87 lines
3.3 KiB
C++
87 lines
3.3 KiB
C++
//===- StripGCRelocates.cpp - Remove gc.relocates inserted by RewriteStatePoints===//
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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 is a little utility pass that removes the gc.relocates inserted by
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// RewriteStatepointsForGC. Note that the generated IR is incorrect,
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// but this is useful as a single pass in itself, for analysis of IR, without
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// the GC.relocates. The statepoint and gc.result intrinsics would still be
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// present.
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Utils/StripGCRelocates.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/InstIterator.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/IR/Statepoint.h"
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#include "llvm/InitializePasses.h"
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#include "llvm/Pass.h"
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using namespace llvm;
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static bool stripGCRelocates(Function &F) {
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// Nothing to do for declarations.
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if (F.isDeclaration())
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return false;
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SmallVector<GCRelocateInst *, 20> GCRelocates;
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// TODO: We currently do not handle gc.relocates that are in landing pads,
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// i.e. not bound to a single statepoint token.
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for (Instruction &I : instructions(F)) {
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if (auto *GCR = dyn_cast<GCRelocateInst>(&I))
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if (isa<GCStatepointInst>(GCR->getOperand(0)))
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GCRelocates.push_back(GCR);
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}
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// All gc.relocates are bound to a single statepoint token. The order of
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// visiting gc.relocates for deletion does not matter.
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for (GCRelocateInst *GCRel : GCRelocates) {
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Value *OrigPtr = GCRel->getDerivedPtr();
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Value *ReplaceGCRel = OrigPtr;
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// All gc_relocates are i8 addrspace(1)* typed, we need a bitcast from i8
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// addrspace(1)* to the type of the OrigPtr, if the are not the same.
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if (GCRel->getType() != OrigPtr->getType())
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ReplaceGCRel = new BitCastInst(OrigPtr, GCRel->getType(), "cast", GCRel);
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// Replace all uses of gc.relocate and delete the gc.relocate
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// There maybe unncessary bitcasts back to the OrigPtr type, an instcombine
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// pass would clear this up.
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GCRel->replaceAllUsesWith(ReplaceGCRel);
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GCRel->eraseFromParent();
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}
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return !GCRelocates.empty();
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}
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PreservedAnalyses StripGCRelocates::run(Function &F,
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FunctionAnalysisManager &AM) {
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if (!stripGCRelocates(F))
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return PreservedAnalyses::all();
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// Removing gc.relocate preserves the CFG, but most other analysis probably
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// need to re-run.
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PreservedAnalyses PA;
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PA.preserveSet<CFGAnalyses>();
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return PA;
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}
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namespace {
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struct StripGCRelocatesLegacy : public FunctionPass {
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static char ID; // Pass identification, replacement for typeid
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StripGCRelocatesLegacy() : FunctionPass(ID) {
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initializeStripGCRelocatesLegacyPass(*PassRegistry::getPassRegistry());
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}
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void getAnalysisUsage(AnalysisUsage &Info) const override {}
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bool runOnFunction(Function &F) override { return ::stripGCRelocates(F); }
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};
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char StripGCRelocatesLegacy::ID = 0;
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} // namespace
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INITIALIZE_PASS(StripGCRelocatesLegacy, "strip-gc-relocates",
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"Strip gc.relocates inserted through RewriteStatepointsForGC",
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true, false)
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