67 lines · cpp
1//===- StripGCRelocates.cpp - Remove gc.relocates inserted by RewriteStatePoints===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This is a little utility pass that removes the gc.relocates inserted by10// RewriteStatepointsForGC. Note that the generated IR is incorrect,11// but this is useful as a single pass in itself, for analysis of IR, without12// the GC.relocates. The statepoint and gc.result intrinsics would still be13// present.14//===----------------------------------------------------------------------===//15 16#include "llvm/Transforms/Utils/StripGCRelocates.h"17#include "llvm/IR/Function.h"18#include "llvm/IR/InstIterator.h"19#include "llvm/IR/Instructions.h"20#include "llvm/IR/Statepoint.h"21 22using namespace llvm;23 24static bool stripGCRelocates(Function &F) {25 // Nothing to do for declarations.26 if (F.isDeclaration())27 return false;28 SmallVector<GCRelocateInst *, 20> GCRelocates;29 // TODO: We currently do not handle gc.relocates that are in landing pads,30 // i.e. not bound to a single statepoint token.31 for (Instruction &I : instructions(F)) {32 if (auto *GCR = dyn_cast<GCRelocateInst>(&I))33 if (isa<GCStatepointInst>(GCR->getOperand(0)))34 GCRelocates.push_back(GCR);35 }36 // All gc.relocates are bound to a single statepoint token. The order of37 // visiting gc.relocates for deletion does not matter.38 for (GCRelocateInst *GCRel : GCRelocates) {39 Value *OrigPtr = GCRel->getDerivedPtr();40 Value *ReplaceGCRel = OrigPtr;41 42 // All gc_relocates are i8 addrspace(1)* typed, we need a bitcast from i843 // addrspace(1)* to the type of the OrigPtr, if the are not the same.44 if (GCRel->getType() != OrigPtr->getType())45 ReplaceGCRel = new BitCastInst(OrigPtr, GCRel->getType(), "cast", GCRel->getIterator());46 47 // Replace all uses of gc.relocate and delete the gc.relocate48 // There maybe unncessary bitcasts back to the OrigPtr type, an instcombine49 // pass would clear this up.50 GCRel->replaceAllUsesWith(ReplaceGCRel);51 GCRel->eraseFromParent();52 }53 return !GCRelocates.empty();54}55 56PreservedAnalyses StripGCRelocates::run(Function &F,57 FunctionAnalysisManager &AM) {58 if (!stripGCRelocates(F))59 return PreservedAnalyses::all();60 61 // Removing gc.relocate preserves the CFG, but most other analysis probably62 // need to re-run.63 PreservedAnalyses PA;64 PA.preserveSet<CFGAnalyses>();65 return PA;66}67