mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2025-10-30 16:17:05 +00:00
a474685d06
function so that it can be shared with StrongPHIElimination. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120951 91177308-0d34-0410-b5e6-96231b3b80d8
62 lines
2.3 KiB
C++
62 lines
2.3 KiB
C++
//===-- PHIEliminationUtils.cpp - Helper functions for PHI elimination ----===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "PHIEliminationUtils.h"
|
|
#include "llvm/CodeGen/MachineBasicBlock.h"
|
|
#include "llvm/CodeGen/MachineFunction.h"
|
|
#include "llvm/CodeGen/MachineRegisterInfo.h"
|
|
#include "llvm/ADT/SmallPtrSet.h"
|
|
using namespace llvm;
|
|
|
|
// findCopyInsertPoint - Find a safe place in MBB to insert a copy from SrcReg
|
|
// when following the CFG edge to SuccMBB. This needs to be after any def of
|
|
// SrcReg, but before any subsequent point where control flow might jump out of
|
|
// the basic block.
|
|
MachineBasicBlock::iterator
|
|
llvm::findPHICopyInsertPoint(MachineBasicBlock* MBB, MachineBasicBlock* SuccMBB,
|
|
unsigned SrcReg) {
|
|
// Handle the trivial case trivially.
|
|
if (MBB->empty())
|
|
return MBB->begin();
|
|
|
|
// Usually, we just want to insert the copy before the first terminator
|
|
// instruction. However, for the edge going to a landing pad, we must insert
|
|
// the copy before the call/invoke instruction.
|
|
if (!SuccMBB->isLandingPad())
|
|
return MBB->getFirstTerminator();
|
|
|
|
// Discover any defs/uses in this basic block.
|
|
SmallPtrSet<MachineInstr*, 8> DefUsesInMBB;
|
|
MachineRegisterInfo& MRI = MBB->getParent()->getRegInfo();
|
|
for (MachineRegisterInfo::reg_iterator RI = MRI.reg_begin(SrcReg),
|
|
RE = MRI.reg_end(); RI != RE; ++RI) {
|
|
MachineInstr* DefUseMI = &*RI;
|
|
if (DefUseMI->getParent() == MBB)
|
|
DefUsesInMBB.insert(DefUseMI);
|
|
}
|
|
|
|
MachineBasicBlock::iterator InsertPoint;
|
|
if (DefUsesInMBB.empty()) {
|
|
// No defs. Insert the copy at the start of the basic block.
|
|
InsertPoint = MBB->begin();
|
|
} else if (DefUsesInMBB.size() == 1) {
|
|
// Insert the copy immediately after the def/use.
|
|
InsertPoint = *DefUsesInMBB.begin();
|
|
++InsertPoint;
|
|
} else {
|
|
// Insert the copy immediately after the last def/use.
|
|
InsertPoint = MBB->end();
|
|
while (!DefUsesInMBB.count(&*--InsertPoint)) {}
|
|
++InsertPoint;
|
|
}
|
|
|
|
// Make sure the copy goes after any phi nodes however.
|
|
return MBB->SkipPHIsAndLabels(InsertPoint);
|
|
}
|