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https://github.com/c64scene-ar/llvm-6502.git
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8a261e44f7
to declare that they preserve other passes without needing to pull in additional header file or library dependencies. Convert MachineFunctionPass and CodeGenLICM to make use of this. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83555 91177308-0d34-0410-b5e6-96231b3b80d8
113 lines
3.8 KiB
C++
113 lines
3.8 KiB
C++
//===- CodeGenLICM.cpp - LICM a function for code generation --------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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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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//
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//===----------------------------------------------------------------------===//
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//
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// This function performs late LICM, hoisting constants out of loops that
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// are not valid immediates. It should not be followed by instcombine,
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// because instcombine would quickly stuff the constants back into the loop.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "codegen-licm"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/Analysis/LoopPass.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/ADT/DenseMap.h"
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using namespace llvm;
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namespace {
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class CodeGenLICM : public LoopPass {
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virtual bool runOnLoop(Loop *L, LPPassManager &LPM);
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virtual void getAnalysisUsage(AnalysisUsage &AU) const;
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public:
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static char ID; // Pass identification, replacement for typeid
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explicit CodeGenLICM() : LoopPass(&ID) {}
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};
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}
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char CodeGenLICM::ID = 0;
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static RegisterPass<CodeGenLICM> X("codegen-licm",
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"hoist constants out of loops");
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Pass *llvm::createCodeGenLICMPass() {
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return new CodeGenLICM();
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}
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bool CodeGenLICM::runOnLoop(Loop *L, LPPassManager &) {
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bool Changed = false;
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// Only visit outermost loops.
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if (L->getParentLoop()) return Changed;
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Instruction *PreheaderTerm = L->getLoopPreheader()->getTerminator();
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DenseMap<Constant *, BitCastInst *> HoistedConstants;
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for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
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I != E; ++I) {
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BasicBlock *BB = *I;
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for (BasicBlock::iterator BBI = BB->begin(), BBE = BB->end();
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BBI != BBE; ++BBI) {
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Instruction *I = BBI;
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// TODO: For now, skip all intrinsic instructions, because some of them
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// can require their operands to be constants, and we don't want to
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// break that.
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if (isa<IntrinsicInst>(I))
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continue;
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// LLVM represents fneg as -0.0-x; don't hoist the -0.0 out.
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if (BinaryOperator::isFNeg(I) ||
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BinaryOperator::isNeg(I) ||
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BinaryOperator::isNot(I))
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continue;
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for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
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// Don't hoist out switch case constants.
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if (isa<SwitchInst>(I) && i == 1)
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break;
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// Don't hoist out shuffle masks.
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if (isa<ShuffleVectorInst>(I) && i == 2)
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break;
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Value *Op = I->getOperand(i);
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Constant *C = dyn_cast<Constant>(Op);
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if (!C) continue;
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// TODO: Ask the target which constants are legal. This would allow
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// us to add support for hoisting ConstantInts and GlobalValues too.
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if (isa<ConstantFP>(C) ||
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isa<ConstantVector>(C) ||
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isa<ConstantAggregateZero>(C)) {
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BitCastInst *&BC = HoistedConstants[C];
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if (!BC)
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BC = new BitCastInst(C, C->getType(), "hoist", PreheaderTerm);
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I->setOperand(i, BC);
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Changed = true;
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}
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}
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}
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}
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return Changed;
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}
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void CodeGenLICM::getAnalysisUsage(AnalysisUsage &AU) const {
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// This pass preserves just about everything. List some popular things here.
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AU.setPreservesCFG();
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AU.addPreservedID(LoopSimplifyID);
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AU.addPreserved<LoopInfo>();
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AU.addPreserved<AliasAnalysis>();
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AU.addPreserved("scalar-evolution");
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AU.addPreserved("iv-users");
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AU.addPreserved("lda");
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AU.addPreserved("live-values");
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// Hoisting requires a loop preheader.
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AU.addRequiredID(LoopSimplifyID);
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}
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