119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman//===-- SpillPlacement.cpp - Optimal Spill Code Placement -----------------===// 219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// 319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// The LLVM Compiler Infrastructure 419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// 519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// This file is distributed under the University of Illinois Open Source 619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// License. See LICENSE.TXT for details. 719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// 819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman//===----------------------------------------------------------------------===// 919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// 1019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// This file implements the spill code placement analysis. 1119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// 1219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// Each edge bundle corresponds to a node in a Hopfield network. Constraints on 1319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// basic blocks are weighted by the block frequency and added to become the node 1419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// bias. 1519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// 1619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// Transparent basic blocks have the variable live through, but don't care if it 1719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// is spilled or in a register. These blocks become connections in the Hopfield 1819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// network, again weighted by block frequency. 1919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// 2019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// The Hopfield network minimizes (possibly locally) its energy function: 2119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// 2219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// E = -sum_n V_n * ( B_n + sum_{n, m linked by b} V_m * F_b ) 2319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// 2419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// The energy function represents the expected spill code execution frequency, 2519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// or the cost of spilling. This is a Lyapunov function which never increases 2619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// when a node is updated. It is guaranteed to converge to a local minimum. 2719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman// 2819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman//===----------------------------------------------------------------------===// 2919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 3019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman#define DEBUG_TYPE "spillplacement" 3119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman#include "SpillPlacement.h" 3219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman#include "llvm/CodeGen/EdgeBundles.h" 3319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman#include "llvm/CodeGen/LiveIntervalAnalysis.h" 3419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman#include "llvm/CodeGen/MachineBasicBlock.h" 3519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman#include "llvm/CodeGen/MachineFunction.h" 3619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman#include "llvm/CodeGen/MachineLoopInfo.h" 3719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman#include "llvm/CodeGen/Passes.h" 3819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman#include "llvm/Support/Debug.h" 3919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman#include "llvm/Support/Format.h" 4019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 4119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanusing namespace llvm; 4219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 4319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanchar SpillPlacement::ID = 0; 4419bac1e08be200c31efd26f0f5fd144c9b3eefd3John BaumanINITIALIZE_PASS_BEGIN(SpillPlacement, "spill-code-placement", 4519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman "Spill Code Placement Analysis", true, true) 4619bac1e08be200c31efd26f0f5fd144c9b3eefd3John BaumanINITIALIZE_PASS_DEPENDENCY(EdgeBundles) 4719bac1e08be200c31efd26f0f5fd144c9b3eefd3John BaumanINITIALIZE_PASS_DEPENDENCY(MachineLoopInfo) 4819bac1e08be200c31efd26f0f5fd144c9b3eefd3John BaumanINITIALIZE_PASS_END(SpillPlacement, "spill-code-placement", 4919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman "Spill Code Placement Analysis", true, true) 5019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 5119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanchar &llvm::SpillPlacementID = SpillPlacement::ID; 5219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 5319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanvoid SpillPlacement::getAnalysisUsage(AnalysisUsage &AU) const { 5419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman AU.setPreservesAll(); 5519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman AU.addRequiredTransitive<EdgeBundles>(); 5619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman AU.addRequiredTransitive<MachineLoopInfo>(); 5719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman MachineFunctionPass::getAnalysisUsage(AU); 5819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman} 5919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 6019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// Node - Each edge bundle corresponds to a Hopfield node. 6119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// 6219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// The node contains precomputed frequency data that only depends on the CFG, 6319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// but Bias and Links are computed each time placeSpills is called. 6419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// 6519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// The node Value is positive when the variable should be in a register. The 6619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// value can change when linked nodes change, but convergence is very fast 6719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// because all weights are positive. 6819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// 6919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanstruct SpillPlacement::Node { 7019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// Scale - Inverse block frequency feeding into[0] or out of[1] the bundle. 7119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// Ideally, these two numbers should be identical, but inaccuracies in the 7219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// block frequency estimates means that we need to normalize ingoing and 7319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// outgoing frequencies separately so they are commensurate. 7419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman float Scale[2]; 7519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 7619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// Bias - Normalized contributions from non-transparent blocks. 7719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// A bundle connected to a MustSpill block has a huge negative bias, 7819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// otherwise it is a number in the range [-2;2]. 7919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman float Bias; 8019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 8119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// Value - Output value of this node computed from the Bias and links. 8219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// This is always in the range [-1;1]. A positive number means the variable 8319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// should go in a register through this bundle. 8419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman float Value; 8519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 8619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman typedef SmallVector<std::pair<float, unsigned>, 4> LinkVector; 8719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 8819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// Links - (Weight, BundleNo) for all transparent blocks connecting to other 8919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// bundles. The weights are all positive and add up to at most 2, weights 9019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// from ingoing and outgoing nodes separately add up to a most 1. The weight 9119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// sum can be less than 2 when the variable is not live into / out of some 9219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// connected basic blocks. 9319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman LinkVector Links; 9419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 9519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// preferReg - Return true when this node prefers to be in a register. 9619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman bool preferReg() const { 9719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Undecided nodes (Value==0) go on the stack. 9819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman return Value > 0; 9919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 10019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 10119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// mustSpill - Return True if this node is so biased that it must spill. 10219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman bool mustSpill() const { 10319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Actually, we must spill if Bias < sum(weights). 10419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // It may be worth it to compute the weight sum here? 10519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman return Bias < -2.0f; 10619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 10719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 10819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// Node - Create a blank Node. 10919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Node() { 11019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Scale[0] = Scale[1] = 0; 11119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 11219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 11319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// clear - Reset per-query data, but preserve frequencies that only depend on 11419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // the CFG. 11519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman void clear() { 11619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Bias = Value = 0; 11719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Links.clear(); 11819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 11919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 12019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// addLink - Add a link to bundle b with weight w. 12119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// out=0 for an ingoing link, and 1 for an outgoing link. 12219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman void addLink(unsigned b, float w, bool out) { 12319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Normalize w relative to all connected blocks from that direction. 12419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman w *= Scale[out]; 12519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 12619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // There can be multiple links to the same bundle, add them up. 12719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (LinkVector::iterator I = Links.begin(), E = Links.end(); I != E; ++I) 12819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (I->second == b) { 12919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman I->first += w; 13019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman return; 13119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 13219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // This must be the first link to b. 13319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Links.push_back(std::make_pair(w, b)); 13419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 13519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 13619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// addBias - Bias this node from an ingoing[0] or outgoing[1] link. 13719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// Return the change to the total number of positive biases. 13819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman void addBias(float w, bool out) { 13919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Normalize w relative to all connected blocks from that direction. 14019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman w *= Scale[out]; 14119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Bias += w; 14219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 14319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 14419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// update - Recompute Value from Bias and Links. Return true when node 14519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman /// preference changes. 14619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman bool update(const Node nodes[]) { 14719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Compute the weighted sum of inputs. 14819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman float Sum = Bias; 14919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (LinkVector::iterator I = Links.begin(), E = Links.end(); I != E; ++I) 15019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Sum += I->first * nodes[I->second].Value; 15119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 15219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // The weighted sum is going to be in the range [-2;2]. Ideally, we should 15319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // simply set Value = sign(Sum), but we will add a dead zone around 0 for 15419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // two reasons: 15519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // 1. It avoids arbitrary bias when all links are 0 as is possible during 15619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // initial iterations. 15719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // 2. It helps tame rounding errors when the links nominally sum to 0. 15819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman const float Thres = 1e-4f; 15919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman bool Before = preferReg(); 16019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (Sum < -Thres) 16119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Value = -1; 16219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman else if (Sum > Thres) 16319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Value = 1; 16419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman else 16519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Value = 0; 16619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman return Before != preferReg(); 16719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 16819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman}; 16919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 17019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanbool SpillPlacement::runOnMachineFunction(MachineFunction &mf) { 17119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman MF = &mf; 17219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman bundles = &getAnalysis<EdgeBundles>(); 17319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman loops = &getAnalysis<MachineLoopInfo>(); 17419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 17519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman assert(!nodes && "Leaking node array"); 17619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes = new Node[bundles->getNumBundles()]; 17719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 17819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Compute total ingoing and outgoing block frequencies for all bundles. 17919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman BlockFrequency.resize(mf.getNumBlockIDs()); 18019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (MachineFunction::iterator I = mf.begin(), E = mf.end(); I != E; ++I) { 18119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman float Freq = LiveIntervals::getSpillWeight(true, false, 18219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman loops->getLoopDepth(I)); 18319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman unsigned Num = I->getNumber(); 18419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman BlockFrequency[Num] = Freq; 18519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[bundles->getBundle(Num, 1)].Scale[0] += Freq; 18619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[bundles->getBundle(Num, 0)].Scale[1] += Freq; 18719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 18819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 18919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Scales are reciprocal frequencies. 19019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (unsigned i = 0, e = bundles->getNumBundles(); i != e; ++i) 19119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (unsigned d = 0; d != 2; ++d) 19219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (nodes[i].Scale[d] > 0) 19319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[i].Scale[d] = 1 / nodes[i].Scale[d]; 19419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 19519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // We never change the function. 19619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman return false; 19719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman} 19819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 19919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanvoid SpillPlacement::releaseMemory() { 20019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman delete[] nodes; 20119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes = 0; 20219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman} 20319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 20419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// activate - mark node n as active if it wasn't already. 20519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanvoid SpillPlacement::activate(unsigned n) { 20619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (ActiveNodes->test(n)) 20719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman return; 20819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman ActiveNodes->set(n); 20919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[n].clear(); 21019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman} 21119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 21219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 21319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// addConstraints - Compute node biases and weights from a set of constraints. 21419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// Set a bit in NodeMask for each active node. 21519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanvoid SpillPlacement::addConstraints(ArrayRef<BlockConstraint> LiveBlocks) { 21619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (ArrayRef<BlockConstraint>::iterator I = LiveBlocks.begin(), 21719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman E = LiveBlocks.end(); I != E; ++I) { 21819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman float Freq = getBlockFrequency(I->Number); 21919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman const float Bias[] = { 22019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 0, // DontCare, 22119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 1, // PrefReg, 22219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman -1, // PrefSpill 22319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 0, // PrefBoth 22419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman -HUGE_VALF // MustSpill 22519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman }; 22619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 22719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Live-in to block? 22819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (I->Entry != DontCare) { 22919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman unsigned ib = bundles->getBundle(I->Number, 0); 23019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman activate(ib); 23119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[ib].addBias(Freq * Bias[I->Entry], 1); 23219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 23319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 23419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Live-out from block? 23519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (I->Exit != DontCare) { 23619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman unsigned ob = bundles->getBundle(I->Number, 1); 23719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman activate(ob); 23819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[ob].addBias(Freq * Bias[I->Exit], 0); 23919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 24019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 24119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman} 24219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 24319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// addPrefSpill - Same as addConstraints(PrefSpill) 24419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanvoid SpillPlacement::addPrefSpill(ArrayRef<unsigned> Blocks, bool Strong) { 24519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (ArrayRef<unsigned>::iterator I = Blocks.begin(), E = Blocks.end(); 24619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman I != E; ++I) { 24719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman float Freq = getBlockFrequency(*I); 24819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (Strong) 24919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Freq += Freq; 25019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman unsigned ib = bundles->getBundle(*I, 0); 25119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman unsigned ob = bundles->getBundle(*I, 1); 25219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman activate(ib); 25319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman activate(ob); 25419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[ib].addBias(-Freq, 1); 25519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[ob].addBias(-Freq, 0); 25619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 25719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman} 25819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 25919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanvoid SpillPlacement::addLinks(ArrayRef<unsigned> Links) { 26019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (ArrayRef<unsigned>::iterator I = Links.begin(), E = Links.end(); I != E; 26119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman ++I) { 26219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman unsigned Number = *I; 26319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman unsigned ib = bundles->getBundle(Number, 0); 26419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman unsigned ob = bundles->getBundle(Number, 1); 26519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 26619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Ignore self-loops. 26719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (ib == ob) 26819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman continue; 26919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman activate(ib); 27019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman activate(ob); 27119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (nodes[ib].Links.empty() && !nodes[ib].mustSpill()) 27219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Linked.push_back(ib); 27319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (nodes[ob].Links.empty() && !nodes[ob].mustSpill()) 27419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Linked.push_back(ob); 27519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman float Freq = getBlockFrequency(Number); 27619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[ib].addLink(ob, Freq, 1); 27719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[ob].addLink(ib, Freq, 0); 27819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 27919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman} 28019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 28119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanbool SpillPlacement::scanActiveBundles() { 28219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Linked.clear(); 28319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman RecentPositive.clear(); 28419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (int n = ActiveNodes->find_first(); n>=0; n = ActiveNodes->find_next(n)) { 28519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[n].update(nodes); 28619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // A node that must spill, or a node without any links is not going to 28719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // change its value ever again, so exclude it from iterations. 28819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (nodes[n].mustSpill()) 28919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman continue; 29019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (!nodes[n].Links.empty()) 29119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Linked.push_back(n); 29219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (nodes[n].preferReg()) 29319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman RecentPositive.push_back(n); 29419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 29519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman return !RecentPositive.empty(); 29619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman} 29719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 29819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// iterate - Repeatedly update the Hopfield nodes until stability or the 29919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// maximum number of iterations is reached. 30019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman/// @param Linked - Numbers of linked nodes that need updating. 30119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanvoid SpillPlacement::iterate() { 30219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // First update the recently positive nodes. They have likely received new 30319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // negative bias that will turn them off. 30419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman while (!RecentPositive.empty()) 30519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman nodes[RecentPositive.pop_back_val()].update(nodes); 30619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 30719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (Linked.empty()) 30819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman return; 30919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 31019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Run up to 10 iterations. The edge bundle numbering is closely related to 31119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // basic block numbering, so there is a strong tendency towards chains of 31219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // linked nodes with sequential numbers. By scanning the linked nodes 31319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // backwards and forwards, we make it very likely that a single node can 31419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // affect the entire network in a single iteration. That means very fast 31519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // convergence, usually in a single iteration. 31619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (unsigned iteration = 0; iteration != 10; ++iteration) { 31719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Scan backwards, skipping the last node which was just updated. 31819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman bool Changed = false; 31919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (SmallVectorImpl<unsigned>::const_reverse_iterator I = 32019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman llvm::next(Linked.rbegin()), E = Linked.rend(); I != E; ++I) { 32119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman unsigned n = *I; 32219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (nodes[n].update(nodes)) { 32319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Changed = true; 32419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (nodes[n].preferReg()) 32519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman RecentPositive.push_back(n); 32619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 32719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 32819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (!Changed || !RecentPositive.empty()) 32919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman return; 33019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 33119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Scan forwards, skipping the first node which was just updated. 33219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Changed = false; 33319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (SmallVectorImpl<unsigned>::const_iterator I = 33419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman llvm::next(Linked.begin()), E = Linked.end(); I != E; ++I) { 33519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman unsigned n = *I; 33619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (nodes[n].update(nodes)) { 33719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Changed = true; 33819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (nodes[n].preferReg()) 33919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman RecentPositive.push_back(n); 34019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 34119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 34219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (!Changed || !RecentPositive.empty()) 34319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman return; 34419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 34519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman} 34619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 34719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanvoid SpillPlacement::prepare(BitVector &RegBundles) { 34819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Linked.clear(); 34919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman RecentPositive.clear(); 35019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Reuse RegBundles as our ActiveNodes vector. 35119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman ActiveNodes = &RegBundles; 35219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman ActiveNodes->clear(); 35319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman ActiveNodes->resize(bundles->getNumBundles()); 35419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman} 35519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 35619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Baumanbool 35719bac1e08be200c31efd26f0f5fd144c9b3eefd3John BaumanSpillPlacement::finish() { 35819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman assert(ActiveNodes && "Call prepare() first"); 35919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman 36019bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman // Write preferences back to ActiveNodes. 36119bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman bool Perfect = true; 36219bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman for (int n = ActiveNodes->find_first(); n>=0; n = ActiveNodes->find_next(n)) 36319bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman if (!nodes[n].preferReg()) { 36419bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman ActiveNodes->reset(n); 36519bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman Perfect = false; 36619bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman } 36719bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman ActiveNodes = 0; 36819bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman return Perfect; 36919bac1e08be200c31efd26f0f5fd144c9b3eefd3John Bauman} 370