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Diffstat (limited to 'lib/CodeGen/ShrinkWrapping.cpp')
| -rw-r--r-- | lib/CodeGen/ShrinkWrapping.cpp | 1152 |
1 files changed, 0 insertions, 1152 deletions
diff --git a/lib/CodeGen/ShrinkWrapping.cpp b/lib/CodeGen/ShrinkWrapping.cpp deleted file mode 100644 index 6c826de..0000000 --- a/lib/CodeGen/ShrinkWrapping.cpp +++ /dev/null @@ -1,1152 +0,0 @@ -//===-- ShrinkWrapping.cpp - Reduce spills/restores of callee-saved regs --===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// This file implements a shrink wrapping variant of prolog/epilog insertion: -// - Spills and restores of callee-saved registers (CSRs) are placed in the -// machine CFG to tightly surround their uses so that execution paths that -// do not use CSRs do not pay the spill/restore penalty. -// -// - Avoiding placment of spills/restores in loops: if a CSR is used inside a -// loop the spills are placed in the loop preheader, and restores are -// placed in the loop exit nodes (the successors of loop _exiting_ nodes). -// -// - Covering paths without CSR uses: -// If a region in a CFG uses CSRs and has multiple entry and/or exit points, -// the use info for the CSRs inside the region is propagated outward in the -// CFG to ensure validity of the spill/restore placements. This decreases -// the effectiveness of shrink wrapping but does not require edge splitting -// in the machine CFG. -// -// This shrink wrapping implementation uses an iterative analysis to determine -// which basic blocks require spills and restores for CSRs. -// -// This pass uses MachineDominators and MachineLoopInfo. Loop information -// is used to prevent placement of callee-saved register spills/restores -// in the bodies of loops. -// -//===----------------------------------------------------------------------===// - -#define DEBUG_TYPE "shrink-wrap" - -#include "PrologEpilogInserter.h" -#include "llvm/ADT/DenseMap.h" -#include "llvm/ADT/PostOrderIterator.h" -#include "llvm/ADT/STLExtras.h" -#include "llvm/ADT/SparseBitVector.h" -#include "llvm/ADT/Statistic.h" -#include "llvm/CodeGen/MachineDominators.h" -#include "llvm/CodeGen/MachineFrameInfo.h" -#include "llvm/CodeGen/MachineInstr.h" -#include "llvm/CodeGen/MachineLoopInfo.h" -#include "llvm/CodeGen/MachineRegisterInfo.h" -#include "llvm/Support/CommandLine.h" -#include "llvm/Support/Compiler.h" -#include "llvm/Support/Debug.h" -#include "llvm/Target/TargetMachine.h" -#include "llvm/Target/TargetRegisterInfo.h" -#include <sstream> - -using namespace llvm; - -STATISTIC(numSRReduced, "Number of CSR spills+restores reduced."); - -// Shrink Wrapping: -static cl::opt<bool> -ShrinkWrapping("shrink-wrap", - cl::desc("Shrink wrap callee-saved register spills/restores")); - -// Shrink wrap only the specified function, a debugging aid. -static cl::opt<std::string> -ShrinkWrapFunc("shrink-wrap-func", cl::Hidden, - cl::desc("Shrink wrap the specified function"), - cl::value_desc("funcname"), - cl::init("")); - -// Debugging level for shrink wrapping. -enum ShrinkWrapDebugLevel { - Disabled, BasicInfo, Iterations, Details -}; - -static cl::opt<enum ShrinkWrapDebugLevel> -ShrinkWrapDebugging("shrink-wrap-dbg", cl::Hidden, - cl::desc("Print shrink wrapping debugging information"), - cl::values( - clEnumVal(Disabled , "disable debug output"), - clEnumVal(BasicInfo , "print basic DF sets"), - clEnumVal(Iterations, "print SR sets for each iteration"), - clEnumVal(Details , "print all DF sets"), - clEnumValEnd)); - - -void PEI::getAnalysisUsage(AnalysisUsage &AU) const { - AU.setPreservesCFG(); - if (ShrinkWrapping || ShrinkWrapFunc != "") { - AU.addRequired<MachineLoopInfo>(); - AU.addRequired<MachineDominatorTree>(); - } - AU.addPreserved<MachineLoopInfo>(); - AU.addPreserved<MachineDominatorTree>(); - AU.addRequired<TargetPassConfig>(); - MachineFunctionPass::getAnalysisUsage(AU); -} - -//===----------------------------------------------------------------------===// -// ShrinkWrapping implementation -//===----------------------------------------------------------------------===// - -// Convienences for dealing with machine loops. -MachineBasicBlock* PEI::getTopLevelLoopPreheader(MachineLoop* LP) { - assert(LP && "Machine loop is NULL."); - MachineBasicBlock* PHDR = LP->getLoopPreheader(); - MachineLoop* PLP = LP->getParentLoop(); - while (PLP) { - PHDR = PLP->getLoopPreheader(); - PLP = PLP->getParentLoop(); - } - return PHDR; -} - -MachineLoop* PEI::getTopLevelLoopParent(MachineLoop *LP) { - if (LP == 0) - return 0; - MachineLoop* PLP = LP->getParentLoop(); - while (PLP) { - LP = PLP; - PLP = PLP->getParentLoop(); - } - return LP; -} - -bool PEI::isReturnBlock(MachineBasicBlock* MBB) { - return (MBB && !MBB->empty() && MBB->back().isReturn()); -} - -// Initialize shrink wrapping DFA sets, called before iterations. -void PEI::clearAnticAvailSets() { - AnticIn.clear(); - AnticOut.clear(); - AvailIn.clear(); - AvailOut.clear(); -} - -// Clear all sets constructed by shrink wrapping. -void PEI::clearAllSets() { - ReturnBlocks.clear(); - clearAnticAvailSets(); - UsedCSRegs.clear(); - CSRUsed.clear(); - TLLoops.clear(); - CSRSave.clear(); - CSRRestore.clear(); -} - -// Initialize all shrink wrapping data. -void PEI::initShrinkWrappingInfo() { - clearAllSets(); - EntryBlock = 0; -#ifndef NDEBUG - HasFastExitPath = false; -#endif - ShrinkWrapThisFunction = ShrinkWrapping; - // DEBUG: enable or disable shrink wrapping for the current function - // via --shrink-wrap-func=<funcname>. -#ifndef NDEBUG - if (ShrinkWrapFunc != "") { - std::string MFName = MF->getName().str(); - ShrinkWrapThisFunction = (MFName == ShrinkWrapFunc); - } -#endif -} - - -/// placeCSRSpillsAndRestores - determine which MBBs of the function -/// need save, restore code for callee-saved registers by doing a DF analysis -/// similar to the one used in code motion (GVNPRE). This produces maps of MBBs -/// to sets of registers (CSRs) for saves and restores. MachineLoopInfo -/// is used to ensure that CSR save/restore code is not placed inside loops. -/// This function computes the maps of MBBs -> CSRs to spill and restore -/// in CSRSave, CSRRestore. -/// -/// If shrink wrapping is not being performed, place all spills in -/// the entry block, all restores in return blocks. In this case, -/// CSRSave has a single mapping, CSRRestore has mappings for each -/// return block. -/// -void PEI::placeCSRSpillsAndRestores(MachineFunction &Fn) { - - DEBUG(MF = &Fn); - - initShrinkWrappingInfo(); - - DEBUG(if (ShrinkWrapThisFunction) { - dbgs() << "Place CSR spills/restores for " - << MF->getName() << "\n"; - }); - - if (calculateSets(Fn)) - placeSpillsAndRestores(Fn); -} - -/// calcAnticInOut - calculate the anticipated in/out reg sets -/// for the given MBB by looking forward in the MCFG at MBB's -/// successors. -/// -bool PEI::calcAnticInOut(MachineBasicBlock* MBB) { - bool changed = false; - - // AnticOut[MBB] = INTERSECT(AnticIn[S] for S in SUCCESSORS(MBB)) - SmallVector<MachineBasicBlock*, 4> successors; - for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(), - SE = MBB->succ_end(); SI != SE; ++SI) { - MachineBasicBlock* SUCC = *SI; - if (SUCC != MBB) - successors.push_back(SUCC); - } - - unsigned i = 0, e = successors.size(); - if (i != e) { - CSRegSet prevAnticOut = AnticOut[MBB]; - MachineBasicBlock* SUCC = successors[i]; - - AnticOut[MBB] = AnticIn[SUCC]; - for (++i; i != e; ++i) { - SUCC = successors[i]; - AnticOut[MBB] &= AnticIn[SUCC]; - } - if (prevAnticOut != AnticOut[MBB]) - changed = true; - } - - // AnticIn[MBB] = UNION(CSRUsed[MBB], AnticOut[MBB]); - CSRegSet prevAnticIn = AnticIn[MBB]; - AnticIn[MBB] = CSRUsed[MBB] | AnticOut[MBB]; - if (prevAnticIn != AnticIn[MBB]) - changed = true; - return changed; -} - -/// calcAvailInOut - calculate the available in/out reg sets -/// for the given MBB by looking backward in the MCFG at MBB's -/// predecessors. -/// -bool PEI::calcAvailInOut(MachineBasicBlock* MBB) { - bool changed = false; - - // AvailIn[MBB] = INTERSECT(AvailOut[P] for P in PREDECESSORS(MBB)) - SmallVector<MachineBasicBlock*, 4> predecessors; - for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), - PE = MBB->pred_end(); PI != PE; ++PI) { - MachineBasicBlock* PRED = *PI; - if (PRED != MBB) - predecessors.push_back(PRED); - } - - unsigned i = 0, e = predecessors.size(); - if (i != e) { - CSRegSet prevAvailIn = AvailIn[MBB]; - MachineBasicBlock* PRED = predecessors[i]; - - AvailIn[MBB] = AvailOut[PRED]; - for (++i; i != e; ++i) { - PRED = predecessors[i]; - AvailIn[MBB] &= AvailOut[PRED]; - } - if (prevAvailIn != AvailIn[MBB]) - changed = true; - } - - // AvailOut[MBB] = UNION(CSRUsed[MBB], AvailIn[MBB]); - CSRegSet prevAvailOut = AvailOut[MBB]; - AvailOut[MBB] = CSRUsed[MBB] | AvailIn[MBB]; - if (prevAvailOut != AvailOut[MBB]) - changed = true; - return changed; -} - -/// calculateAnticAvail - build the sets anticipated and available -/// registers in the MCFG of the current function iteratively, -/// doing a combined forward and backward analysis. -/// -void PEI::calculateAnticAvail(MachineFunction &Fn) { - // Initialize data flow sets. - clearAnticAvailSets(); - - // Calculate Antic{In,Out} and Avail{In,Out} iteratively on the MCFG. - bool changed = true; - unsigned iterations = 0; - while (changed) { - changed = false; - ++iterations; - for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end(); - MBBI != MBBE; ++MBBI) { - MachineBasicBlock* MBB = MBBI; - - // Calculate anticipated in, out regs at MBB from - // anticipated at successors of MBB. - changed |= calcAnticInOut(MBB); - - // Calculate available in, out regs at MBB from - // available at predecessors of MBB. - changed |= calcAvailInOut(MBB); - } - } - - DEBUG({ - if (ShrinkWrapDebugging >= Details) { - dbgs() - << "-----------------------------------------------------------\n" - << " Antic/Avail Sets:\n" - << "-----------------------------------------------------------\n" - << "iterations = " << iterations << "\n" - << "-----------------------------------------------------------\n" - << "MBB | USED | ANTIC_IN | ANTIC_OUT | AVAIL_IN | AVAIL_OUT\n" - << "-----------------------------------------------------------\n"; - - for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end(); - MBBI != MBBE; ++MBBI) { - MachineBasicBlock* MBB = MBBI; - dumpSets(MBB); - } - - dbgs() - << "-----------------------------------------------------------\n"; - } - }); -} - -/// propagateUsesAroundLoop - copy used register info from MBB to all blocks -/// of the loop given by LP and its parent loops. This prevents spills/restores -/// from being placed in the bodies of loops. -/// -void PEI::propagateUsesAroundLoop(MachineBasicBlock* MBB, MachineLoop* LP) { - if (! MBB || !LP) - return; - - std::vector<MachineBasicBlock*> loopBlocks = LP->getBlocks(); - for (unsigned i = 0, e = loopBlocks.size(); i != e; ++i) { - MachineBasicBlock* LBB = loopBlocks[i]; - if (LBB == MBB) - continue; - if (CSRUsed[LBB].contains(CSRUsed[MBB])) - continue; - CSRUsed[LBB] |= CSRUsed[MBB]; - } -} - -/// calculateSets - collect the CSRs used in this function, compute -/// the DF sets that describe the initial minimal regions in the -/// Machine CFG around which CSR spills and restores must be placed. -/// -/// Additionally, this function decides if shrink wrapping should -/// be disabled for the current function, checking the following: -/// 1. the current function has more than 500 MBBs: heuristic limit -/// on function size to reduce compile time impact of the current -/// iterative algorithm. -/// 2. all CSRs are used in the entry block. -/// 3. all CSRs are used in all immediate successors of the entry block. -/// 4. all CSRs are used in a subset of blocks, each of which dominates -/// all return blocks. These blocks, taken as a subgraph of the MCFG, -/// are equivalent to the entry block since all execution paths pass -/// through them. -/// -bool PEI::calculateSets(MachineFunction &Fn) { - // Sets used to compute spill, restore placement sets. - const std::vector<CalleeSavedInfo> CSI = - Fn.getFrameInfo()->getCalleeSavedInfo(); - - // If no CSRs used, we are done. - if (CSI.empty()) { - DEBUG(if (ShrinkWrapThisFunction) - dbgs() << "DISABLED: " << Fn.getName() - << ": uses no callee-saved registers\n"); - return false; - } - - // Save refs to entry and return blocks. - EntryBlock = Fn.begin(); - for (MachineFunction::iterator MBB = Fn.begin(), E = Fn.end(); - MBB != E; ++MBB) - if (isReturnBlock(MBB)) - ReturnBlocks.push_back(MBB); - - // Determine if this function has fast exit paths. - DEBUG(if (ShrinkWrapThisFunction) - findFastExitPath()); - - // Limit shrink wrapping via the current iterative bit vector - // implementation to functions with <= 500 MBBs. - if (Fn.size() > 500) { - DEBUG(if (ShrinkWrapThisFunction) - dbgs() << "DISABLED: " << Fn.getName() - << ": too large (" << Fn.size() << " MBBs)\n"); - ShrinkWrapThisFunction = false; - } - - // Return now if not shrink wrapping. - if (! ShrinkWrapThisFunction) - return false; - - // Collect set of used CSRs. - for (unsigned inx = 0, e = CSI.size(); inx != e; ++inx) { - UsedCSRegs.set(inx); - } - - // Walk instructions in all MBBs, create CSRUsed[] sets, choose - // whether or not to shrink wrap this function. - MachineLoopInfo &LI = getAnalysis<MachineLoopInfo>(); - MachineDominatorTree &DT = getAnalysis<MachineDominatorTree>(); - const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo(); - - bool allCSRUsesInEntryBlock = true; - for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end(); - MBBI != MBBE; ++MBBI) { - MachineBasicBlock* MBB = MBBI; - for (MachineBasicBlock::iterator I = MBB->begin(); I != MBB->end(); ++I) { - for (unsigned inx = 0, e = CSI.size(); inx != e; ++inx) { - unsigned Reg = CSI[inx].getReg(); - // If instruction I reads or modifies Reg, add it to UsedCSRegs, - // CSRUsed map for the current block. - for (unsigned opInx = 0, opEnd = I->getNumOperands(); - opInx != opEnd; ++opInx) { - const MachineOperand &MO = I->getOperand(opInx); - if (! (MO.isReg() && (MO.isUse() || MO.isDef()))) - continue; - unsigned MOReg = MO.getReg(); - if (!MOReg) - continue; - if (MOReg == Reg || - (TargetRegisterInfo::isPhysicalRegister(MOReg) && - TargetRegisterInfo::isPhysicalRegister(Reg) && - TRI->isSubRegister(Reg, MOReg))) { - // CSR Reg is defined/used in block MBB. - CSRUsed[MBB].set(inx); - // Check for uses in EntryBlock. - if (MBB != EntryBlock) - allCSRUsesInEntryBlock = false; - } - } - } - } - - if (CSRUsed[MBB].empty()) - continue; - - // Propagate CSRUsed[MBB] in loops - if (MachineLoop* LP = LI.getLoopFor(MBB)) { - // Add top level loop to work list. - MachineBasicBlock* HDR = getTopLevelLoopPreheader(LP); - MachineLoop* PLP = getTopLevelLoopParent(LP); - - if (! HDR) { - HDR = PLP->getHeader(); - assert(HDR->pred_size() > 0 && "Loop header has no predecessors?"); - MachineBasicBlock::pred_iterator PI = HDR->pred_begin(); - HDR = *PI; - } - TLLoops[HDR] = PLP; - - // Push uses from inside loop to its parent loops, - // or to all other MBBs in its loop. - if (LP->getLoopDepth() > 1) { - for (MachineLoop* PLP = LP->getParentLoop(); PLP; - PLP = PLP->getParentLoop()) { - propagateUsesAroundLoop(MBB, PLP); - } - } else { - propagateUsesAroundLoop(MBB, LP); - } - } - } - - if (allCSRUsesInEntryBlock) { - DEBUG(dbgs() << "DISABLED: " << Fn.getName() - << ": all CSRs used in EntryBlock\n"); - ShrinkWrapThisFunction = false; - } else { - bool allCSRsUsedInEntryFanout = true; - for (MachineBasicBlock::succ_iterator SI = EntryBlock->succ_begin(), - SE = EntryBlock->succ_end(); SI != SE; ++SI) { - MachineBasicBlock* SUCC = *SI; - if (CSRUsed[SUCC] != UsedCSRegs) - allCSRsUsedInEntryFanout = false; - } - if (allCSRsUsedInEntryFanout) { - DEBUG(dbgs() << "DISABLED: " << Fn.getName() - << ": all CSRs used in imm successors of EntryBlock\n"); - ShrinkWrapThisFunction = false; - } - } - - if (ShrinkWrapThisFunction) { - // Check if MBB uses CSRs and dominates all exit nodes. - // Such nodes are equiv. to the entry node w.r.t. - // CSR uses: every path through the function must - // pass through this node. If each CSR is used at least - // once by these nodes, shrink wrapping is disabled. - CSRegSet CSRUsedInChokePoints; - for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end(); - MBBI != MBBE; ++MBBI) { - MachineBasicBlock* MBB = MBBI; - if (MBB == EntryBlock || CSRUsed[MBB].empty() || MBB->succ_size() < 1) - continue; - bool dominatesExitNodes = true; - for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri) - if (! DT.dominates(MBB, ReturnBlocks[ri])) { - dominatesExitNodes = false; - break; - } - if (dominatesExitNodes) { - CSRUsedInChokePoints |= CSRUsed[MBB]; - if (CSRUsedInChokePoints == UsedCSRegs) { - DEBUG(dbgs() << "DISABLED: " << Fn.getName() - << ": all CSRs used in choke point(s) at " - << getBasicBlockName(MBB) << "\n"); - ShrinkWrapThisFunction = false; - break; - } - } - } - } - - // Return now if we have decided not to apply shrink wrapping - // to the current function. - if (! ShrinkWrapThisFunction) - return false; - - DEBUG({ - dbgs() << "ENABLED: " << Fn.getName(); - if (HasFastExitPath) - dbgs() << " (fast exit path)"; - dbgs() << "\n"; - if (ShrinkWrapDebugging >= BasicInfo) { - dbgs() << "------------------------------" - << "-----------------------------\n"; - dbgs() << "UsedCSRegs = " << stringifyCSRegSet(UsedCSRegs) << "\n"; - if (ShrinkWrapDebugging >= Details) { - dbgs() << "------------------------------" - << "-----------------------------\n"; - dumpAllUsed(); - } - } - }); - - // Build initial DF sets to determine minimal regions in the - // Machine CFG around which CSRs must be spilled and restored. - calculateAnticAvail(Fn); - - return true; -} - -/// addUsesForMEMERegion - add uses of CSRs spilled or restored in -/// multi-entry, multi-exit (MEME) regions so spill and restore -/// placement will not break code that enters or leaves a -/// shrink-wrapped region by inducing spills with no matching -/// restores or restores with no matching spills. A MEME region -/// is a subgraph of the MCFG with multiple entry edges, multiple -/// exit edges, or both. This code propagates use information -/// through the MCFG until all paths requiring spills and restores -/// _outside_ the computed minimal placement regions have been covered. -/// -bool PEI::addUsesForMEMERegion(MachineBasicBlock* MBB, - SmallVectorImpl<MachineBasicBlock *> &blks) { - if (MBB->succ_size() < 2 && MBB->pred_size() < 2) { - bool processThisBlock = false; - for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(), - SE = MBB->succ_end(); SI != SE; ++SI) { - MachineBasicBlock* SUCC = *SI; - if (SUCC->pred_size() > 1) { - processThisBlock = true; - break; - } - } - if (!CSRRestore[MBB].empty() && MBB->succ_size() > 0) { - for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), - PE = MBB->pred_end(); PI != PE; ++PI) { - MachineBasicBlock* PRED = *PI; - if (PRED->succ_size() > 1) { - processThisBlock = true; - break; - } - } - } - if (! processThisBlock) - return false; - } - - CSRegSet prop; - if (!CSRSave[MBB].empty()) - prop = CSRSave[MBB]; - else if (!CSRRestore[MBB].empty()) - prop = CSRRestore[MBB]; - else - prop = CSRUsed[MBB]; - if (prop.empty()) - return false; - - // Propagate selected bits to successors, predecessors of MBB. - bool addedUses = false; - for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(), - SE = MBB->succ_end(); SI != SE; ++SI) { - MachineBasicBlock* SUCC = *SI; - // Self-loop - if (SUCC == MBB) - continue; - if (! CSRUsed[SUCC].contains(prop)) { - CSRUsed[SUCC] |= prop; - addedUses = true; - blks.push_back(SUCC); - DEBUG(if (ShrinkWrapDebugging >= Iterations) - dbgs() << getBasicBlockName(MBB) - << "(" << stringifyCSRegSet(prop) << ")->" - << "successor " << getBasicBlockName(SUCC) << "\n"); - } - } - for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), - PE = MBB->pred_end(); PI != PE; ++PI) { - MachineBasicBlock* PRED = *PI; - // Self-loop - if (PRED == MBB) - continue; - if (! CSRUsed[PRED].contains(prop)) { - CSRUsed[PRED] |= prop; - addedUses = true; - blks.push_back(PRED); - DEBUG(if (ShrinkWrapDebugging >= Iterations) - dbgs() << getBasicBlockName(MBB) - << "(" << stringifyCSRegSet(prop) << ")->" - << "predecessor " << getBasicBlockName(PRED) << "\n"); - } - } - return addedUses; -} - -/// addUsesForTopLevelLoops - add uses for CSRs used inside top -/// level loops to the exit blocks of those loops. -/// -bool PEI::addUsesForTopLevelLoops(SmallVectorImpl<MachineBasicBlock *> &blks) { - bool addedUses = false; - - // Place restores for top level loops where needed. - for (DenseMap<MachineBasicBlock*, MachineLoop*>::iterator - I = TLLoops.begin(), E = TLLoops.end(); I != E; ++I) { - MachineBasicBlock* MBB = I->first; - MachineLoop* LP = I->second; - MachineBasicBlock* HDR = LP->getHeader(); - SmallVector<MachineBasicBlock*, 4> exitBlocks; - CSRegSet loopSpills; - - loopSpills = CSRSave[MBB]; - if (CSRSave[MBB].empty()) { - loopSpills = CSRUsed[HDR]; - assert(!loopSpills.empty() && "No CSRs used in loop?"); - } else if (CSRRestore[MBB].contains(CSRSave[MBB])) - continue; - - LP->getExitBlocks(exitBlocks); - assert(exitBlocks.size() > 0 && "Loop has no top level exit blocks?"); - for (unsigned i = 0, e = exitBlocks.size(); i != e; ++i) { - MachineBasicBlock* EXB = exitBlocks[i]; - if (! CSRUsed[EXB].contains(loopSpills)) { - CSRUsed[EXB] |= loopSpills; - addedUses = true; - DEBUG(if (ShrinkWrapDebugging >= Iterations) - dbgs() << "LOOP " << getBasicBlockName(MBB) - << "(" << stringifyCSRegSet(loopSpills) << ")->" - << getBasicBlockName(EXB) << "\n"); - if (EXB->succ_size() > 1 || EXB->pred_size() > 1) - blks.push_back(EXB); - } - } - } - return addedUses; -} - -/// calcSpillPlacements - determine which CSRs should be spilled -/// in MBB using AnticIn sets of MBB's predecessors, keeping track -/// of changes to spilled reg sets. Add MBB to the set of blocks -/// that need to be processed for propagating use info to cover -/// multi-entry/exit regions. -/// -bool PEI::calcSpillPlacements(MachineBasicBlock* MBB, - SmallVectorImpl<MachineBasicBlock *> &blks, - CSRegBlockMap &prevSpills) { - bool placedSpills = false; - // Intersect (CSRegs - AnticIn[P]) for P in Predecessors(MBB) - CSRegSet anticInPreds; - SmallVector<MachineBasicBlock*, 4> predecessors; - for (MachineBasicBlock::pred_iterator PI = MBB->pred_begin(), - PE = MBB->pred_end(); PI != PE; ++PI) { - MachineBasicBlock* PRED = *PI; - if (PRED != MBB) - predecessors.push_back(PRED); - } - unsigned i = 0, e = predecessors.size(); - if (i != e) { - MachineBasicBlock* PRED = predecessors[i]; - anticInPreds = UsedCSRegs - AnticIn[PRED]; - for (++i; i != e; ++i) { - PRED = predecessors[i]; - anticInPreds &= (UsedCSRegs - AnticIn[PRED]); - } - } else { - // Handle uses in entry blocks (which have no predecessors). - // This is necessary because the DFA formulation assumes the - // entry and (multiple) exit nodes cannot have CSR uses, which - // is not the case in the real world. - anticInPreds = UsedCSRegs; - } - // Compute spills required at MBB: - CSRSave[MBB] |= (AnticIn[MBB] - AvailIn[MBB]) & anticInPreds; - - if (! CSRSave[MBB].empty()) { - if (MBB == EntryBlock) { - for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri) - CSRRestore[ReturnBlocks[ri]] |= CSRSave[MBB]; - } else { - // Reset all regs spilled in MBB that are also spilled in EntryBlock. - if (CSRSave[EntryBlock].intersects(CSRSave[MBB])) { - CSRSave[MBB] = CSRSave[MBB] - CSRSave[EntryBlock]; - } - } - } - placedSpills = (CSRSave[MBB] != prevSpills[MBB]); - prevSpills[MBB] = CSRSave[MBB]; - // Remember this block for adding restores to successor - // blocks for multi-entry region. - if (placedSpills) - blks.push_back(MBB); - - DEBUG(if (! CSRSave[MBB].empty() && ShrinkWrapDebugging >= Iterations) - dbgs() << "SAVE[" << getBasicBlockName(MBB) << "] = " - << stringifyCSRegSet(CSRSave[MBB]) << "\n"); - - return placedSpills; -} - -/// calcRestorePlacements - determine which CSRs should be restored -/// in MBB using AvailOut sets of MBB's succcessors, keeping track -/// of changes to restored reg sets. Add MBB to the set of blocks -/// that need to be processed for propagating use info to cover -/// multi-entry/exit regions. -/// -bool PEI::calcRestorePlacements(MachineBasicBlock* MBB, - SmallVectorImpl<MachineBasicBlock *> &blks, - CSRegBlockMap &prevRestores) { - bool placedRestores = false; - // Intersect (CSRegs - AvailOut[S]) for S in Successors(MBB) - CSRegSet availOutSucc; - SmallVector<MachineBasicBlock*, 4> successors; - for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(), - SE = MBB->succ_end(); SI != SE; ++SI) { - MachineBasicBlock* SUCC = *SI; - if (SUCC != MBB) - successors.push_back(SUCC); - } - unsigned i = 0, e = successors.size(); - if (i != e) { - MachineBasicBlock* SUCC = successors[i]; - availOutSucc = UsedCSRegs - AvailOut[SUCC]; - for (++i; i != e; ++i) { - SUCC = successors[i]; - availOutSucc &= (UsedCSRegs - AvailOut[SUCC]); - } - } else { - if (! CSRUsed[MBB].empty() || ! AvailOut[MBB].empty()) { - // Handle uses in return blocks (which have no successors). - // This is necessary because the DFA formulation assumes the - // entry and (multiple) exit nodes cannot have CSR uses, which - // is not the case in the real world. - availOutSucc = UsedCSRegs; - } - } - // Compute restores required at MBB: - CSRRestore[MBB] |= (AvailOut[MBB] - AnticOut[MBB]) & availOutSucc; - - // Postprocess restore placements at MBB. - // Remove the CSRs that are restored in the return blocks. - // Lest this be confusing, note that: - // CSRSave[EntryBlock] == CSRRestore[B] for all B in ReturnBlocks. - if (MBB->succ_size() && ! CSRRestore[MBB].empty()) { - if (! CSRSave[EntryBlock].empty()) - CSRRestore[MBB] = CSRRestore[MBB] - CSRSave[EntryBlock]; - } - placedRestores = (CSRRestore[MBB] != prevRestores[MBB]); - prevRestores[MBB] = CSRRestore[MBB]; - // Remember this block for adding saves to predecessor - // blocks for multi-entry region. - if (placedRestores) - blks.push_back(MBB); - - DEBUG(if (! CSRRestore[MBB].empty() && ShrinkWrapDebugging >= Iterations) - dbgs() << "RESTORE[" << getBasicBlockName(MBB) << "] = " - << stringifyCSRegSet(CSRRestore[MBB]) << "\n"); - - return placedRestores; -} - -/// placeSpillsAndRestores - place spills and restores of CSRs -/// used in MBBs in minimal regions that contain the uses. -/// -void PEI::placeSpillsAndRestores(MachineFunction &Fn) { - CSRegBlockMap prevCSRSave; - CSRegBlockMap prevCSRRestore; - SmallVector<MachineBasicBlock*, 4> cvBlocks, ncvBlocks; - bool changed = true; - unsigned iterations = 0; - - // Iterate computation of spill and restore placements in the MCFG until: - // 1. CSR use info has been fully propagated around the MCFG, and - // 2. computation of CSRSave[], CSRRestore[] reach fixed points. - while (changed) { - changed = false; - ++iterations; - - DEBUG(if (ShrinkWrapDebugging >= Iterations) - dbgs() << "iter " << iterations - << " --------------------------------------------------\n"); - - // Calculate CSR{Save,Restore} sets using Antic, Avail on the MCFG, - // which determines the placements of spills and restores. - // Keep track of changes to spills, restores in each iteration to - // minimize the total iterations. - bool SRChanged = false; - for (MachineFunction::iterator MBBI = Fn.begin(), MBBE = Fn.end(); - MBBI != MBBE; ++MBBI) { - MachineBasicBlock* MBB = MBBI; - - // Place spills for CSRs in MBB. - SRChanged |= calcSpillPlacements(MBB, cvBlocks, prevCSRSave); - - // Place restores for CSRs in MBB. - SRChanged |= calcRestorePlacements(MBB, cvBlocks, prevCSRRestore); - } - - // Add uses of CSRs used inside loops where needed. - changed |= addUsesForTopLevelLoops(cvBlocks); - - // Add uses for CSRs spilled or restored at branch, join points. - if (changed || SRChanged) { - while (! cvBlocks.empty()) { - MachineBasicBlock* MBB = cvBlocks.pop_back_val(); - changed |= addUsesForMEMERegion(MBB, ncvBlocks); - } - if (! ncvBlocks.empty()) { - cvBlocks = ncvBlocks; - ncvBlocks.clear(); - } - } - - if (changed) { - calculateAnticAvail(Fn); - CSRSave.clear(); - CSRRestore.clear(); - } - } - - // Check for effectiveness: - // SR0 = {r | r in CSRSave[EntryBlock], CSRRestore[RB], RB in ReturnBlocks} - // numSRReduced = |(UsedCSRegs - SR0)|, approx. SR0 by CSRSave[EntryBlock] - // Gives a measure of how many CSR spills have been moved from EntryBlock - // to minimal regions enclosing their uses. - CSRegSet notSpilledInEntryBlock = (UsedCSRegs - CSRSave[EntryBlock]); - unsigned numSRReducedThisFunc = notSpilledInEntryBlock.count(); - numSRReduced += numSRReducedThisFunc; - DEBUG(if (ShrinkWrapDebugging >= BasicInfo) { - dbgs() << "-----------------------------------------------------------\n"; - dbgs() << "total iterations = " << iterations << " ( " - << Fn.getName() - << " " << numSRReducedThisFunc - << " " << Fn.size() - << " )\n"; - dbgs() << "-----------------------------------------------------------\n"; - dumpSRSets(); - dbgs() << "-----------------------------------------------------------\n"; - if (numSRReducedThisFunc) - verifySpillRestorePlacement(); - }); -} - -// Debugging methods. -#ifndef NDEBUG -/// findFastExitPath - debugging method used to detect functions -/// with at least one path from the entry block to a return block -/// directly or which has a very small number of edges. -/// -void PEI::findFastExitPath() { - if (! EntryBlock) - return; - // Fina a path from EntryBlock to any return block that does not branch: - // Entry - // | ... - // v | - // B1<-----+ - // | - // v - // Return - for (MachineBasicBlock::succ_iterator SI = EntryBlock->succ_begin(), - SE = EntryBlock->succ_end(); SI != SE; ++SI) { - MachineBasicBlock* SUCC = *SI; - - // Assume positive, disprove existence of fast path. - HasFastExitPath = true; - - // Check the immediate successors. - if (isReturnBlock(SUCC)) { - if (ShrinkWrapDebugging >= BasicInfo) - dbgs() << "Fast exit path: " << getBasicBlockName(EntryBlock) - << "->" << getBasicBlockName(SUCC) << "\n"; - break; - } - // Traverse df from SUCC, look for a branch block. - std::string exitPath = getBasicBlockName(SUCC); - for (df_iterator<MachineBasicBlock*> BI = df_begin(SUCC), - BE = df_end(SUCC); BI != BE; ++BI) { - MachineBasicBlock* SBB = *BI; - // Reject paths with branch nodes. - if (SBB->succ_size() > 1) { - HasFastExitPath = false; - break; - } - exitPath += "->" + getBasicBlockName(SBB); - } - if (HasFastExitPath) { - if (ShrinkWrapDebugging >= BasicInfo) - dbgs() << "Fast exit path: " << getBasicBlockName(EntryBlock) - << "->" << exitPath << "\n"; - break; - } - } -} - -/// verifySpillRestorePlacement - check the current spill/restore -/// sets for safety. Attempt to find spills without restores or -/// restores without spills. -/// Spills: walk df from each MBB in spill set ensuring that -/// all CSRs spilled at MMBB are restored on all paths -/// from MBB to all exit blocks. -/// Restores: walk idf from each MBB in restore set ensuring that -/// all CSRs restored at MBB are spilled on all paths -/// reaching MBB. -/// -void PEI::verifySpillRestorePlacement() { - unsigned numReturnBlocks = 0; - for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end(); - MBBI != MBBE; ++MBBI) { - MachineBasicBlock* MBB = MBBI; - if (isReturnBlock(MBB) || MBB->succ_size() == 0) - ++numReturnBlocks; - } - for (CSRegBlockMap::iterator BI = CSRSave.begin(), - BE = CSRSave.end(); BI != BE; ++BI) { - MachineBasicBlock* MBB = BI->first; - CSRegSet spilled = BI->second; - CSRegSet restored; - - if (spilled.empty()) - continue; - - DEBUG(dbgs() << "SAVE[" << getBasicBlockName(MBB) << "] = " - << stringifyCSRegSet(spilled) - << " RESTORE[" << getBasicBlockName(MBB) << "] = " - << stringifyCSRegSet(CSRRestore[MBB]) << "\n"); - - if (CSRRestore[MBB].intersects(spilled)) { - restored |= (CSRRestore[MBB] & spilled); - } - - // Walk depth first from MBB to find restores of all CSRs spilled at MBB: - // we must find restores for all spills w/no intervening spills on all - // paths from MBB to all return blocks. - for (df_iterator<MachineBasicBlock*> BI = df_begin(MBB), - BE = df_end(MBB); BI != BE; ++BI) { - MachineBasicBlock* SBB = *BI; - if (SBB == MBB) - continue; - // Stop when we encounter spills of any CSRs spilled at MBB that - // have not yet been seen to be restored. - if (CSRSave[SBB].intersects(spilled) && - !restored.contains(CSRSave[SBB] & spilled)) - break; - // Collect the CSRs spilled at MBB that are restored - // at this DF successor of MBB. - if (CSRRestore[SBB].intersects(spilled)) - restored |= (CSRRestore[SBB] & spilled); - // If we are at a retun block, check that the restores - // we have seen so far exhaust the spills at MBB, then - // reset the restores. - if (isReturnBlock(SBB) || SBB->succ_size() == 0) { - if (restored != spilled) { - CSRegSet notRestored = (spilled - restored); - DEBUG(dbgs() << MF->getName() << ": " - << stringifyCSRegSet(notRestored) - << " spilled at " << getBasicBlockName(MBB) - << " are never restored on path to return " - << getBasicBlockName(SBB) << "\n"); - } - restored.clear(); - } - } - } - - // Check restore placements. - for (CSRegBlockMap::iterator BI = CSRRestore.begin(), - BE = CSRRestore.end(); BI != BE; ++BI) { - MachineBasicBlock* MBB = BI->first; - CSRegSet restored = BI->second; - CSRegSet spilled; - - if (restored.empty()) - continue; - - DEBUG(dbgs() << "SAVE[" << getBasicBlockName(MBB) << "] = " - << stringifyCSRegSet(CSRSave[MBB]) - << " RESTORE[" << getBasicBlockName(MBB) << "] = " - << stringifyCSRegSet(restored) << "\n"); - - if (CSRSave[MBB].intersects(restored)) { - spilled |= (CSRSave[MBB] & restored); - } - // Walk inverse depth first from MBB to find spills of all - // CSRs restored at MBB: - for (idf_iterator<MachineBasicBlock*> BI = idf_begin(MBB), - BE = idf_end(MBB); BI != BE; ++BI) { - MachineBasicBlock* PBB = *BI; - if (PBB == MBB) - continue; - // Stop when we encounter restores of any CSRs restored at MBB that - // have not yet been seen to be spilled. - if (CSRRestore[PBB].intersects(restored) && - !spilled.contains(CSRRestore[PBB] & restored)) - break; - // Collect the CSRs restored at MBB that are spilled - // at this DF predecessor of MBB. - if (CSRSave[PBB].intersects(restored)) - spilled |= (CSRSave[PBB] & restored); - } - if (spilled != restored) { - CSRegSet notSpilled = (restored - spilled); - DEBUG(dbgs() << MF->getName() << ": " - << stringifyCSRegSet(notSpilled) - << " restored at " << getBasicBlockName(MBB) - << " are never spilled\n"); - } - } -} - -// Debugging print methods. -std::string PEI::getBasicBlockName(const MachineBasicBlock* MBB) { - if (!MBB) - return ""; - - if (MBB->getBasicBlock()) - return MBB->getBasicBlock()->getName().str(); - - std::ostringstream name; - name << "_MBB_" << MBB->getNumber(); - return name.str(); -} - -std::string PEI::stringifyCSRegSet(const CSRegSet& s) { - const TargetRegisterInfo* TRI = MF->getTarget().getRegisterInfo(); - const std::vector<CalleeSavedInfo> CSI = - MF->getFrameInfo()->getCalleeSavedInfo(); - - std::ostringstream srep; - if (CSI.size() == 0) { - srep << "[]"; - return srep.str(); - } - srep << "["; - CSRegSet::iterator I = s.begin(), E = s.end(); - if (I != E) { - unsigned reg = CSI[*I].getReg(); - srep << TRI->getName(reg); - for (++I; I != E; ++I) { - reg = CSI[*I].getReg(); - srep << ","; - srep << TRI->getName(reg); - } - } - srep << "]"; - return srep.str(); -} - -void PEI::dumpSet(const CSRegSet& s) { - DEBUG(dbgs() << stringifyCSRegSet(s) << "\n"); -} - -void PEI::dumpUsed(MachineBasicBlock* MBB) { - DEBUG({ - if (MBB) - dbgs() << "CSRUsed[" << getBasicBlockName(MBB) << "] = " - << stringifyCSRegSet(CSRUsed[MBB]) << "\n"; - }); -} - -void PEI::dumpAllUsed() { - for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end(); - MBBI != MBBE; ++MBBI) { - MachineBasicBlock* MBB = MBBI; - dumpUsed(MBB); - } -} - -void PEI::dumpSets(MachineBasicBlock* MBB) { - DEBUG({ - if (MBB) - dbgs() << getBasicBlockName(MBB) << " | " - << stringifyCSRegSet(CSRUsed[MBB]) << " | " - << stringifyCSRegSet(AnticIn[MBB]) << " | " - << stringifyCSRegSet(AnticOut[MBB]) << " | " - << stringifyCSRegSet(AvailIn[MBB]) << " | " - << stringifyCSRegSet(AvailOut[MBB]) << "\n"; - }); -} - -void PEI::dumpSets1(MachineBasicBlock* MBB) { - DEBUG({ - if (MBB) - dbgs() << getBasicBlockName(MBB) << " | " - << stringifyCSRegSet(CSRUsed[MBB]) << " | " - << stringifyCSRegSet(AnticIn[MBB]) << " | " - << stringifyCSRegSet(AnticOut[MBB]) << " | " - << stringifyCSRegSet(AvailIn[MBB]) << " | " - << stringifyCSRegSet(AvailOut[MBB]) << " | " - << stringifyCSRegSet(CSRSave[MBB]) << " | " - << stringifyCSRegSet(CSRRestore[MBB]) << "\n"; - }); -} - -void PEI::dumpAllSets() { - for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end(); - MBBI != MBBE; ++MBBI) { - MachineBasicBlock* MBB = MBBI; - dumpSets1(MBB); - } -} - -void PEI::dumpSRSets() { - DEBUG({ - for (MachineFunction::iterator MBB = MF->begin(), E = MF->end(); - MBB != E; ++MBB) { - if (!CSRSave[MBB].empty()) { - dbgs() << "SAVE[" << getBasicBlockName(MBB) << "] = " - << stringifyCSRegSet(CSRSave[MBB]); - if (CSRRestore[MBB].empty()) - dbgs() << '\n'; - } - - if (!CSRRestore[MBB].empty() && !CSRSave[MBB].empty()) - dbgs() << " " - << "RESTORE[" << getBasicBlockName(MBB) << "] = " - << stringifyCSRegSet(CSRRestore[MBB]) << "\n"; - } - }); -} -#endif |