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028061d4eb
Moving MIRCanonicalizerPass vreg renaming code to MIRVRegNamerUtils so that it can be reused in another pass (ie planing to write a standalone mir-namer pass). I'm going to write a mir-namer pass so that next time someone has to author a test in MIR, they can use it to cleanup the naming and make it more readable by having the numbered vregs swapped out with named vregs. Differential Revision: https://reviews.llvm.org/D67114 llvm-svn: 370985
84 lines
3.5 KiB
C++
84 lines
3.5 KiB
C++
//===------------ MIRVRegNamerUtils.h - MIR VReg Renaming Utilities -------===//
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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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//
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// The purpose of these utilities is to abstract out parts of the MIRCanon pass
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// that are responsible for renaming virtual registers with the purpose of
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// sharing code with a MIRVRegNamer pass that could be the analog of the
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// opt -instnamer pass.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineInstrBuilder.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Support/raw_ostream.h"
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#include <queue>
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using namespace llvm;
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/// NamedVRegCursor - The cursor is an object that keeps track of what the next
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/// vreg name should be. It does book keeping to determine when to skip the
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/// index value and by how much, or if the next vreg name should be an increment
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/// from the previous.
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class NamedVRegCursor {
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MachineRegisterInfo &MRI;
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/// virtualVRegNumber - Book keeping of the last vreg position.
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unsigned virtualVRegNumber;
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/// SkipGapSize - Used to calculate a modulo amount to skip by after every
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/// sequence of instructions starting from a given side-effecting
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/// MachineInstruction for a given MachineBasicBlock. The general idea is that
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/// for a given program compiled with two different opt pipelines, there
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/// shouldn't be greater than SkipGapSize difference in how many vregs are in
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/// play between the two and for every def-use graph of vregs we rename we
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/// will round up to the next SkipGapSize'th number so that we have a high
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/// change of landing on the same name for two given matching side-effects
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/// for the two compilation outcomes.
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const unsigned SkipGapSize;
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/// RenamedInOtherBB - VRegs that we already renamed: ie breadcrumbs.
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std::vector<Register> RenamedInOtherBB;
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public:
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NamedVRegCursor() = delete;
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/// 1000 for the SkipGapSize was a good heuristic at the time of the writing
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/// of the MIRCanonicalizerPass. Adjust as needed.
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NamedVRegCursor(MachineRegisterInfo &MRI, unsigned SkipGapSize = 1000)
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: MRI(MRI), virtualVRegNumber(0), SkipGapSize(SkipGapSize) {}
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/// SkipGapSize - Skips modulo a gap value of indices. Indices are used to
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/// produce the next vreg name.
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void skipVRegs();
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unsigned getVirtualVReg() const { return virtualVRegNumber; }
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/// incrementVirtualVReg - This increments an index value that us used to
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/// create a new vreg name. This is not a Register.
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unsigned incrementVirtualVReg(unsigned incr = 1) {
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virtualVRegNumber += incr;
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return virtualVRegNumber;
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}
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/// createVirtualRegister - Given an existing vreg, create a named vreg to
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/// take its place.
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unsigned createVirtualRegister(unsigned VReg);
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/// renameVRegs - For a given MachineBasicBlock, scan for side-effecting
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/// instructions, walk the def-use from each side-effecting root (in sorted
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/// root order) and rename the encountered vregs in the def-use graph in a
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/// canonical ordering. This method maintains book keeping for which vregs
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/// were already renamed in RenamedInOtherBB.
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// @return changed
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bool renameVRegs(MachineBasicBlock *MBB);
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};
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