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author | Chris Lattner <sabre@nondot.org> | 2003-12-09 19:32:44 +0000 |
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committer | Chris Lattner <sabre@nondot.org> | 2003-12-09 19:32:44 +0000 |
commit | ed6dfc2856cd44a8aa608a9074eabbf42dd6cadc (patch) | |
tree | f48406d274b4c4460b40bb57362523d9f04c86ce /lib/Transforms/Scalar | |
parent | 92094b4d928119eceac1484331acffe950f4651c (diff) | |
download | external_llvm-ed6dfc2856cd44a8aa608a9074eabbf42dd6cadc.zip external_llvm-ed6dfc2856cd44a8aa608a9074eabbf42dd6cadc.tar.gz external_llvm-ed6dfc2856cd44a8aa608a9074eabbf42dd6cadc.tar.bz2 |
Refactor code a little bit, eliminating the gratuitous InstVisitor, which
should make subsequent changes simpler. This also allows us to hoist vaarg
and vanext instructions
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10342 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms/Scalar')
-rw-r--r-- | lib/Transforms/Scalar/LICM.cpp | 84 |
1 files changed, 43 insertions, 41 deletions
diff --git a/lib/Transforms/Scalar/LICM.cpp b/lib/Transforms/Scalar/LICM.cpp index 7ac318a..2a8dc7c 100644 --- a/lib/Transforms/Scalar/LICM.cpp +++ b/lib/Transforms/Scalar/LICM.cpp @@ -41,7 +41,6 @@ #include "llvm/Instructions.h" #include "llvm/DerivedTypes.h" #include "llvm/Target/TargetData.h" -#include "llvm/Support/InstVisitor.h" #include "llvm/Support/CFG.h" #include "Support/CommandLine.h" #include "Support/Debug.h" @@ -60,7 +59,7 @@ namespace { Statistic<> NumPromoted("licm", "Number of memory locations promoted to registers"); - struct LICM : public FunctionPass, public InstVisitor<LICM> { + struct LICM : public FunctionPass { virtual bool runOnFunction(Function &F); /// This transformation requires natural loop information & requires that @@ -137,6 +136,7 @@ namespace { return !CurLoop->contains(I->getParent()); return true; // All non-instructions are loop invariant } + bool isLoopInvariantInst(Instruction &Inst); /// PromoteValuesInLoop - Look at the stores in the loop and promote as many /// to scalars as we can. @@ -152,32 +152,6 @@ namespace { void findPromotableValuesInLoop( std::vector<std::pair<AllocaInst*, Value*> > &PromotedValues, std::map<Value*, AllocaInst*> &Val2AlMap); - - - /// Instruction visitation handlers... these basically control whether or - /// not the specified instruction types are hoisted. - /// - friend class InstVisitor<LICM>; - void visitBinaryOperator(Instruction &I) { - if (isLoopInvariant(I.getOperand(0)) && - isLoopInvariant(I.getOperand(1)) && SafeToHoist(I)) - hoist(I); - } - void visitCastInst(CastInst &CI) { - Instruction &I = (Instruction&)CI; - if (isLoopInvariant(I.getOperand(0)) && SafeToHoist(CI)) hoist(I); - } - void visitShiftInst(ShiftInst &I) { visitBinaryOperator((Instruction&)I); } - - void visitLoadInst(LoadInst &LI); - - void visitGetElementPtrInst(GetElementPtrInst &GEPI) { - Instruction &I = (Instruction&)GEPI; - for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) - if (!isLoopInvariant(I.getOperand(i))) return; - if(SafeToHoist(GEPI)) - hoist(I); - } }; RegisterOpt<LICM> X("licm", "Loop Invariant Code Motion"); @@ -202,7 +176,7 @@ bool LICM::runOnFunction(Function &) { for (std::vector<Loop*>::const_iterator I = TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) { AliasSetTracker AST(*AA); - LICM::visitLoop(*I, AST); + visitLoop(*I, AST); } return Changed; } @@ -215,7 +189,7 @@ void LICM::visitLoop(Loop *L, AliasSetTracker &AST) { for (std::vector<Loop*>::const_iterator I = L->getSubLoops().begin(), E = L->getSubLoops().end(); I != E; ++I) { AliasSetTracker SubAST(*AA); - LICM::visitLoop(*I, SubAST); + visitLoop(*I, SubAST); // Incorporate information about the subloops into this loop... AST.add(SubAST); @@ -265,20 +239,53 @@ void LICM::visitLoop(Loop *L, AliasSetTracker &AST) { /// void LICM::HoistRegion(DominatorTree::Node *N) { assert(N != 0 && "Null dominator tree node?"); + BasicBlock *BB = N->getBlock(); // If this subregion is not in the top level loop at all, exit. - if (!CurLoop->contains(N->getBlock())) return; + if (!CurLoop->contains(BB)) return; // Only need to hoist the contents of this block if it is not part of a // subloop (which would already have been hoisted) - if (!inSubLoop(N->getBlock())) - visit(*N->getBlock()); + if (!inSubLoop(BB)) + for (BasicBlock::iterator I = BB->begin(), E = --BB->end(); I != E; ) { + Instruction &Inst = *I++; + if (isLoopInvariantInst(Inst) && SafeToHoist(Inst)) + hoist(Inst); + } const std::vector<DominatorTree::Node*> &Children = N->getChildren(); for (unsigned i = 0, e = Children.size(); i != e; ++i) HoistRegion(Children[i]); } +bool LICM::isLoopInvariantInst(Instruction &I) { + assert(!isa<TerminatorInst>(I) && "Can't hoist terminator instructions!"); + + // We can only hoist simple expressions... + if (!isa<BinaryOperator>(I) && !isa<ShiftInst>(I) && !isa<LoadInst>(I) && + !isa<GetElementPtrInst>(I) && !isa<CastInst>(I) && !isa<VANextInst>(I) && + !isa<VAArgInst>(I)) + return false; + + // The instruction is loop invariant if all of its operands are loop-invariant + for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i) + if (!isLoopInvariant(I.getOperand(i))) + return false; + + // Loads have extra constraints we have to verify before we can hoist them. + if (LoadInst *LI = dyn_cast<LoadInst>(&I)) { + if (LI->isVolatile()) + return false; // Don't hoist volatile loads! + + // Don't hoist loads which have may-aliased stores in loop. + if (pointerInvalidatedByLoop(I.getOperand(0))) + return false; + } + + // If we got this far, the instruction is loop invariant! + return true; +} + /// 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. @@ -288,6 +295,9 @@ void LICM::hoist(Instruction &Inst) { WriteAsOperand(std::cerr, Preheader, false); std::cerr << ": " << Inst); + if (isa<LoadInst>(Inst)) + ++NumHoistedLoads; + // Remove the instruction from its current basic block... but don't delete the // instruction. Inst.getParent()->getInstList().remove(&Inst); @@ -344,14 +354,6 @@ bool LICM::SafeToHoist(Instruction &Inst) { } -void LICM::visitLoadInst(LoadInst &LI) { - if (isLoopInvariant(LI.getOperand(0)) && !LI.isVolatile() && - !pointerInvalidatedByLoop(LI.getOperand(0)) && SafeToHoist(LI)) { - hoist(LI); - ++NumHoistedLoads; - } -} - /// PromoteValuesInLoop - Try to promote memory values to scalars by sinking /// 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 |