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-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This is a little utility pass that removes the gc.relocates inserted by 10 // RewriteStatepointsForGC. Note that the generated IR is incorrect, 11 // but this is useful as a single pass in itself, for analysis of IR, without 12 // the GC.relocates. The statepoint and gc.result instrinsics would still be 13 // present. 14 //===----------------------------------------------------------------------===// 15 16 #include "llvm/IR/Function.h" 17 #include "llvm/IR/InstIterator.h" 18 #include "llvm/IR/Instructions.h" 19 #include "llvm/IR/Statepoint.h" 20 #include "llvm/IR/Type.h" 21 #include "llvm/InitializePasses.h" 22 #include "llvm/Pass.h" 23 #include "llvm/Support/raw_ostream.h" 24 25 using namespace llvm; 26 27 namespace { 28 struct StripGCRelocates : public FunctionPass { 29 static char ID; // Pass identification, replacement for typeid 30 StripGCRelocates() : FunctionPass(ID) { 31 initializeStripGCRelocatesPass(*PassRegistry::getPassRegistry()); 32 } 33 34 void getAnalysisUsage(AnalysisUsage &Info) const override {} 35 36 bool runOnFunction(Function &F) override; 37 38 }; 39 char StripGCRelocates::ID = 0; 40 } 41 42 bool StripGCRelocates::runOnFunction(Function &F) { 43 // Nothing to do for declarations. 44 if (F.isDeclaration()) 45 return false; 46 SmallVector<GCRelocateInst *, 20> GCRelocates; 47 // TODO: We currently do not handle gc.relocates that are in landing pads, 48 // i.e. not bound to a single statepoint token. 49 for (Instruction &I : instructions(F)) { 50 if (auto *GCR = dyn_cast<GCRelocateInst>(&I)) 51 if (isa<GCStatepointInst>(GCR->getOperand(0))) 52 GCRelocates.push_back(GCR); 53 } 54 // All gc.relocates are bound to a single statepoint token. The order of 55 // visiting gc.relocates for deletion does not matter. 56 for (GCRelocateInst *GCRel : GCRelocates) { 57 Value *OrigPtr = GCRel->getDerivedPtr(); 58 Value *ReplaceGCRel = OrigPtr; 59 60 // All gc_relocates are i8 addrspace(1)* typed, we need a bitcast from i8 61 // addrspace(1)* to the type of the OrigPtr, if the are not the same. 62 if (GCRel->getType() != OrigPtr->getType()) 63 ReplaceGCRel = new BitCastInst(OrigPtr, GCRel->getType(), "cast", GCRel); 64 65 // Replace all uses of gc.relocate and delete the gc.relocate 66 // There maybe unncessary bitcasts back to the OrigPtr type, an instcombine 67 // pass would clear this up. 68 GCRel->replaceAllUsesWith(ReplaceGCRel); 69 GCRel->eraseFromParent(); 70 } 71 return !GCRelocates.empty(); 72 } 73 74 INITIALIZE_PASS(StripGCRelocates, "strip-gc-relocates", 75 "Strip gc.relocates inserted through RewriteStatepointsForGC", 76 true, false) 77