || AliasSet[i] == SP)
return false;
}
return true;
}
/// getStackSpaceFor - This returns the offset of the specified virtual
/// register on the stack, allocating space if neccesary.
@ -130,6 +146,16 @@ namespace {
void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
unsigned VirtReg, unsigned PhysReg);
/// spillPhysReg - This method spills the specified physical register into
/// the virtual register slot associated with it.
//
void spillPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
unsigned PhysReg) {
assert(PhysRegsUsed.find(PhysReg) != PhysRegsUsed.end() &&
"Physical register is not used: cannot spill it!");
spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
}
void AssignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
@ -219,9 +245,7 @@ unsigned RA::getFreeReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
It != E; ++It) {
unsigned R = *It;
if (PhysRegsUsed.find(R) == PhysRegsUsed.end()) // Is reg unused?
/// FIXME: Hack
if (R != RegInfo->getFramePointer() && R != RegInfo->getStackPointer() &&
R != 13 && R != 14) {
if (isAllocatableRegister(R)) {
// Found an unused register!
PhysReg = R;
break;
@ -231,6 +255,7 @@ unsigned RA::getFreeReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
// If we didn't find an unused register, scavange one now!
if (PhysReg == 0) {
unsigned i = 0;
assert(!PhysRegsUseOrder.empty() && "No allocated registers??");
while (PhysRegClasses[PhysRegsUseOrder[i]] != RegClass) {
++i;
assert(i != PhysRegsUseOrder.size() &&
@ -240,9 +265,17 @@ unsigned RA::getFreeReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
// At this point PhysRegsUseOrder[i] is the least recently used register of
// compatible register class. Spill it to memory and reap its remains.
PhysReg = PhysRegsUseOrder[i];
spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
spillPhysReg(MBB, I, PhysReg);
}
// If the selected register aliases any other registers, we must make sure to
// spill them as well...
if (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg))
for (unsigned i = 0; AliasSet[i]; ++i)
if (PhysRegsUsed.count(AliasSet[i])) // Spill aliased register...
spillPhysReg(MBB, I, AliasSet[i]);
// Now that we know which register we need to assign this to, do it now!
AssignVirtToPhysReg(VirtReg, PhysReg);
return PhysReg;
@ -417,7 +450,7 @@ void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
// Spill the incoming value, because we are about to change the
// register contents.
spillVirtReg(MBB, I, PhysRegsUsed[DestPhysReg], DestPhysReg);
spillPhysReg(MBB, I, DestPhysReg);
AssignVirtToPhysReg(DestVirtReg, DestPhysReg);
} else {
DestPhysReg = getFreeReg(MBB, I, DestVirtReg);