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llvm-mirror/lib/CodeGen/PHIEliminationUtils.cpp
Chandler Carruth a490793037 Use the new script to sort the includes of every file under lib.
Sooooo many of these had incorrect or strange main module includes.
I have manually inspected all of these, and fixed the main module
include to be the nearest plausible thing I could find. If you own or
care about any of these source files, I encourage you to take some time
and check that these edits were sensible. I can't have broken anything
(I strictly added headers, and reordered them, never removed), but they
may not be the headers you'd really like to identify as containing the
API being implemented.

Many forward declarations and missing includes were added to a header
files to allow them to parse cleanly when included first. The main
module rule does in fact have its merits. =]

llvm-svn: 169131
2012-12-03 16:50:05 +00:00

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/ADT/SmallPtrSet.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineRegisterInfo.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);
}