1 //===- CallPromotionUtils.h - Utilities for call promotion ------*- C++ -*-===// 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 file declares utilities useful for promoting indirect call sites to 10 // direct call sites. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_TRANSFORMS_UTILS_CALLPROMOTIONUTILS_H 15 #define LLVM_TRANSFORMS_UTILS_CALLPROMOTIONUTILS_H 16 17 namespace llvm { 18 template <typename T> class ArrayRef; 19 class Constant; 20 class CallBase; 21 class CastInst; 22 class Function; 23 class Instruction; 24 class MDNode; 25 class Value; 26 27 /// Return true if the given indirect call site can be made to call \p Callee. 28 /// 29 /// This function ensures that the number and type of the call site's arguments 30 /// and return value match those of the given function. If the types do not 31 /// match exactly, they must at least be bitcast compatible. If \p FailureReason 32 /// is non-null and the indirect call cannot be promoted, the failure reason 33 /// will be stored in it. 34 bool isLegalToPromote(const CallBase &CB, Function *Callee, 35 const char **FailureReason = nullptr); 36 37 /// Promote the given indirect call site to unconditionally call \p Callee. 38 /// 39 /// This function promotes the given call site, returning the direct call or 40 /// invoke instruction. If the function type of the call site doesn't match that 41 /// of the callee, bitcast instructions are inserted where appropriate. If \p 42 /// RetBitCast is non-null, it will be used to store the return value bitcast, 43 /// if created. 44 CallBase &promoteCall(CallBase &CB, Function *Callee, 45 CastInst **RetBitCast = nullptr); 46 47 /// Promote the given indirect call site to conditionally call \p Callee. The 48 /// promoted direct call instruction is predicated on `CB.getCalledOperand() == 49 /// Callee`. 50 /// 51 /// This function creates an if-then-else structure at the location of the call 52 /// site. The original call site is moved into the "else" block. A clone of the 53 /// indirect call site is promoted, placed in the "then" block, and returned. If 54 /// \p BranchWeights is non-null, it will be used to set !prof metadata on the 55 /// new conditional branch. 56 CallBase &promoteCallWithIfThenElse(CallBase &CB, Function *Callee, 57 MDNode *BranchWeights = nullptr); 58 59 /// This is similar to `promoteCallWithIfThenElse` except that the condition to 60 /// promote a virtual call is that \p VPtr is the same as any of \p 61 /// AddressPoints. 62 /// 63 /// This function is expected to be used on virtual calls (a subset of indirect 64 /// calls). \p VPtr is the virtual table address stored in the objects, and 65 /// \p AddressPoints contains vtable address points. A vtable address point is 66 /// a location inside the vtable that's referenced by vpointer in C++ objects. 67 /// 68 /// TODO: sink the address-calculation instructions of indirect callee to the 69 /// indirect call fallback after transformation. 70 CallBase &promoteCallWithVTableCmp(CallBase &CB, Instruction *VPtr, 71 Function *Callee, 72 ArrayRef<Constant *> AddressPoints, 73 MDNode *BranchWeights); 74 75 /// Try to promote (devirtualize) a virtual call on an Alloca. Return true on 76 /// success. 77 /// 78 /// Look for a pattern like: 79 /// 80 /// %o = alloca %class.Impl 81 /// %1 = getelementptr %class.Impl, %class.Impl* %o, i64 0, i32 0, i32 0 82 /// store i32 (...)** bitcast (i8** getelementptr inbounds 83 /// ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV4Impl, i64 0, inrange i32 0, i64 2) 84 /// to i32 (...)**), i32 (...)*** %1 85 /// %2 = getelementptr inbounds %class.Impl, %class.Impl* %o, i64 0, i32 0 86 /// %3 = bitcast %class.Interface* %2 to void (%class.Interface*)*** 87 /// %vtable.i = load void (%class.Interface*)**, void (%class.Interface*)*** %3 88 /// %4 = load void (%class.Interface*)*, void (%class.Interface*)** %vtable.i 89 /// call void %4(%class.Interface* nonnull %2) 90 /// 91 /// @_ZTV4Impl = linkonce_odr dso_local unnamed_addr constant { [3 x i8*] } 92 /// { [3 x i8*] 93 /// [i8* null, i8* bitcast ({ i8*, i8*, i8* }* @_ZTI4Impl to i8*), 94 /// i8* bitcast (void (%class.Impl*)* @_ZN4Impl3RunEv to i8*)] } 95 /// 96 bool tryPromoteCall(CallBase &CB); 97 98 /// Predicate and clone the given call site. 99 /// 100 /// This function creates an if-then-else structure at the location of the 101 /// call site. The "if" condition compares the call site's called value to 102 /// the given callee. The original call site is moved into the "else" block, 103 /// and a clone of the call site is placed in the "then" block. The cloned 104 /// instruction is returned. 105 CallBase &versionCallSite(CallBase &CB, Value *Callee, MDNode *BranchWeights); 106 107 } // end namespace llvm 108 109 #endif // LLVM_TRANSFORMS_UTILS_CALLPROMOTIONUTILS_H 110