1 //=== WebAssemblyLowerRefTypesIntPtrConv.cpp -
2 //                     Lower IntToPtr and PtrToInt on Reference Types   ---===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9 ///
10 /// \file
11 /// Lowers IntToPtr and PtrToInt instructions on reference types to
12 /// Trap instructions since they have been allowed to operate
13 /// on non-integral pointers.
14 ///
15 //===----------------------------------------------------------------------===//
16 
17 #include "Utils/WebAssemblyTypeUtilities.h"
18 #include "WebAssembly.h"
19 #include "WebAssemblySubtarget.h"
20 #include "llvm/IR/InstIterator.h"
21 #include "llvm/Pass.h"
22 
23 using namespace llvm;
24 
25 #define DEBUG_TYPE "wasm-lower-reftypes-intptr-conv"
26 
27 namespace {
28 class WebAssemblyLowerRefTypesIntPtrConv final : public FunctionPass {
29   StringRef getPassName() const override {
30     return "WebAssembly Lower RefTypes Int-Ptr Conversions";
31   }
32 
33   bool runOnFunction(Function &MF) override;
34 
35 public:
36   static char ID; // Pass identification
37   WebAssemblyLowerRefTypesIntPtrConv() : FunctionPass(ID) {}
38 };
39 } // end anonymous namespace
40 
41 char WebAssemblyLowerRefTypesIntPtrConv::ID = 0;
42 INITIALIZE_PASS(WebAssemblyLowerRefTypesIntPtrConv, DEBUG_TYPE,
43                 "WebAssembly Lower RefTypes Int-Ptr Conversions", false, false)
44 
45 FunctionPass *llvm::createWebAssemblyLowerRefTypesIntPtrConv() {
46   return new WebAssemblyLowerRefTypesIntPtrConv();
47 }
48 
49 bool WebAssemblyLowerRefTypesIntPtrConv::runOnFunction(Function &F) {
50   LLVM_DEBUG(dbgs() << "********** Lower RefTypes IntPtr Convs **********\n"
51                        "********** Function: "
52                     << F.getName() << '\n');
53 
54   // This function will check for uses of ptrtoint and inttoptr on reference
55   // types and replace them with a trap instruction.
56   //
57   // We replace the instruction by a trap instruction
58   // and its uses by null in the case of inttoptr and 0 in the
59   // case of ptrtoint.
60   std::set<Instruction *> worklist;
61 
62   for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I) {
63     PtrToIntInst *PTI = dyn_cast<PtrToIntInst>(&*I);
64     IntToPtrInst *ITP = dyn_cast<IntToPtrInst>(&*I);
65     if (!(PTI && WebAssembly::isWebAssemblyReferenceType(
66                      PTI->getPointerOperand()->getType())) &&
67         !(ITP && WebAssembly::isWebAssemblyReferenceType(ITP->getDestTy())))
68       continue;
69 
70     UndefValue *U = UndefValue::get(I->getType());
71     I->replaceAllUsesWith(U);
72 
73     Function *TrapIntrin =
74         Intrinsic::getDeclaration(F.getParent(), Intrinsic::debugtrap);
75     CallInst::Create(TrapIntrin, {}, "", &*I);
76 
77     worklist.insert(&*I);
78   }
79 
80   // erase each instruction replaced by trap
81   for (Instruction *I : worklist)
82     I->eraseFromParent();
83 
84   return !worklist.empty();
85 }
86