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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
60 lines
2.2 KiB
C++
60 lines
2.2 KiB
C++
//===-- PHIEliminationUtils.cpp - Helper functions for PHI elimination ----===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "PHIEliminationUtils.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/CodeGen/MachineBasicBlock.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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using namespace llvm;
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// findCopyInsertPoint - Find a safe place in MBB to insert a copy from SrcReg
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// when following the CFG edge to SuccMBB. This needs to be after any def of
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// SrcReg, but before any subsequent point where control flow might jump out of
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// the basic block.
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MachineBasicBlock::iterator
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llvm::findPHICopyInsertPoint(MachineBasicBlock* MBB, MachineBasicBlock* SuccMBB,
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unsigned SrcReg) {
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// Handle the trivial case trivially.
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if (MBB->empty())
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return MBB->begin();
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// Usually, we just want to insert the copy before the first terminator
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// instruction. However, for the edge going to a landing pad, we must insert
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// the copy before the call/invoke instruction.
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if (!SuccMBB->isEHPad())
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return MBB->getFirstTerminator();
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// Discover any defs/uses in this basic block.
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SmallPtrSet<MachineInstr*, 8> DefUsesInMBB;
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MachineRegisterInfo& MRI = MBB->getParent()->getRegInfo();
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for (MachineInstr &RI : MRI.reg_instructions(SrcReg)) {
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if (RI.getParent() == MBB)
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DefUsesInMBB.insert(&RI);
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}
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MachineBasicBlock::iterator InsertPoint;
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if (DefUsesInMBB.empty()) {
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// No defs. Insert the copy at the start of the basic block.
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InsertPoint = MBB->begin();
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} else if (DefUsesInMBB.size() == 1) {
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// Insert the copy immediately after the def/use.
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InsertPoint = *DefUsesInMBB.begin();
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++InsertPoint;
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} else {
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// Insert the copy immediately after the last def/use.
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InsertPoint = MBB->end();
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while (!DefUsesInMBB.count(&*--InsertPoint)) {}
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++InsertPoint;
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}
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// Make sure the copy goes after any phi nodes but before
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// any debug nodes.
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return MBB->SkipPHIsAndLabels(InsertPoint);
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}
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