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/Pass.h" 22 #include "llvm/Support/raw_ostream.h" 23 24 using namespace llvm; 25 26 namespace { 27 struct StripGCRelocates : public FunctionPass { 28 static char ID; // Pass identification, replacement for typeid 29 StripGCRelocates() : FunctionPass(ID) { 30 initializeStripGCRelocatesPass(*PassRegistry::getPassRegistry()); 31 } 32 33 void getAnalysisUsage(AnalysisUsage &Info) const override {} 34 35 bool runOnFunction(Function &F) override; 36 37 }; 38 char StripGCRelocates::ID = 0; 39 } 40 41 bool StripGCRelocates::runOnFunction(Function &F) { 42 // Nothing to do for declarations. 43 if (F.isDeclaration()) 44 return false; 45 SmallVector<GCRelocateInst *, 20> GCRelocates; 46 // TODO: We currently do not handle gc.relocates that are in landing pads, 47 // i.e. not bound to a single statepoint token. 48 for (Instruction &I : instructions(F)) { 49 if (auto *GCR = dyn_cast<GCRelocateInst>(&I)) 50 if (isStatepoint(GCR->getOperand(0))) 51 GCRelocates.push_back(GCR); 52 } 53 // All gc.relocates are bound to a single statepoint token. The order of 54 // visiting gc.relocates for deletion does not matter. 55 for (GCRelocateInst *GCRel : GCRelocates) { 56 Value *OrigPtr = GCRel->getDerivedPtr(); 57 Value *ReplaceGCRel = OrigPtr; 58 59 // All gc_relocates are i8 addrspace(1)* typed, we need a bitcast from i8 60 // addrspace(1)* to the type of the OrigPtr, if the are not the same. 61 if (GCRel->getType() != OrigPtr->getType()) 62 ReplaceGCRel = new BitCastInst(OrigPtr, GCRel->getType(), "cast", GCRel); 63 64 // Replace all uses of gc.relocate and delete the gc.relocate 65 // There maybe unncessary bitcasts back to the OrigPtr type, an instcombine 66 // pass would clear this up. 67 GCRel->replaceAllUsesWith(ReplaceGCRel); 68 GCRel->eraseFromParent(); 69 } 70 return !GCRelocates.empty(); 71 } 72 73 INITIALIZE_PASS(StripGCRelocates, "strip-gc-relocates", 74 "Strip gc.relocates inserted through RewriteStatepointsForGC", 75 true, false) 76