2002-05-10 22:44:58 +00:00
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//===-- LICM.cpp - Loop Invariant Code Motion Pass ------------------------===//
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2005-04-21 23:48:37 +00:00
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//
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2003-10-20 19:43:21 +00:00
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// The LLVM Compiler Infrastructure
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//
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2007-12-29 20:36:04 +00:00
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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2005-04-21 23:48:37 +00:00
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//
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2003-10-20 19:43:21 +00:00
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//===----------------------------------------------------------------------===//
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2002-05-10 22:44:58 +00:00
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//
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2003-12-09 17:18:00 +00:00
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// This pass performs loop invariant code motion, attempting to remove as much
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// code from the body of a loop as possible. It does this by either hoisting
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// code into the preheader block, or by sinking code to the exit blocks if it is
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// safe. This pass also promotes must-aliased memory locations in the loop to
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2003-12-19 07:22:45 +00:00
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// live in registers, thus hoisting and sinking "invariant" loads and stores.
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2003-12-09 17:18:00 +00:00
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//
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// This pass uses alias analysis for two purposes:
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2003-02-24 03:52:32 +00:00
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//
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2004-05-23 21:20:19 +00:00
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// 1. Moving loop invariant loads and calls out of loops. If we can determine
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// that a load or call inside of a loop never aliases anything stored to,
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// we can hoist it or sink it like any other instruction.
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2003-02-24 03:52:32 +00:00
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// 2. Scalar Promotion of Memory - If there is a store instruction inside of
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// the loop, we try to move the store to happen AFTER the loop instead of
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// inside of the loop. This can only happen if a few conditions are true:
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// A. The pointer stored through is loop invariant
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// B. There are no stores or loads in the loop which _may_ alias the
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// pointer. There are no calls in the loop which mod/ref the pointer.
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// If these conditions are true, we can promote the loads and stores in the
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// loop of the pointer to use a temporary alloca'd variable. We then use
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2010-08-29 06:43:52 +00:00
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// the SSAUpdater to construct the appropriate SSA form for the value.
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2002-05-10 22:44:58 +00:00
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//
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//===----------------------------------------------------------------------===//
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2005-03-23 21:00:12 +00:00
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#define DEBUG_TYPE "licm"
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2002-05-10 22:44:58 +00:00
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#include "llvm/Transforms/Scalar.h"
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2012-12-03 16:50:05 +00:00
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#include "llvm/ADT/Statistic.h"
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2002-08-22 21:39:55 +00:00
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#include "llvm/Analysis/AliasAnalysis.h"
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2003-03-03 23:32:45 +00:00
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#include "llvm/Analysis/AliasSetTracker.h"
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2010-08-31 23:00:16 +00:00
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#include "llvm/Analysis/ConstantFolding.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/LoopPass.h"
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2014-01-24 01:59:49 +00:00
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#include "llvm/Analysis/ScalarEvolution.h"
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2011-12-14 23:49:11 +00:00
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#include "llvm/Analysis/ValueTracking.h"
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2014-03-04 11:45:46 +00:00
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#include "llvm/IR/CFG.h"
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2013-01-02 11:36:10 +00:00
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/DerivedTypes.h"
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2014-01-13 09:26:24 +00:00
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#include "llvm/IR/Dominators.h"
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2013-01-02 11:36:10 +00:00
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/IntrinsicInst.h"
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#include "llvm/IR/LLVMContext.h"
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2013-01-05 16:44:07 +00:00
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#include "llvm/IR/Metadata.h"
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2014-03-04 12:09:19 +00:00
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#include "llvm/IR/PredIteratorCache.h"
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2004-09-01 22:55:40 +00:00
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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2012-12-03 16:50:05 +00:00
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetLibraryInfo.h"
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#include "llvm/Transforms/Utils/Local.h"
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2014-01-25 04:07:24 +00:00
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#include "llvm/Transforms/Utils/LoopUtils.h"
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2012-12-03 16:50:05 +00:00
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#include "llvm/Transforms/Utils/SSAUpdater.h"
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2002-05-10 22:44:58 +00:00
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#include <algorithm>
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2003-12-09 17:18:00 +00:00
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using namespace llvm;
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2003-11-11 22:41:34 +00:00
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2006-12-19 21:40:18 +00:00
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STATISTIC(NumSunk , "Number of instructions sunk out of loop");
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STATISTIC(NumHoisted , "Number of instructions hoisted out of loop");
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STATISTIC(NumMovedLoads, "Number of load insts hoisted or sunk");
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STATISTIC(NumMovedCalls, "Number of call insts hoisted or sunk");
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STATISTIC(NumPromoted , "Number of memory locations promoted to registers");
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2008-05-13 00:00:25 +00:00
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static cl::opt<bool>
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DisablePromotion("disable-licm-promotion", cl::Hidden,
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cl::desc("Disable memory promotion in LICM pass"));
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2003-02-24 03:52:32 +00:00
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2008-05-13 00:00:25 +00:00
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namespace {
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2009-09-02 06:11:42 +00:00
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struct LICM : public LoopPass {
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2007-05-06 13:37:16 +00:00
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static char ID; // Pass identification, replacement for typeid
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2010-10-19 17:21:58 +00:00
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LICM() : LoopPass(ID) {
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initializeLICMPass(*PassRegistry::getPassRegistry());
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}
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2007-05-01 21:15:47 +00:00
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2014-03-05 09:10:37 +00:00
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bool runOnLoop(Loop *L, LPPassManager &LPM) override;
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2002-05-10 22:44:58 +00:00
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2002-09-26 16:52:07 +00:00
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/// This transformation requires natural loop information & requires that
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/// loop preheaders be inserted into the CFG...
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///
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2014-03-05 09:10:37 +00:00
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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2002-10-21 20:00:28 +00:00
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AU.setPreservesCFG();
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2014-01-13 13:07:17 +00:00
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AU.addRequired<DominatorTreeWrapperPass>();
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2010-07-16 17:58:45 +00:00
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AU.addRequired<LoopInfo>();
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AU.addRequiredID(LoopSimplifyID);
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2014-01-25 04:07:24 +00:00
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AU.addPreservedID(LoopSimplifyID);
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AU.addRequiredID(LCSSAID);
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AU.addPreservedID(LCSSAID);
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2002-08-22 21:39:55 +00:00
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AU.addRequired<AliasAnalysis>();
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2010-08-29 07:02:56 +00:00
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AU.addPreserved<AliasAnalysis>();
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2014-01-24 01:59:49 +00:00
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AU.addPreserved<ScalarEvolution>();
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2011-12-02 01:26:24 +00:00
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AU.addRequired<TargetLibraryInfo>();
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2002-05-10 22:44:58 +00:00
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}
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2012-12-04 05:41:27 +00:00
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using llvm::Pass::doFinalization;
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2014-03-05 09:10:37 +00:00
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bool doFinalization() override {
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2010-08-29 17:46:00 +00:00
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assert(LoopToAliasSetMap.empty() && "Didn't free loop alias sets");
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2007-03-07 04:41:30 +00:00
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return false;
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}
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2002-05-10 22:44:58 +00:00
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private:
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2003-02-24 03:52:32 +00:00
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AliasAnalysis *AA; // Current AliasAnalysis information
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2003-12-09 17:18:00 +00:00
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LoopInfo *LI; // Current LoopInfo
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2010-08-29 06:49:44 +00:00
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DominatorTree *DT; // Dominator Tree for the current Loop.
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2003-12-09 17:18:00 +00:00
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2014-02-24 23:12:18 +00:00
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const DataLayout *DL; // DataLayout for constant folding.
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2011-12-02 01:26:24 +00:00
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TargetLibraryInfo *TLI; // TargetLibraryInfo for constant folding.
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2010-08-29 17:46:00 +00:00
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// State that is updated as we process loops.
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2003-02-24 03:52:32 +00:00
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bool Changed; // Set to true when we change anything.
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BasicBlock *Preheader; // The preheader block of the current loop...
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Loop *CurLoop; // The current loop we are working on...
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2003-03-03 23:32:45 +00:00
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AliasSetTracker *CurAST; // AliasSet information for the current loop...
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2012-09-04 10:25:04 +00:00
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bool MayThrow; // The current loop contains an instruction which
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// may throw, thus preventing code motion of
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// instructions with side effects.
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2010-08-29 17:46:00 +00:00
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DenseMap<Loop*, AliasSetTracker*> LoopToAliasSetMap;
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2002-05-10 22:44:58 +00:00
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2007-07-31 08:01:41 +00:00
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/// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info.
|
2014-03-05 09:10:37 +00:00
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void cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To,
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Loop *L) override;
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2007-07-31 08:01:41 +00:00
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/// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias
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/// set.
|
2014-03-05 09:10:37 +00:00
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void deleteAnalysisValue(Value *V, Loop *L) override;
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2007-07-31 08:01:41 +00:00
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2003-12-19 07:22:45 +00:00
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/// SinkRegion - Walk the specified region of the CFG (defined by all blocks
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/// dominated by the specified block, and that are in the current loop) in
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2007-04-24 06:40:39 +00:00
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/// reverse depth first order w.r.t the DominatorTree. This allows us to
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2003-12-19 07:22:45 +00:00
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/// visit uses before definitions, allowing us to sink a loop body in one
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/// pass without iteration.
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///
|
2007-06-04 00:32:22 +00:00
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void SinkRegion(DomTreeNode *N);
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2003-12-19 07:22:45 +00:00
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2002-09-29 21:46:09 +00:00
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/// HoistRegion - Walk the specified region of the CFG (defined by all
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/// blocks dominated by the specified block, and that are in the current
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2007-04-24 06:40:39 +00:00
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/// loop) in depth first order w.r.t the DominatorTree. This allows us to
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2003-10-10 17:57:28 +00:00
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/// visit definitions before uses, allowing us to hoist a loop body in one
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2002-09-29 21:46:09 +00:00
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/// pass without iteration.
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///
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2007-06-04 00:32:22 +00:00
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void HoistRegion(DomTreeNode *N);
|
2002-09-29 21:46:09 +00:00
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2002-09-29 22:26:07 +00:00
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/// inSubLoop - Little predicate that returns true if the specified basic
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/// block is in a subloop of the current one, not the current one itself.
|
2002-09-26 16:52:07 +00:00
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///
|
2002-09-29 22:26:07 +00:00
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bool inSubLoop(BasicBlock *BB) {
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assert(CurLoop->contains(BB) && "Only valid if BB is IN the loop");
|
2011-01-02 18:53:08 +00:00
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return LI->getLoopFor(BB) != CurLoop;
|
2002-05-10 22:44:58 +00:00
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}
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2003-12-10 06:41:05 +00:00
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/// sink - When an instruction is found to only be used outside of the loop,
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/// this function moves it to the exit blocks and patches up SSA form as
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/// needed.
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///
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void sink(Instruction &I);
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2002-09-26 16:52:07 +00:00
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/// hoist - When an instruction is found to only use loop invariant operands
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/// that is safe to hoist, this instruction is called to do the dirty work.
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///
|
2002-06-25 16:13:24 +00:00
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void hoist(Instruction &I);
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2002-05-10 22:44:58 +00:00
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2003-12-10 06:41:05 +00:00
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/// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it
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/// is not a trapping instruction or if it is a trapping instruction and is
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/// guaranteed to execute.
|
2003-08-05 18:45:46 +00:00
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///
|
2003-12-10 06:41:05 +00:00
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bool isSafeToExecuteUnconditionally(Instruction &I);
|
2003-08-05 18:45:46 +00:00
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|
2011-07-20 21:37:47 +00:00
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/// isGuaranteedToExecute - Check that the instruction is guaranteed to
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/// execute.
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///
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bool isGuaranteedToExecute(Instruction &I);
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|
2002-09-26 16:52:07 +00:00
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/// pointerInvalidatedByLoop - Return true if the body of this loop may
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/// store into the memory location pointed to by V.
|
2005-04-21 23:48:37 +00:00
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///
|
2010-10-19 22:54:46 +00:00
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bool pointerInvalidatedByLoop(Value *V, uint64_t Size,
|
2010-10-18 20:44:50 +00:00
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const MDNode *TBAAInfo) {
|
2003-03-03 23:32:45 +00:00
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// Check to see if any of the basic blocks in CurLoop invalidate *V.
|
2010-10-18 20:44:50 +00:00
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return CurAST->getAliasSetForPointer(V, Size, TBAAInfo).isMod();
|
2003-02-24 03:52:32 +00:00
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}
|
2002-08-22 21:39:55 +00:00
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|
2003-12-10 06:41:05 +00:00
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bool canSinkOrHoistInst(Instruction &I);
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bool isNotUsedInLoop(Instruction &I);
|
2002-05-10 22:44:58 +00:00
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|
2012-08-08 00:00:26 +00:00
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void PromoteAliasSet(AliasSet &AS,
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SmallVectorImpl<BasicBlock*> &ExitBlocks,
|
2014-02-11 12:52:27 +00:00
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SmallVectorImpl<Instruction*> &InsertPts,
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PredIteratorCache &PIC);
|
2002-05-10 22:44:58 +00:00
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};
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}
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|
2008-05-13 00:00:25 +00:00
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char LICM::ID = 0;
|
2010-10-12 19:48:12 +00:00
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INITIALIZE_PASS_BEGIN(LICM, "licm", "Loop Invariant Code Motion", false, false)
|
2014-01-13 13:07:17 +00:00
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INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
|
2010-10-12 19:48:12 +00:00
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INITIALIZE_PASS_DEPENDENCY(LoopInfo)
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INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
|
2014-01-25 04:07:24 +00:00
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INITIALIZE_PASS_DEPENDENCY(LCSSA)
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INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
|
2011-12-02 01:26:24 +00:00
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INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
|
2010-10-12 19:48:12 +00:00
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INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
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INITIALIZE_PASS_END(LICM, "licm", "Loop Invariant Code Motion", false, false)
|
2008-05-13 00:00:25 +00:00
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|
2008-10-22 23:32:42 +00:00
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Pass *llvm::createLICMPass() { return new LICM(); }
|
2002-05-10 22:44:58 +00:00
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|
2007-07-31 16:52:25 +00:00
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/// Hoist expressions out of the specified loop. Note, alias info for inner
|
2011-07-06 19:20:02 +00:00
|
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|
/// loop is not preserved so it is not a good idea to run LICM multiple
|
2007-07-31 16:52:25 +00:00
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/// times on one loop.
|
2002-09-26 16:52:07 +00:00
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///
|
2007-03-07 04:41:30 +00:00
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bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) {
|
2014-02-06 00:07:05 +00:00
|
|
|
if (skipOptnoneFunction(L))
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|
return false;
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|
2003-02-24 03:52:32 +00:00
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Changed = false;
|
2002-05-10 22:44:58 +00:00
|
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|
2003-02-24 03:52:32 +00:00
|
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// Get our Loop and Alias Analysis information...
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LI = &getAnalysis<LoopInfo>();
|
2002-08-22 21:39:55 +00:00
|
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|
AA = &getAnalysis<AliasAnalysis>();
|
2014-01-13 13:07:17 +00:00
|
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|
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
|
2002-08-22 21:39:55 +00:00
|
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|
2014-02-25 17:30:31 +00:00
|
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|
DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
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|
DL = DLP ? &DLP->getDataLayout() : 0;
|
2011-12-02 01:26:24 +00:00
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|
TLI = &getAnalysis<TargetLibraryInfo>();
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|
2014-02-11 12:52:27 +00:00
|
|
|
assert(L->isLCSSAForm(*DT) && "Loop is not in LCSSA form.");
|
|
|
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|
2007-03-07 04:41:30 +00:00
|
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|
CurAST = new AliasSetTracker(*AA);
|
2010-08-29 17:46:00 +00:00
|
|
|
// Collect Alias info from subloops.
|
2007-03-07 04:41:30 +00:00
|
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|
for (Loop::iterator LoopItr = L->begin(), LoopItrE = L->end();
|
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|
LoopItr != LoopItrE; ++LoopItr) {
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|
Loop *InnerL = *LoopItr;
|
2010-08-29 17:46:00 +00:00
|
|
|
AliasSetTracker *InnerAST = LoopToAliasSetMap[InnerL];
|
|
|
|
assert(InnerAST && "Where is my AST?");
|
2002-09-26 16:52:07 +00:00
|
|
|
|
2007-03-07 04:41:30 +00:00
|
|
|
// What if InnerLoop was modified by other passes ?
|
|
|
|
CurAST->add(*InnerAST);
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2010-08-29 17:46:00 +00:00
|
|
|
// Once we've incorporated the inner loop's AST into ours, we don't need the
|
|
|
|
// subloop's anymore.
|
|
|
|
delete InnerAST;
|
|
|
|
LoopToAliasSetMap.erase(InnerL);
|
2003-02-24 03:52:32 +00:00
|
|
|
}
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2002-05-10 22:44:58 +00:00
|
|
|
CurLoop = L;
|
|
|
|
|
2002-09-26 19:40:25 +00:00
|
|
|
// Get the preheader block to move instructions into...
|
|
|
|
Preheader = L->getLoopPreheader();
|
|
|
|
|
2003-02-24 03:52:32 +00:00
|
|
|
// Loop over the body of this loop, looking for calls, invokes, and stores.
|
2003-03-03 23:32:45 +00:00
|
|
|
// Because subloops have already been incorporated into AST, we skip blocks in
|
2003-02-24 03:52:32 +00:00
|
|
|
// subloops.
|
|
|
|
//
|
2008-06-22 20:18:58 +00:00
|
|
|
for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
|
|
|
|
I != E; ++I) {
|
|
|
|
BasicBlock *BB = *I;
|
2010-08-29 17:46:00 +00:00
|
|
|
if (LI->getLoopFor(BB) == L) // Ignore blocks in subloops.
|
2008-06-22 20:18:58 +00:00
|
|
|
CurAST->add(*BB); // Incorporate the specified basic block
|
|
|
|
}
|
2003-02-24 03:52:32 +00:00
|
|
|
|
2012-09-04 10:25:04 +00:00
|
|
|
MayThrow = false;
|
|
|
|
// TODO: We've already searched for instructions which may throw in subloops.
|
|
|
|
// We may want to reuse this information.
|
|
|
|
for (Loop::block_iterator BB = L->block_begin(), BBE = L->block_end();
|
|
|
|
(BB != BBE) && !MayThrow ; ++BB)
|
|
|
|
for (BasicBlock::iterator I = (*BB)->begin(), E = (*BB)->end();
|
|
|
|
(I != E) && !MayThrow; ++I)
|
|
|
|
MayThrow |= I->mayThrow();
|
|
|
|
|
2002-05-10 22:44:58 +00:00
|
|
|
// We want to visit all of the instructions in this loop... that are not parts
|
|
|
|
// of our subloops (they have already had their invariants hoisted out of
|
|
|
|
// their loop, into this loop, so there is no need to process the BODIES of
|
|
|
|
// the subloops).
|
|
|
|
//
|
2002-09-29 21:46:09 +00:00
|
|
|
// Traverse the body of the loop in depth first order on the dominator tree so
|
|
|
|
// that we are guaranteed to see definitions before we see uses. This allows
|
2007-08-18 15:08:56 +00:00
|
|
|
// us to sink instructions in one pass, without iteration. After sinking
|
2003-12-19 07:22:45 +00:00
|
|
|
// instructions, we perform another pass to hoist them out of the loop.
|
2002-09-29 21:46:09 +00:00
|
|
|
//
|
2009-11-05 21:11:53 +00:00
|
|
|
if (L->hasDedicatedExits())
|
|
|
|
SinkRegion(DT->getNode(L->getHeader()));
|
|
|
|
if (Preheader)
|
|
|
|
HoistRegion(DT->getNode(L->getHeader()));
|
2002-05-10 22:44:58 +00:00
|
|
|
|
2003-02-24 03:52:32 +00:00
|
|
|
// Now that all loop invariants have been removed from the loop, promote any
|
2010-08-29 06:43:52 +00:00
|
|
|
// memory references to scalars that we can.
|
2014-01-24 02:24:47 +00:00
|
|
|
if (!DisablePromotion && (Preheader || L->hasDedicatedExits())) {
|
2012-08-08 00:00:26 +00:00
|
|
|
SmallVector<BasicBlock *, 8> ExitBlocks;
|
|
|
|
SmallVector<Instruction *, 8> InsertPts;
|
2014-02-11 12:52:27 +00:00
|
|
|
PredIteratorCache PIC;
|
2012-08-08 00:00:26 +00:00
|
|
|
|
2010-08-29 06:43:52 +00:00
|
|
|
// Loop over all of the alias sets in the tracker object.
|
|
|
|
for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end();
|
|
|
|
I != E; ++I)
|
2014-02-11 12:52:27 +00:00
|
|
|
PromoteAliasSet(*I, ExitBlocks, InsertPts, PIC);
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2014-02-01 13:35:14 +00:00
|
|
|
// Once we have promoted values across the loop body we have to recursively
|
|
|
|
// reform LCSSA as any nested loop may now have values defined within the
|
|
|
|
// loop used in the outer loop.
|
|
|
|
// FIXME: This is really heavy handed. It would be a bit better to use an
|
|
|
|
// SSAUpdater strategy during promotion that was LCSSA aware and reformed
|
|
|
|
// it as it went.
|
|
|
|
if (Changed)
|
|
|
|
formLCSSARecursively(*L, *DT, getAnalysisIfAvailable<ScalarEvolution>());
|
|
|
|
}
|
|
|
|
|
2014-02-11 12:52:27 +00:00
|
|
|
// Check that neither this loop nor its parent have had LCSSA broken. LICM is
|
|
|
|
// specifically moving instructions across the loop boundary and so it is
|
|
|
|
// especially in need of sanity checking here.
|
|
|
|
assert(L->isLCSSAForm(*DT) && "Loop not left in LCSSA form after LICM!");
|
|
|
|
assert((!L->getParentLoop() || L->getParentLoop()->isLCSSAForm(*DT)) &&
|
|
|
|
"Parent loop not left in LCSSA form after LICM!");
|
2014-01-25 04:07:24 +00:00
|
|
|
|
2002-05-10 22:44:58 +00:00
|
|
|
// Clear out loops state information for the next iteration
|
|
|
|
CurLoop = 0;
|
2002-09-26 19:40:25 +00:00
|
|
|
Preheader = 0;
|
2007-03-07 04:41:30 +00:00
|
|
|
|
2010-08-29 17:46:00 +00:00
|
|
|
// If this loop is nested inside of another one, save the alias information
|
|
|
|
// for when we process the outer loop.
|
|
|
|
if (L->getParentLoop())
|
|
|
|
LoopToAliasSetMap[L] = CurAST;
|
|
|
|
else
|
|
|
|
delete CurAST;
|
2007-03-07 04:41:30 +00:00
|
|
|
return Changed;
|
2002-05-10 22:44:58 +00:00
|
|
|
}
|
|
|
|
|
2003-12-19 07:22:45 +00:00
|
|
|
/// SinkRegion - Walk the specified region of the CFG (defined by all blocks
|
|
|
|
/// dominated by the specified block, and that are in the current loop) in
|
2007-04-24 06:40:39 +00:00
|
|
|
/// reverse depth first order w.r.t the DominatorTree. This allows us to visit
|
2003-12-19 07:22:45 +00:00
|
|
|
/// uses before definitions, allowing us to sink a loop body in one pass without
|
|
|
|
/// iteration.
|
|
|
|
///
|
2007-06-04 00:32:22 +00:00
|
|
|
void LICM::SinkRegion(DomTreeNode *N) {
|
2007-04-24 06:40:39 +00:00
|
|
|
assert(N != 0 && "Null dominator tree node?");
|
|
|
|
BasicBlock *BB = N->getBlock();
|
2003-12-19 07:22:45 +00:00
|
|
|
|
|
|
|
// If this subregion is not in the top level loop at all, exit.
|
|
|
|
if (!CurLoop->contains(BB)) return;
|
|
|
|
|
2010-08-29 18:22:25 +00:00
|
|
|
// We are processing blocks in reverse dfo, so process children first.
|
2007-06-04 00:32:22 +00:00
|
|
|
const std::vector<DomTreeNode*> &Children = N->getChildren();
|
2003-12-19 07:22:45 +00:00
|
|
|
for (unsigned i = 0, e = Children.size(); i != e; ++i)
|
|
|
|
SinkRegion(Children[i]);
|
|
|
|
|
|
|
|
// Only need to process the contents of this block if it is not part of a
|
|
|
|
// subloop (which would already have been processed).
|
|
|
|
if (inSubLoop(BB)) return;
|
|
|
|
|
2003-12-19 08:18:16 +00:00
|
|
|
for (BasicBlock::iterator II = BB->end(); II != BB->begin(); ) {
|
|
|
|
Instruction &I = *--II;
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2010-08-29 18:22:25 +00:00
|
|
|
// If the instruction is dead, we would try to sink it because it isn't used
|
|
|
|
// in the loop, instead, just delete it.
|
2012-08-29 15:32:21 +00:00
|
|
|
if (isInstructionTriviallyDead(&I, TLI)) {
|
2010-08-29 18:42:23 +00:00
|
|
|
DEBUG(dbgs() << "LICM deleting dead inst: " << I << '\n');
|
2010-08-29 18:22:25 +00:00
|
|
|
++II;
|
|
|
|
CurAST->deleteValue(&I);
|
|
|
|
I.eraseFromParent();
|
|
|
|
Changed = true;
|
|
|
|
continue;
|
|
|
|
}
|
2005-04-21 23:48:37 +00:00
|
|
|
|
2003-12-19 07:22:45 +00:00
|
|
|
// Check to see if we can sink this instruction to the exit blocks
|
|
|
|
// of the loop. We can do this if the all users of the instruction are
|
|
|
|
// outside of the loop. In this case, it doesn't even matter if the
|
|
|
|
// operands of the instruction are loop invariant.
|
|
|
|
//
|
2005-03-25 00:22:36 +00:00
|
|
|
if (isNotUsedInLoop(I) && canSinkOrHoistInst(I)) {
|
2003-12-19 08:18:16 +00:00
|
|
|
++II;
|
2003-12-19 07:22:45 +00:00
|
|
|
sink(I);
|
2003-12-19 08:18:16 +00:00
|
|
|
}
|
2003-12-19 07:22:45 +00:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2002-09-29 21:46:09 +00:00
|
|
|
/// HoistRegion - Walk the specified region of the CFG (defined by all blocks
|
|
|
|
/// dominated by the specified block, and that are in the current loop) in depth
|
2007-04-24 06:40:39 +00:00
|
|
|
/// first order w.r.t the DominatorTree. This allows us to visit definitions
|
2002-09-29 21:46:09 +00:00
|
|
|
/// before uses, allowing us to hoist a loop body in one pass without iteration.
|
|
|
|
///
|
2007-06-04 00:32:22 +00:00
|
|
|
void LICM::HoistRegion(DomTreeNode *N) {
|
2007-04-24 06:40:39 +00:00
|
|
|
assert(N != 0 && "Null dominator tree node?");
|
|
|
|
BasicBlock *BB = N->getBlock();
|
2002-09-29 21:46:09 +00:00
|
|
|
|
2002-09-29 22:26:07 +00:00
|
|
|
// If this subregion is not in the top level loop at all, exit.
|
2003-12-09 19:32:44 +00:00
|
|
|
if (!CurLoop->contains(BB)) return;
|
2002-09-29 21:46:09 +00:00
|
|
|
|
2003-12-10 06:41:05 +00:00
|
|
|
// Only need to process the contents of this block if it is not part of a
|
|
|
|
// subloop (which would already have been processed).
|
2003-12-09 19:32:44 +00:00
|
|
|
if (!inSubLoop(BB))
|
2003-12-10 06:41:05 +00:00
|
|
|
for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ) {
|
|
|
|
Instruction &I = *II++;
|
2005-04-21 23:48:37 +00:00
|
|
|
|
2010-08-31 23:00:16 +00:00
|
|
|
// Try constant folding this instruction. If all the operands are
|
|
|
|
// constants, it is technically hoistable, but it would be better to just
|
|
|
|
// fold it.
|
2014-02-21 00:06:31 +00:00
|
|
|
if (Constant *C = ConstantFoldInstruction(&I, DL, TLI)) {
|
2010-08-31 23:00:16 +00:00
|
|
|
DEBUG(dbgs() << "LICM folding inst: " << I << " --> " << *C << '\n');
|
|
|
|
CurAST->copyValue(&I, C);
|
|
|
|
CurAST->deleteValue(&I);
|
|
|
|
I.replaceAllUsesWith(C);
|
|
|
|
I.eraseFromParent();
|
|
|
|
continue;
|
|
|
|
}
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2003-12-19 07:22:45 +00:00
|
|
|
// Try hoisting the instruction out to the preheader. We can only do this
|
|
|
|
// if all of the operands of the instruction are loop invariant and if it
|
|
|
|
// is safe to hoist the instruction.
|
|
|
|
//
|
2010-09-06 01:05:37 +00:00
|
|
|
if (CurLoop->hasLoopInvariantOperands(&I) && canSinkOrHoistInst(I) &&
|
2003-12-19 07:22:45 +00:00
|
|
|
isSafeToExecuteUnconditionally(I))
|
2006-06-26 19:10:05 +00:00
|
|
|
hoist(I);
|
2010-08-31 23:00:16 +00:00
|
|
|
}
|
2002-09-29 21:46:09 +00:00
|
|
|
|
2007-06-04 00:32:22 +00:00
|
|
|
const std::vector<DomTreeNode*> &Children = N->getChildren();
|
2002-09-29 21:46:09 +00:00
|
|
|
for (unsigned i = 0, e = Children.size(); i != e; ++i)
|
2004-06-19 20:23:35 +00:00
|
|
|
HoistRegion(Children[i]);
|
2002-09-29 21:46:09 +00:00
|
|
|
}
|
|
|
|
|
2003-12-10 06:41:05 +00:00
|
|
|
/// canSinkOrHoistInst - Return true if the hoister and sinker can handle this
|
|
|
|
/// instruction.
|
|
|
|
///
|
|
|
|
bool LICM::canSinkOrHoistInst(Instruction &I) {
|
2003-12-09 19:32:44 +00:00
|
|
|
// Loads have extra constraints we have to verify before we can hoist them.
|
|
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
|
2011-08-15 20:52:09 +00:00
|
|
|
if (!LI->isUnordered())
|
|
|
|
return false; // Don't hoist volatile/atomic loads!
|
2003-12-09 19:32:44 +00:00
|
|
|
|
2008-07-23 05:06:28 +00:00
|
|
|
// Loads from constant memory are always safe to move, even if they end up
|
|
|
|
// in the same alias set as something that ends up being modified.
|
2009-11-19 19:00:10 +00:00
|
|
|
if (AA->pointsToConstantMemory(LI->getOperand(0)))
|
2008-07-23 05:06:28 +00:00
|
|
|
return true;
|
2011-12-06 11:50:26 +00:00
|
|
|
if (LI->getMetadata("invariant.load"))
|
2011-11-08 19:30:00 +00:00
|
|
|
return true;
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2003-12-09 19:32:44 +00:00
|
|
|
// Don't hoist loads which have may-aliased stores in loop.
|
2010-10-19 22:54:46 +00:00
|
|
|
uint64_t Size = 0;
|
2004-11-26 21:20:09 +00:00
|
|
|
if (LI->getType()->isSized())
|
2009-07-25 00:48:42 +00:00
|
|
|
Size = AA->getTypeStoreSize(LI->getType());
|
2010-10-18 20:44:50 +00:00
|
|
|
return !pointerInvalidatedByLoop(LI->getOperand(0), Size,
|
|
|
|
LI->getMetadata(LLVMContext::MD_tbaa));
|
2004-03-15 04:11:30 +00:00
|
|
|
} else if (CallInst *CI = dyn_cast<CallInst>(&I)) {
|
2011-05-27 18:37:52 +00:00
|
|
|
// Don't sink or hoist dbg info; it's legal, but not useful.
|
|
|
|
if (isa<DbgInfoIntrinsic>(I))
|
|
|
|
return false;
|
|
|
|
|
|
|
|
// Handle simple cases by querying alias analysis.
|
2007-12-01 07:51:45 +00:00
|
|
|
AliasAnalysis::ModRefBehavior Behavior = AA->getModRefBehavior(CI);
|
|
|
|
if (Behavior == AliasAnalysis::DoesNotAccessMemory)
|
|
|
|
return true;
|
2010-11-09 19:58:21 +00:00
|
|
|
if (AliasAnalysis::onlyReadsMemory(Behavior)) {
|
2007-12-01 07:51:45 +00:00
|
|
|
// If this call only reads from memory and there are no writes to memory
|
|
|
|
// in the loop, we can hoist or sink the call as appropriate.
|
|
|
|
bool FoundMod = false;
|
|
|
|
for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end();
|
|
|
|
I != E; ++I) {
|
|
|
|
AliasSet &AS = *I;
|
|
|
|
if (!AS.isForwardingAliasSet() && AS.isMod()) {
|
|
|
|
FoundMod = true;
|
|
|
|
break;
|
2004-03-15 04:11:30 +00:00
|
|
|
}
|
|
|
|
}
|
2007-12-01 07:51:45 +00:00
|
|
|
if (!FoundMod) return true;
|
2004-03-15 04:11:30 +00:00
|
|
|
}
|
|
|
|
|
2012-09-04 10:25:04 +00:00
|
|
|
// FIXME: This should use mod/ref information to see if we can hoist or
|
|
|
|
// sink the call.
|
2005-04-21 23:48:37 +00:00
|
|
|
|
2004-03-15 04:11:30 +00:00
|
|
|
return false;
|
2003-12-09 19:32:44 +00:00
|
|
|
}
|
|
|
|
|
2012-09-04 10:25:04 +00:00
|
|
|
// Only these instructions are hoistable/sinkable.
|
2013-01-09 18:12:03 +00:00
|
|
|
if (!isa<BinaryOperator>(I) && !isa<CastInst>(I) && !isa<SelectInst>(I) &&
|
|
|
|
!isa<GetElementPtrInst>(I) && !isa<CmpInst>(I) &&
|
|
|
|
!isa<InsertElementInst>(I) && !isa<ExtractElementInst>(I) &&
|
|
|
|
!isa<ShuffleVectorInst>(I) && !isa<ExtractValueInst>(I) &&
|
|
|
|
!isa<InsertValueInst>(I))
|
|
|
|
return false;
|
2012-09-04 10:25:04 +00:00
|
|
|
|
|
|
|
return isSafeToExecuteUnconditionally(I);
|
2003-12-10 06:41:05 +00:00
|
|
|
}
|
|
|
|
|
2014-01-25 04:07:24 +00:00
|
|
|
/// \brief Returns true if a PHINode is a trivially replaceable with an
|
|
|
|
/// Instruction.
|
|
|
|
///
|
|
|
|
/// This is true when all incoming values are that instruction. This pattern
|
|
|
|
/// occurs most often with LCSSA PHI nodes.
|
|
|
|
static bool isTriviallyReplacablePHI(PHINode &PN, Instruction &I) {
|
|
|
|
for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
|
|
|
|
if (PN.getIncomingValue(i) != &I)
|
|
|
|
return false;
|
|
|
|
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
2003-12-10 06:41:05 +00:00
|
|
|
/// isNotUsedInLoop - Return true if the only users of this instruction are
|
|
|
|
/// outside of the loop. If this is true, we can sink the instruction to the
|
|
|
|
/// exit blocks of the loop.
|
|
|
|
///
|
|
|
|
bool LICM::isNotUsedInLoop(Instruction &I) {
|
2014-03-09 03:16:01 +00:00
|
|
|
for (User *U : I.users()) {
|
|
|
|
Instruction *UI = cast<Instruction>(U);
|
|
|
|
if (PHINode *PN = dyn_cast<PHINode>(UI)) {
|
2014-01-25 04:07:24 +00:00
|
|
|
// A PHI node where all of the incoming values are this instruction are
|
|
|
|
// special -- they can just be RAUW'ed with the instruction and thus
|
|
|
|
// don't require a use in the predecessor. This is a particular important
|
|
|
|
// special case because it is the pattern found in LCSSA form.
|
|
|
|
if (isTriviallyReplacablePHI(*PN, I)) {
|
|
|
|
if (CurLoop->contains(PN))
|
|
|
|
return false;
|
|
|
|
else
|
|
|
|
continue;
|
|
|
|
}
|
|
|
|
|
|
|
|
// Otherwise, PHI node uses occur in predecessor blocks if the incoming
|
|
|
|
// values. Check for such a use being inside the loop.
|
2003-12-11 22:23:32 +00:00
|
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
|
|
|
|
if (PN->getIncomingValue(i) == &I)
|
|
|
|
if (CurLoop->contains(PN->getIncomingBlock(i)))
|
|
|
|
return false;
|
2014-01-25 04:07:24 +00:00
|
|
|
|
|
|
|
continue;
|
2003-12-11 22:23:32 +00:00
|
|
|
}
|
2014-01-25 04:07:24 +00:00
|
|
|
|
2014-03-09 03:16:01 +00:00
|
|
|
if (CurLoop->contains(UI))
|
2014-01-25 04:07:24 +00:00
|
|
|
return false;
|
2003-12-11 22:23:32 +00:00
|
|
|
}
|
2003-12-10 06:41:05 +00:00
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
|
|
|
/// sink - When an instruction is found to only be used outside of the loop,
|
2003-12-19 08:18:16 +00:00
|
|
|
/// this function moves it to the exit blocks and patches up SSA form as needed.
|
|
|
|
/// This method is guaranteed to remove the original instruction from its
|
|
|
|
/// position, and may either delete it or move it to outside of the loop.
|
2003-12-10 06:41:05 +00:00
|
|
|
///
|
|
|
|
void LICM::sink(Instruction &I) {
|
2010-07-30 20:27:01 +00:00
|
|
|
DEBUG(dbgs() << "LICM sinking instruction: " << I << "\n");
|
2003-12-10 06:41:05 +00:00
|
|
|
|
2003-12-10 20:43:29 +00:00
|
|
|
if (isa<LoadInst>(I)) ++NumMovedLoads;
|
2004-03-15 04:11:30 +00:00
|
|
|
else if (isa<CallInst>(I)) ++NumMovedCalls;
|
2003-12-10 20:43:29 +00:00
|
|
|
++NumSunk;
|
|
|
|
Changed = true;
|
|
|
|
|
2014-02-11 12:52:27 +00:00
|
|
|
#ifndef NDEBUG
|
|
|
|
SmallVector<BasicBlock *, 32> ExitBlocks;
|
|
|
|
CurLoop->getUniqueExitBlocks(ExitBlocks);
|
|
|
|
SmallPtrSet<BasicBlock *, 32> ExitBlockSet(ExitBlocks.begin(), ExitBlocks.end());
|
|
|
|
#endif
|
|
|
|
|
|
|
|
// If this instruction is only used outside of the loop, then all users are
|
|
|
|
// PHI nodes in exit blocks due to LCSSA form. Just RAUW them with clones of
|
|
|
|
// the instruction.
|
|
|
|
while (!I.use_empty()) {
|
|
|
|
// The user must be a PHI node.
|
2014-03-09 03:16:01 +00:00
|
|
|
PHINode *PN = cast<PHINode>(I.user_back());
|
2014-02-11 12:52:27 +00:00
|
|
|
|
|
|
|
BasicBlock *ExitBlock = PN->getParent();
|
|
|
|
assert(ExitBlockSet.count(ExitBlock) &&
|
|
|
|
"The LCSSA PHI is not in an exit block!");
|
|
|
|
|
|
|
|
Instruction *New = I.clone();
|
|
|
|
ExitBlock->getInstList().insert(ExitBlock->getFirstInsertionPt(), New);
|
|
|
|
if (!I.getName().empty())
|
|
|
|
New->setName(I.getName() + ".le");
|
|
|
|
|
|
|
|
// Build LCSSA PHI nodes for any in-loop operands. Note that this is
|
|
|
|
// particularly cheap because we can rip off the PHI node that we're
|
|
|
|
// replacing for the number and blocks of the predecessors.
|
|
|
|
// OPT: If this shows up in a profile, we can instead finish sinking all
|
|
|
|
// invariant instructions, and then walk their operands to re-establish
|
|
|
|
// LCSSA. That will eliminate creating PHI nodes just to nuke them when
|
|
|
|
// sinking bottom-up.
|
|
|
|
for (User::op_iterator OI = New->op_begin(), OE = New->op_end(); OI != OE;
|
|
|
|
++OI)
|
|
|
|
if (Instruction *OInst = dyn_cast<Instruction>(*OI))
|
|
|
|
if (Loop *OLoop = LI->getLoopFor(OInst->getParent()))
|
|
|
|
if (!OLoop->contains(PN)) {
|
|
|
|
PHINode *OpPN = PHINode::Create(
|
|
|
|
OInst->getType(), PN->getNumIncomingValues(),
|
|
|
|
OInst->getName() + ".lcssa", ExitBlock->begin());
|
|
|
|
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
|
|
|
|
OpPN->addIncoming(OInst, PN->getIncomingBlock(i));
|
|
|
|
*OI = OpPN;
|
|
|
|
}
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2014-02-11 12:52:27 +00:00
|
|
|
PN->replaceAllUsesWith(New);
|
|
|
|
PN->eraseFromParent();
|
2003-12-10 06:41:05 +00:00
|
|
|
}
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2010-08-29 18:00:00 +00:00
|
|
|
CurAST->deleteValue(&I);
|
2014-02-11 12:52:27 +00:00
|
|
|
I.eraseFromParent();
|
2003-12-10 06:41:05 +00:00
|
|
|
}
|
2002-09-29 21:46:09 +00:00
|
|
|
|
2002-09-26 16:52:07 +00:00
|
|
|
/// hoist - When an instruction is found to only use loop invariant operands
|
|
|
|
/// that is safe to hoist, this instruction is called to do the dirty work.
|
|
|
|
///
|
2003-12-10 06:41:05 +00:00
|
|
|
void LICM::hoist(Instruction &I) {
|
2010-01-05 01:27:30 +00:00
|
|
|
DEBUG(dbgs() << "LICM hoisting to " << Preheader->getName() << ": "
|
2009-10-12 22:25:23 +00:00
|
|
|
<< I << "\n");
|
2003-12-09 19:32:44 +00:00
|
|
|
|
2010-08-29 18:18:40 +00:00
|
|
|
// Move the new node to the Preheader, before its terminator.
|
|
|
|
I.moveBefore(Preheader->getTerminator());
|
2005-04-21 23:48:37 +00:00
|
|
|
|
2003-12-10 06:41:05 +00:00
|
|
|
if (isa<LoadInst>(I)) ++NumMovedLoads;
|
2004-03-15 04:11:30 +00:00
|
|
|
else if (isa<CallInst>(I)) ++NumMovedCalls;
|
2002-09-26 16:38:03 +00:00
|
|
|
++NumHoisted;
|
2002-05-10 22:44:58 +00:00
|
|
|
Changed = true;
|
|
|
|
}
|
|
|
|
|
2003-12-10 06:41:05 +00:00
|
|
|
/// isSafeToExecuteUnconditionally - Only sink or hoist an instruction if it is
|
|
|
|
/// not a trapping instruction or if it is a trapping instruction and is
|
|
|
|
/// guaranteed to execute.
|
2003-08-05 18:45:46 +00:00
|
|
|
///
|
2003-12-10 06:41:05 +00:00
|
|
|
bool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) {
|
2003-12-09 17:18:00 +00:00
|
|
|
// If it is not a trapping instruction, it is always safe to hoist.
|
2011-12-14 23:49:11 +00:00
|
|
|
if (isSafeToSpeculativelyExecute(&Inst))
|
2009-07-17 04:28:42 +00:00
|
|
|
return true;
|
2005-04-21 23:48:37 +00:00
|
|
|
|
2011-07-20 21:37:47 +00:00
|
|
|
return isGuaranteedToExecute(Inst);
|
|
|
|
}
|
|
|
|
|
|
|
|
bool LICM::isGuaranteedToExecute(Instruction &Inst) {
|
2012-09-04 10:25:04 +00:00
|
|
|
|
|
|
|
// Somewhere in this loop there is an instruction which may throw and make us
|
|
|
|
// exit the loop.
|
|
|
|
if (MayThrow)
|
|
|
|
return false;
|
|
|
|
|
2003-12-09 17:18:00 +00:00
|
|
|
// Otherwise we have to check to make sure that the instruction dominates all
|
|
|
|
// of the exit blocks. If it doesn't, then there is a path out of the loop
|
|
|
|
// which does not execute this instruction, so we can't hoist it.
|
|
|
|
|
|
|
|
// If the instruction is in the header block for the loop (which is very
|
|
|
|
// common), it is always guaranteed to dominate the exit blocks. Since this
|
|
|
|
// is a common case, and can save some work, check it now.
|
2003-12-10 06:41:05 +00:00
|
|
|
if (Inst.getParent() == CurLoop->getHeader())
|
2003-12-09 17:18:00 +00:00
|
|
|
return true;
|
|
|
|
|
|
|
|
// Get the exit blocks for the current loop.
|
2007-08-21 00:31:24 +00:00
|
|
|
SmallVector<BasicBlock*, 8> ExitBlocks;
|
2004-04-18 22:15:13 +00:00
|
|
|
CurLoop->getExitBlocks(ExitBlocks);
|
2003-08-05 18:45:46 +00:00
|
|
|
|
2011-01-02 18:45:39 +00:00
|
|
|
// Verify that the block dominates each of the exit blocks of the loop.
|
2003-12-10 06:41:05 +00:00
|
|
|
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
|
2011-01-02 18:45:39 +00:00
|
|
|
if (!DT->dominates(Inst.getParent(), ExitBlocks[i]))
|
2003-12-10 06:41:05 +00:00
|
|
|
return false;
|
2005-04-21 23:48:37 +00:00
|
|
|
|
2012-05-01 04:03:01 +00:00
|
|
|
// As a degenerate case, if the loop is statically infinite then we haven't
|
|
|
|
// proven anything since there are no exit blocks.
|
|
|
|
if (ExitBlocks.empty())
|
|
|
|
return false;
|
|
|
|
|
2003-08-05 18:45:46 +00:00
|
|
|
return true;
|
|
|
|
}
|
|
|
|
|
2011-01-15 00:12:35 +00:00
|
|
|
namespace {
|
|
|
|
class LoopPromoter : public LoadAndStorePromoter {
|
|
|
|
Value *SomePtr; // Designated pointer to store to.
|
|
|
|
SmallPtrSet<Value*, 4> &PointerMustAliases;
|
|
|
|
SmallVectorImpl<BasicBlock*> &LoopExitBlocks;
|
2012-08-08 00:00:26 +00:00
|
|
|
SmallVectorImpl<Instruction*> &LoopInsertPts;
|
2014-02-11 12:52:27 +00:00
|
|
|
PredIteratorCache &PredCache;
|
2011-01-15 00:12:35 +00:00
|
|
|
AliasSetTracker &AST;
|
2014-02-11 12:52:27 +00:00
|
|
|
LoopInfo &LI;
|
2011-05-27 20:31:51 +00:00
|
|
|
DebugLoc DL;
|
2011-07-06 19:19:55 +00:00
|
|
|
int Alignment;
|
2012-12-31 08:37:17 +00:00
|
|
|
MDNode *TBAATag;
|
2014-02-11 12:52:27 +00:00
|
|
|
|
|
|
|
Value *maybeInsertLCSSAPHI(Value *V, BasicBlock *BB) const {
|
|
|
|
if (Instruction *I = dyn_cast<Instruction>(V))
|
|
|
|
if (Loop *L = LI.getLoopFor(I->getParent()))
|
|
|
|
if (!L->contains(BB)) {
|
|
|
|
// We need to create an LCSSA PHI node for the incoming value and
|
|
|
|
// store that.
|
|
|
|
PHINode *PN = PHINode::Create(
|
|
|
|
I->getType(), PredCache.GetNumPreds(BB),
|
|
|
|
I->getName() + ".lcssa", BB->begin());
|
|
|
|
for (BasicBlock **PI = PredCache.GetPreds(BB); *PI; ++PI)
|
|
|
|
PN->addIncoming(I, *PI);
|
|
|
|
return PN;
|
|
|
|
}
|
|
|
|
return V;
|
|
|
|
}
|
|
|
|
|
2011-01-15 00:12:35 +00:00
|
|
|
public:
|
2014-02-11 12:52:27 +00:00
|
|
|
LoopPromoter(Value *SP, const SmallVectorImpl<Instruction *> &Insts,
|
|
|
|
SSAUpdater &S, SmallPtrSet<Value *, 4> &PMA,
|
|
|
|
SmallVectorImpl<BasicBlock *> &LEB,
|
|
|
|
SmallVectorImpl<Instruction *> &LIP, PredIteratorCache &PIC,
|
|
|
|
AliasSetTracker &ast, LoopInfo &li, DebugLoc dl, int alignment,
|
2012-12-31 08:37:17 +00:00
|
|
|
MDNode *TBAATag)
|
2014-02-11 12:52:27 +00:00
|
|
|
: LoadAndStorePromoter(Insts, S), SomePtr(SP), PointerMustAliases(PMA),
|
|
|
|
LoopExitBlocks(LEB), LoopInsertPts(LIP), PredCache(PIC), AST(ast),
|
|
|
|
LI(li), DL(dl), Alignment(alignment), TBAATag(TBAATag) {}
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2014-03-05 09:10:37 +00:00
|
|
|
bool isInstInList(Instruction *I,
|
|
|
|
const SmallVectorImpl<Instruction*> &) const override {
|
2011-01-15 00:12:35 +00:00
|
|
|
Value *Ptr;
|
|
|
|
if (LoadInst *LI = dyn_cast<LoadInst>(I))
|
|
|
|
Ptr = LI->getOperand(0);
|
|
|
|
else
|
|
|
|
Ptr = cast<StoreInst>(I)->getPointerOperand();
|
|
|
|
return PointerMustAliases.count(Ptr);
|
|
|
|
}
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2014-03-05 09:10:37 +00:00
|
|
|
void doExtraRewritesBeforeFinalDeletion() const override {
|
2011-01-15 00:12:35 +00:00
|
|
|
// Insert stores after in the loop exit blocks. Each exit block gets a
|
|
|
|
// store of the live-out values that feed them. Since we've already told
|
|
|
|
// the SSA updater about the defs in the loop and the preheader
|
|
|
|
// definition, it is all set and we can start using it.
|
|
|
|
for (unsigned i = 0, e = LoopExitBlocks.size(); i != e; ++i) {
|
|
|
|
BasicBlock *ExitBlock = LoopExitBlocks[i];
|
|
|
|
Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock);
|
2014-02-11 12:52:27 +00:00
|
|
|
LiveInValue = maybeInsertLCSSAPHI(LiveInValue, ExitBlock);
|
|
|
|
Value *Ptr = maybeInsertLCSSAPHI(SomePtr, ExitBlock);
|
2012-08-08 00:00:26 +00:00
|
|
|
Instruction *InsertPos = LoopInsertPts[i];
|
2014-02-11 12:52:27 +00:00
|
|
|
StoreInst *NewSI = new StoreInst(LiveInValue, Ptr, InsertPos);
|
2011-07-06 19:19:55 +00:00
|
|
|
NewSI->setAlignment(Alignment);
|
2011-05-27 20:31:51 +00:00
|
|
|
NewSI->setDebugLoc(DL);
|
2012-12-31 08:37:17 +00:00
|
|
|
if (TBAATag) NewSI->setMetadata(LLVMContext::MD_tbaa, TBAATag);
|
2011-01-15 00:12:35 +00:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2014-03-05 09:10:37 +00:00
|
|
|
void replaceLoadWithValue(LoadInst *LI, Value *V) const override {
|
2011-01-15 00:12:35 +00:00
|
|
|
// Update alias analysis.
|
|
|
|
AST.copyValue(LI, V);
|
|
|
|
}
|
2014-03-05 09:10:37 +00:00
|
|
|
void instructionDeleted(Instruction *I) const override {
|
2011-01-15 00:12:35 +00:00
|
|
|
AST.deleteValue(I);
|
|
|
|
}
|
|
|
|
};
|
|
|
|
} // end anon namespace
|
|
|
|
|
2010-08-29 06:43:52 +00:00
|
|
|
/// PromoteAliasSet - Try to promote memory values to scalars by sinking
|
2003-02-24 03:52:32 +00:00
|
|
|
/// stores out of the loop and moving loads to before the loop. We do this by
|
|
|
|
/// looping over the stores in the loop, looking for stores to Must pointers
|
2010-08-29 06:43:52 +00:00
|
|
|
/// which are loop invariant.
|
2003-02-24 03:52:32 +00:00
|
|
|
///
|
2012-08-08 00:00:26 +00:00
|
|
|
void LICM::PromoteAliasSet(AliasSet &AS,
|
|
|
|
SmallVectorImpl<BasicBlock*> &ExitBlocks,
|
2014-02-11 12:52:27 +00:00
|
|
|
SmallVectorImpl<Instruction*> &InsertPts,
|
|
|
|
PredIteratorCache &PIC) {
|
2010-08-29 06:43:52 +00:00
|
|
|
// We can promote this alias set if it has a store, if it is a "Must" alias
|
|
|
|
// set, if the pointer is loop invariant, and if we are not eliminating any
|
|
|
|
// volatile loads or stores.
|
|
|
|
if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() ||
|
|
|
|
AS.isVolatile() || !CurLoop->isLoopInvariant(AS.begin()->getValue()))
|
|
|
|
return;
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2010-08-29 06:43:52 +00:00
|
|
|
assert(!AS.empty() &&
|
|
|
|
"Must alias set should have at least one pointer element in it!");
|
|
|
|
Value *SomePtr = AS.begin()->getValue();
|
2005-04-21 23:48:37 +00:00
|
|
|
|
2010-08-29 06:43:52 +00:00
|
|
|
// It isn't safe to promote a load/store from the loop if the load/store is
|
|
|
|
// conditional. For example, turning:
|
2003-02-24 03:52:32 +00:00
|
|
|
//
|
2010-08-29 06:43:52 +00:00
|
|
|
// for () { if (c) *P += 1; }
|
2003-02-24 03:52:32 +00:00
|
|
|
//
|
2010-08-29 06:43:52 +00:00
|
|
|
// into:
|
|
|
|
//
|
|
|
|
// tmp = *P; for () { if (c) tmp +=1; } *P = tmp;
|
|
|
|
//
|
|
|
|
// is not safe, because *P may only be valid to access if 'c' is true.
|
2011-07-06 19:20:02 +00:00
|
|
|
//
|
2010-08-29 06:43:52 +00:00
|
|
|
// It is safe to promote P if all uses are direct load/stores and if at
|
|
|
|
// least one is guaranteed to be executed.
|
|
|
|
bool GuaranteedToExecute = false;
|
2011-07-06 19:19:55 +00:00
|
|
|
|
2010-08-29 06:43:52 +00:00
|
|
|
SmallVector<Instruction*, 64> LoopUses;
|
|
|
|
SmallPtrSet<Value*, 4> PointerMustAliases;
|
|
|
|
|
2011-07-06 19:19:55 +00:00
|
|
|
// We start with an alignment of one and try to find instructions that allow
|
|
|
|
// us to prove better alignment.
|
|
|
|
unsigned Alignment = 1;
|
2012-12-31 08:37:17 +00:00
|
|
|
MDNode *TBAATag = 0;
|
2011-07-06 19:19:55 +00:00
|
|
|
|
2010-08-29 06:43:52 +00:00
|
|
|
// Check that all of the pointers in the alias set have the same type. We
|
|
|
|
// cannot (yet) promote a memory location that is loaded and stored in
|
2012-12-31 08:37:17 +00:00
|
|
|
// different sizes. While we are at it, collect alignment and TBAA info.
|
2010-08-29 06:43:52 +00:00
|
|
|
for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) {
|
|
|
|
Value *ASIV = ASI->getValue();
|
|
|
|
PointerMustAliases.insert(ASIV);
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2008-05-22 00:53:38 +00:00
|
|
|
// Check that all of the pointers in the alias set have the same type. We
|
|
|
|
// cannot (yet) promote a memory location that is loaded and stored in
|
|
|
|
// different sizes.
|
2010-08-29 06:43:52 +00:00
|
|
|
if (SomePtr->getType() != ASIV->getType())
|
|
|
|
return;
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2014-03-09 03:16:01 +00:00
|
|
|
for (User *U : ASIV->users()) {
|
2010-08-29 06:43:52 +00:00
|
|
|
// Ignore instructions that are outside the loop.
|
2014-03-09 03:16:01 +00:00
|
|
|
Instruction *UI = dyn_cast<Instruction>(U);
|
|
|
|
if (!UI || !CurLoop->contains(UI))
|
2008-05-22 00:53:38 +00:00
|
|
|
continue;
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2010-08-29 06:43:52 +00:00
|
|
|
// If there is an non-load/store instruction in the loop, we can't promote
|
|
|
|
// it.
|
2014-03-09 03:16:01 +00:00
|
|
|
if (LoadInst *load = dyn_cast<LoadInst>(UI)) {
|
2011-08-15 20:52:09 +00:00
|
|
|
assert(!load->isVolatile() && "AST broken");
|
|
|
|
if (!load->isSimple())
|
|
|
|
return;
|
2014-03-09 03:16:01 +00:00
|
|
|
} else if (StoreInst *store = dyn_cast<StoreInst>(UI)) {
|
2010-12-19 05:57:25 +00:00
|
|
|
// Stores *of* the pointer are not interesting, only stores *to* the
|
|
|
|
// pointer.
|
2014-03-09 03:16:01 +00:00
|
|
|
if (UI->getOperand(1) != ASIV)
|
2010-12-19 05:57:25 +00:00
|
|
|
continue;
|
2011-08-15 20:52:09 +00:00
|
|
|
assert(!store->isVolatile() && "AST broken");
|
|
|
|
if (!store->isSimple())
|
|
|
|
return;
|
2011-07-06 19:19:55 +00:00
|
|
|
|
2011-07-20 21:37:47 +00:00
|
|
|
// Note that we only check GuaranteedToExecute inside the store case
|
|
|
|
// so that we do not introduce stores where they did not exist before
|
|
|
|
// (which would break the LLVM concurrency model).
|
|
|
|
|
|
|
|
// If the alignment of this instruction allows us to specify a more
|
|
|
|
// restrictive (and performant) alignment and if we are sure this
|
|
|
|
// instruction will be executed, update the alignment.
|
|
|
|
// Larger is better, with the exception of 0 being the best alignment.
|
2011-08-15 20:52:09 +00:00
|
|
|
unsigned InstAlignment = store->getAlignment();
|
2012-12-31 08:37:17 +00:00
|
|
|
if ((InstAlignment > Alignment || InstAlignment == 0) && Alignment != 0)
|
2014-03-09 03:16:01 +00:00
|
|
|
if (isGuaranteedToExecute(*UI)) {
|
2011-07-20 21:37:47 +00:00
|
|
|
GuaranteedToExecute = true;
|
|
|
|
Alignment = InstAlignment;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (!GuaranteedToExecute)
|
2014-03-09 03:16:01 +00:00
|
|
|
GuaranteedToExecute = isGuaranteedToExecute(*UI);
|
2011-07-06 19:19:55 +00:00
|
|
|
|
2011-07-20 21:37:47 +00:00
|
|
|
} else
|
|
|
|
return; // Not a load or store.
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2012-12-31 08:37:17 +00:00
|
|
|
// Merge the TBAA tags.
|
|
|
|
if (LoopUses.empty()) {
|
|
|
|
// On the first load/store, just take its TBAA tag.
|
2014-03-09 03:16:01 +00:00
|
|
|
TBAATag = UI->getMetadata(LLVMContext::MD_tbaa);
|
2013-01-05 16:44:07 +00:00
|
|
|
} else if (TBAATag) {
|
|
|
|
TBAATag = MDNode::getMostGenericTBAA(TBAATag,
|
2014-03-09 03:16:01 +00:00
|
|
|
UI->getMetadata(LLVMContext::MD_tbaa));
|
2012-12-31 08:37:17 +00:00
|
|
|
}
|
2014-03-09 03:16:01 +00:00
|
|
|
|
|
|
|
LoopUses.push_back(UI);
|
2008-05-22 00:53:38 +00:00
|
|
|
}
|
2010-08-29 06:43:52 +00:00
|
|
|
}
|
2011-07-06 19:19:55 +00:00
|
|
|
|
2010-08-29 06:43:52 +00:00
|
|
|
// If there isn't a guaranteed-to-execute instruction, we can't promote.
|
|
|
|
if (!GuaranteedToExecute)
|
|
|
|
return;
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2010-08-29 06:43:52 +00:00
|
|
|
// Otherwise, this is safe to promote, lets do it!
|
2011-07-06 19:20:02 +00:00
|
|
|
DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " <<*SomePtr<<'\n');
|
2010-08-29 06:43:52 +00:00
|
|
|
Changed = true;
|
|
|
|
++NumPromoted;
|
2007-10-01 18:12:58 +00:00
|
|
|
|
2011-05-27 20:31:51 +00:00
|
|
|
// Grab a debug location for the inserted loads/stores; given that the
|
|
|
|
// inserted loads/stores have little relation to the original loads/stores,
|
|
|
|
// this code just arbitrarily picks a location from one, since any debug
|
|
|
|
// location is better than none.
|
|
|
|
DebugLoc DL = LoopUses[0]->getDebugLoc();
|
|
|
|
|
2012-08-08 00:00:26 +00:00
|
|
|
// Figure out the loop exits and their insertion points, if this is the
|
|
|
|
// first promotion.
|
|
|
|
if (ExitBlocks.empty()) {
|
|
|
|
CurLoop->getUniqueExitBlocks(ExitBlocks);
|
|
|
|
InsertPts.resize(ExitBlocks.size());
|
|
|
|
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i)
|
|
|
|
InsertPts[i] = ExitBlocks[i]->getFirstInsertionPt();
|
|
|
|
}
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2010-08-29 06:43:52 +00:00
|
|
|
// We use the SSAUpdater interface to insert phi nodes as required.
|
|
|
|
SmallVector<PHINode*, 16> NewPHIs;
|
|
|
|
SSAUpdater SSA(&NewPHIs);
|
2011-01-15 00:12:35 +00:00
|
|
|
LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks,
|
2014-02-11 12:52:27 +00:00
|
|
|
InsertPts, PIC, *CurAST, *LI, DL, Alignment, TBAATag);
|
2011-07-06 19:20:02 +00:00
|
|
|
|
2011-01-15 00:12:35 +00:00
|
|
|
// Set up the preheader to have a definition of the value. It is the live-out
|
|
|
|
// value from the preheader that uses in the loop will use.
|
|
|
|
LoadInst *PreheaderLoad =
|
|
|
|
new LoadInst(SomePtr, SomePtr->getName()+".promoted",
|
|
|
|
Preheader->getTerminator());
|
2011-07-06 19:19:55 +00:00
|
|
|
PreheaderLoad->setAlignment(Alignment);
|
2011-05-27 20:31:51 +00:00
|
|
|
PreheaderLoad->setDebugLoc(DL);
|
2012-12-31 08:37:17 +00:00
|
|
|
if (TBAATag) PreheaderLoad->setMetadata(LLVMContext::MD_tbaa, TBAATag);
|
2010-08-29 06:43:52 +00:00
|
|
|
SSA.AddAvailableValue(Preheader, PreheaderLoad);
|
|
|
|
|
2011-01-15 00:12:35 +00:00
|
|
|
// Rewrite all the loads in the loop and remember all the definitions from
|
|
|
|
// stores in the loop.
|
|
|
|
Promoter.run(LoopUses);
|
2011-04-07 01:35:06 +00:00
|
|
|
|
|
|
|
// If the SSAUpdater didn't use the load in the preheader, just zap it now.
|
|
|
|
if (PreheaderLoad->use_empty())
|
|
|
|
PreheaderLoad->eraseFromParent();
|
2002-08-22 21:39:55 +00:00
|
|
|
}
|
2007-07-31 08:01:41 +00:00
|
|
|
|
2010-08-29 06:43:52 +00:00
|
|
|
|
2007-07-31 08:01:41 +00:00
|
|
|
/// cloneBasicBlockAnalysis - Simple Analysis hook. Clone alias set info.
|
|
|
|
void LICM::cloneBasicBlockAnalysis(BasicBlock *From, BasicBlock *To, Loop *L) {
|
2010-08-29 17:46:00 +00:00
|
|
|
AliasSetTracker *AST = LoopToAliasSetMap.lookup(L);
|
2007-07-31 08:01:41 +00:00
|
|
|
if (!AST)
|
|
|
|
return;
|
|
|
|
|
|
|
|
AST->copyValue(From, To);
|
|
|
|
}
|
|
|
|
|
|
|
|
/// deleteAnalysisValue - Simple Analysis hook. Delete value V from alias
|
|
|
|
/// set.
|
|
|
|
void LICM::deleteAnalysisValue(Value *V, Loop *L) {
|
2010-08-29 17:46:00 +00:00
|
|
|
AliasSetTracker *AST = LoopToAliasSetMap.lookup(L);
|
2007-07-31 08:01:41 +00:00
|
|
|
if (!AST)
|
|
|
|
return;
|
|
|
|
|
|
|
|
AST->deleteValue(V);
|
|
|
|
}
|