6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-14 11:32:34 +00:00
Code Issues Projects Releases Wiki Activity

Fix a problem that occurs when PHI nodes have multiple entries for the same predecessor

Browse Source 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@5055 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-12-15 20:48:03 +00:00
parent da7e453aac
commit 3f91ad7ba7
1 changed files with 45 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

73
lib/CodeGen/RegAllocSimple.cpp
View File

@ -283,43 +283,60 @@ void RegAllocSimple::EliminatePHINodes(MachineBasicBlock &MBB) {
const TargetRegisterClass* regClass = PhysRegClasses[physReg]; const TargetRegisterClass* regClass = PhysRegClasses[physReg];
assert(regClass && "Target register class not found!"); assert(regClass && "Target register class not found!");
unsigned dataSize = regClass->getDataSize(); unsigned dataSize = regClass->getDataSize();
for (int i = MI->getNumOperands() - 1; i >= 2; i-=2) { for (int i = MI->getNumOperands() - 1; i >= 2; i-=2) {
MachineOperand &opVal = MI->getOperand(i-1); MachineOperand &opVal = MI->getOperand(i-1);
// Get the MachineBasicBlock equivalent of the BasicBlock that is the // Get the MachineBasicBlock equivalent of the BasicBlock that is the
// source path the phi // source path the phi
MachineBasicBlock &opBlock = *MI->getOperand(i).getMachineBasicBlock(); MachineBasicBlock &opBlock = *MI->getOperand(i).getMachineBasicBlock();
MachineBasicBlock::iterator opI = opBlock.end();
MachineInstr *opMI = *--opI;
// must backtrack over ALL the branches in the previous block, until no // Check to make sure we haven't already emitted the copy for this block.
// more // This can happen because PHI nodes may have multiple entries for the
while (MII.isBranch(opMI->getOpcode()) && opI != opBlock.begin()) // same basic block. It doesn't matter which entry we use though, because
opMI = *--opI; // 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;
}
// move back to the first branch instruction so new instructions if (HaveNotEmitted) {
// are inserted right in front of it and not in front of a non-branch MachineBasicBlock::iterator opI = opBlock.end();
if (!MII.isBranch(opMI->getOpcode())) MachineInstr *opMI = *--opI;
++opI;
// must backtrack over ALL the branches in the previous block
// Retrieve the constant value from this op, move it to target while (MII.isBranch(opMI->getOpcode()) && opI != opBlock.begin())
// register of the phi opMI = *--opI;
if (opVal.isImmediate()) {
opI = RegInfo->moveImm2Reg(opBlock, opI, physReg, // move back to the first branch instruction so new instructions
(unsigned) opVal.getImmedValue(), // are inserted right in front of it and not in front of a non-branch
dataSize); if (!MII.isBranch(opMI->getOpcode()))
saveVirtRegToStack(opBlock, opI, virtualReg, physReg); ++opI;
} else {
// Allocate a physical register and add a move in the BB // Retrieve the constant value from this op, move it to target
unsigned opVirtualReg = (unsigned) opVal.getAllocatedRegNum(); // register of the phi
unsigned opPhysReg; if (opVal.isImmediate()) {
opI = moveUseToReg(opBlock, opI, opVirtualReg, physReg); opI = RegInfo->moveImm2Reg(opBlock, opI, physReg,
(unsigned) opVal.getImmedValue(),
// Save that register value to the stack of the TARGET REG dataSize);
saveVirtRegToStack(opBlock, opI, virtualReg, physReg); saveVirtRegToStack(opBlock, opI, virtualReg, physReg);
} else {
// Allocate a physical register and add a move in the BB
unsigned opVirtualReg = (unsigned) opVal.getAllocatedRegNum();
unsigned opPhysReg;
opI = moveUseToReg(opBlock, opI, opVirtualReg, physReg);
// Save that register value to the stack of the TARGET REG
saveVirtRegToStack(opBlock, opI, virtualReg, physReg);
}
} }
// make regs available to other instructions // make regs available to other instructions
clearAllRegs(); clearAllRegs();
} }