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* Use the PHI Elimination pass 

llvm-svn: 5220
This commit is contained in:
Chris Lattner 2003-01-13 00:26:08 +00:00
parent bfa5319eb2
commit cbedb8b400
1 changed files with 6 additions and 80 deletions
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86
llvm/lib/CodeGen/RegAllocSimple.cpp
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@ -7,6 +7,7 @@
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/SSARegMap.h"
@ -46,14 +47,14 @@ namespace {
/// runOnMachineFunction - Register allocate the whole function
bool runOnMachineFunction(MachineFunction &Fn);
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequiredID(PHIEliminationID); // Eliminate PHI nodes
MachineFunctionPass::getAnalysisUsage(AU);
}
private:
/// AllocateBasicBlock - Register allocate the specified basic block.
void AllocateBasicBlock(MachineBasicBlock &MBB);
/// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions
/// in predecessor basic blocks.
void EliminatePHINodes(MachineBasicBlock &MBB);
/// getStackSpaceFor - This returns the offset of the specified virtual
/// register on the stack, allocating space if neccesary.
int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
@ -88,8 +89,7 @@ int RegAllocSimple::getStackSpaceFor(unsigned VirtReg,
return I->second; // Already has space allocated?
// Allocate a new stack object for this spill location...
int FrameIdx =
MF->getFrameInfo()->CreateStackObject(RC->getSize(), RC->getAlignment());
int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC);
// Assign the slot...
StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
@ -137,74 +137,6 @@ void RegAllocSimple::spillVirtReg(MachineBasicBlock &MBB,
}
/// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions in
/// predecessor basic blocks.
///
void RegAllocSimple::EliminatePHINodes(MachineBasicBlock &MBB) {
const MachineInstrInfo &MII = TM->getInstrInfo();
while (MBB.front()->getOpcode() == MachineInstrInfo::PHI) {
MachineInstr *MI = MBB.front();
// Unlink the PHI node from the basic block... but don't delete the PHI yet
MBB.erase(MBB.begin());
DEBUG(std::cerr << "num ops: " << MI->getNumOperands() << "\n");
assert(MI->getOperand(0).isVirtualRegister() &&
"PHI node doesn't write virt reg?");
unsigned virtualReg = MI->getOperand(0).getAllocatedRegNum();
for (int i = MI->getNumOperands() - 1; i >= 2; i-=2) {
MachineOperand &opVal = MI->getOperand(i-1);
// Get the MachineBasicBlock equivalent of the BasicBlock that is the
// source path the phi
MachineBasicBlock &opBlock = *MI->getOperand(i).getMachineBasicBlock();
// Check to make sure we haven't already emitted the copy for this block.
// This can happen because PHI nodes may have multiple entries for the
// same basic block. It doesn't matter which entry we use though, because
// all incoming values are guaranteed to be the same for a particular bb.
//
// Note that this is N^2 in the number of phi node entries, but since the
// # of entries is tiny, this is not a problem.
//
bool HaveNotEmitted = true;
for (int op = MI->getNumOperands() - 1; op != i; op -= 2)
if (&opBlock == MI->getOperand(op).getMachineBasicBlock()) {
HaveNotEmitted = false;
break;
}
if (HaveNotEmitted) {
MachineBasicBlock::iterator opI = opBlock.end();
MachineInstr *opMI = *--opI;
// must backtrack over ALL the branches in the previous block
while (MII.isBranch(opMI->getOpcode()) && opI != opBlock.begin())
opMI = *--opI;
// move back to the first branch instruction so new instructions
// are inserted right in front of it and not in front of a non-branch
//
if (!MII.isBranch(opMI->getOpcode()))
++opI;
const TargetRegisterClass *RC =
MF->getSSARegMap()->getRegClass(virtualReg);
assert(opVal.isVirtualRegister() &&
"Machine PHI Operands must all be virtual registers!");
RegInfo->copyRegToReg(opBlock, opI, virtualReg, opVal.getReg(), RC);
}
}
// really delete the PHI instruction now!
delete MI;
}
}
void RegAllocSimple::AllocateBasicBlock(MachineBasicBlock &MBB) {
// loop over each instruction
for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I) {
@ -281,12 +213,6 @@ bool RegAllocSimple::runOnMachineFunction(MachineFunction &Fn) {
TM = &MF->getTarget();
RegInfo = TM->getRegisterInfo();
// First pass: eliminate PHI instructions by inserting copies into predecessor
// blocks.
for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
MBB != MBBe; ++MBB)
EliminatePHINodes(*MBB);
// Loop over all of the basic blocks, eliminating virtual register references
for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
MBB != MBBe; ++MBB)