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 class Value; 23 24 /// Return true if the given indirect call site can be made to call \p Callee. 25 /// 26 /// This function ensures that the number and type of the call site's arguments 27 /// and return value match those of the given function. If the types do not 28 /// match exactly, they must at least be bitcast compatible. If \p FailureReason 29 /// is non-null and the indirect call cannot be promoted, the failure reason 30 /// will be stored in it. 31 bool isLegalToPromote(const CallBase &CB, Function *Callee, 32 const char **FailureReason = nullptr); 33 34 /// Promote the given indirect call site to unconditionally call \p Callee. 35 /// 36 /// This function promotes the given call site, returning the direct call or 37 /// invoke instruction. If the function type of the call site doesn't match that 38 /// of the callee, bitcast instructions are inserted where appropriate. If \p 39 /// RetBitCast is non-null, it will be used to store the return value bitcast, 40 /// if created. 41 CallBase &promoteCall(CallBase &CB, Function *Callee, 42 CastInst **RetBitCast = nullptr); 43 44 /// Promote the given indirect call site to conditionally call \p Callee. 45 /// 46 /// This function creates an if-then-else structure at the location of the call 47 /// site. The original call site is moved into the "else" block. A clone of the 48 /// indirect call site is promoted, placed in the "then" block, and returned. If 49 /// \p BranchWeights is non-null, it will be used to set !prof metadata on the 50 /// new conditional branch. 51 CallBase &promoteCallWithIfThenElse(CallBase &CB, Function *Callee, 52 MDNode *BranchWeights = nullptr); 53 54 /// Try to promote (devirtualize) a virtual call on an Alloca. Return true on 55 /// success. 56 /// 57 /// Look for a pattern like: 58 /// 59 /// %o = alloca %class.Impl 60 /// %1 = getelementptr %class.Impl, %class.Impl* %o, i64 0, i32 0, i32 0 61 /// store i32 (...)** bitcast (i8** getelementptr inbounds 62 /// ({ [3 x i8*] }, { [3 x i8*] }* @_ZTV4Impl, i64 0, inrange i32 0, i64 2) 63 /// to i32 (...)**), i32 (...)*** %1 64 /// %2 = getelementptr inbounds %class.Impl, %class.Impl* %o, i64 0, i32 0 65 /// %3 = bitcast %class.Interface* %2 to void (%class.Interface*)*** 66 /// %vtable.i = load void (%class.Interface*)**, void (%class.Interface*)*** %3 67 /// %4 = load void (%class.Interface*)*, void (%class.Interface*)** %vtable.i 68 /// call void %4(%class.Interface* nonnull %2) 69 /// 70 /// @_ZTV4Impl = linkonce_odr dso_local unnamed_addr constant { [3 x i8*] } 71 /// { [3 x i8*] 72 /// [i8* null, i8* bitcast ({ i8*, i8*, i8* }* @_ZTI4Impl to i8*), 73 /// i8* bitcast (void (%class.Impl*)* @_ZN4Impl3RunEv to i8*)] } 74 /// 75 bool tryPromoteCall(CallBase &CB); 76 77 /// Predicate and clone the given call site. 78 /// 79 /// This function creates an if-then-else structure at the location of the call 80 /// site. The "if" condition compares the call site's called value to the given 81 /// callee. The original call site is moved into the "else" block, and a clone 82 /// of the call site is placed in the "then" block. The cloned instruction is 83 /// returned. 84 CallBase &versionCallSite(CallBase &CB, Value *Callee, MDNode *BranchWeights); 85 86 } // end namespace llvm 87 88 #endif // LLVM_TRANSFORMS_UTILS_CALLPROMOTIONUTILS_H 89