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 class CallBase; 19 class CastInst; 20 class Function; 21 class MDNode; 22 23 /// Return true if the given indirect call site can be made to call \p Callee. 24 /// 25 /// This function ensures that the number and type of the call site's arguments 26 /// and return value match those of the given function. If the types do not 27 /// match exactly, they must at least be bitcast compatible. If \p FailureReason 28 /// is non-null and the indirect call cannot be promoted, the failure reason 29 /// will be stored in it. 30 bool isLegalToPromote(const CallBase &CB, Function *Callee, 31 const char **FailureReason = nullptr); 32 33 /// Promote the given indirect call site to unconditionally call \p Callee. 34 /// 35 /// This function promotes the given call site, returning the direct call or 36 /// invoke instruction. If the function type of the call site doesn't match that 37 /// of the callee, bitcast instructions are inserted where appropriate. If \p 38 /// RetBitCast is non-null, it will be used to store the return value bitcast, 39 /// if created. 40 CallBase &promoteCall(CallBase &CB, Function *Callee, 41 CastInst **RetBitCast = nullptr); 42 43 /// Promote the given indirect call site to conditionally call \p Callee. 44 /// 45 /// This function creates an if-then-else structure at the location of the call 46 /// site. The original call site is moved into the "else" block. A clone of the 47 /// indirect call site is promoted, placed in the "then" block, and returned. If 48 /// \p BranchWeights is non-null, it will be used to set !prof metadata on the 49 /// new conditional branch. 50 CallBase &promoteCallWithIfThenElse(CallBase &CB, Function *Callee, 51 MDNode *BranchWeights = nullptr); 52 53 /// Try to promote (devirtualize) a virtual call on an Alloca. Return true on 54 /// success. 55 /// 56 /// Look for a pattern like: 57 /// 58 /// %o = alloca %class.Impl 59 /// %1 = getelementptr %class.Impl, %class.Impl* %o, i64 0, i32 0, i32 0 60 /// store i32 (...)** bitcast (i8** getelementptr inbounds 61 /// ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV4Impl, i64 0, inrange i32 0, i64 2) 62 /// to i32 (...)**), i32 (...)*** %1 63 /// %2 = getelementptr inbounds %class.Impl, %class.Impl* %o, i64 0, i32 0 64 /// %3 = bitcast %class.Interface* %2 to void (%class.Interface*)*** 65 /// %vtable.i = load void (%class.Interface*)**, void (%class.Interface*)*** %3 66 /// %4 = load void (%class.Interface*)*, void (%class.Interface*)** %vtable.i 67 /// call void %4(%class.Interface* nonnull %2) 68 /// 69 /// @_ZTV4Impl = linkonce_odr dso_local unnamed_addr constant { [3 x i8*] } 70 /// { [3 x i8*] 71 /// [i8* null, i8* bitcast ({ i8*, i8*, i8* }* @_ZTI4Impl to i8*), 72 /// i8* bitcast (void (%class.Impl*)* @_ZN4Impl3RunEv to i8*)] } 73 /// 74 bool tryPromoteCall(CallBase &CB); 75 76 } // end namespace llvm 77 78 #endif // LLVM_TRANSFORMS_UTILS_CALLPROMOTIONUTILS_H 79