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99 lines
3.1 KiB
C++
99 lines
3.1 KiB
C++
//===------ RewriteByReferenceParameters.cpp --------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass introduces separate 'alloca' instructions for read-only
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// by-reference function parameters to indicate that these paramters are
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// read-only. After this transformation -mem2reg has more freedom to promote
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// variables to registers, which allows SCEV to work in more cases.
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//
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//===----------------------------------------------------------------------===//
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#include "polly/LinkAllPasses.h"
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#include "llvm/IR/Instruction.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/Pass.h"
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#define DEBUG_TYPE "polly-rewrite-byref-params"
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using namespace llvm;
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namespace {
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class RewriteByrefParams : public FunctionPass {
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private:
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RewriteByrefParams(const RewriteByrefParams &) = delete;
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const RewriteByrefParams &operator=(const RewriteByrefParams &) = delete;
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public:
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static char ID;
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explicit RewriteByrefParams() : FunctionPass(ID) {}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const override {}
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void tryRewriteInstruction(Instruction &Inst) {
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BasicBlock *Entry = &Inst.getParent()->getParent()->getEntryBlock();
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auto *Call = dyn_cast<CallInst>(&Inst);
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if (!Call)
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return;
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llvm::Function *F = Call->getCalledFunction();
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if (!F)
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return;
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// We currently match for a very specific function. In case this proves
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// useful, we can make this code dependent on readonly metadata.
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if (!F->hasName() || F->getName() != "_gfortran_transfer_integer_write")
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return;
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auto *BitCast = dyn_cast<BitCastInst>(Call->getOperand(1));
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if (!BitCast)
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return;
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auto *Alloca = dyn_cast<AllocaInst>(BitCast->getOperand(0));
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if (!Alloca)
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return;
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std::string InstName = Alloca->getName().str();
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auto NewAlloca =
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new AllocaInst(Alloca->getAllocatedType(), 0,
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"polly_byref_alloca_" + InstName, &*Entry->begin());
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auto *LoadedVal = new LoadInst(Alloca->getAllocatedType(), Alloca,
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"polly_byref_load_" + InstName, &Inst);
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new StoreInst(LoadedVal, NewAlloca, &Inst);
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auto *NewBitCast = new BitCastInst(NewAlloca, BitCast->getType(),
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"polly_byref_cast_" + InstName, &Inst);
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Call->setOperand(1, NewBitCast);
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}
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virtual bool runOnFunction(Function &F) override {
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for (BasicBlock &BB : F)
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for (Instruction &Inst : BB)
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tryRewriteInstruction(Inst);
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return true;
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}
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};
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char RewriteByrefParams::ID;
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} // anonymous namespace
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Pass *polly::createRewriteByrefParamsPass() { return new RewriteByrefParams(); }
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INITIALIZE_PASS_BEGIN(RewriteByrefParams, "polly-rewrite-byref-params",
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"Polly - Rewrite by reference parameters", false, false)
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INITIALIZE_PASS_END(RewriteByrefParams, "polly-rewrite-byref-params",
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"Polly - Rewrite by reference parameters", false, false)
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