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
17namespace llvm {
18class CallBase;
19class CastInst;
20class Function;
21class 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.
30bool 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.
40CallBase &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.
50CallBase &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///
74bool tryPromoteCall(CallBase &CB);
75
76} // end namespace llvm
77
78#endif // LLVM_TRANSFORMS_UTILS_CALLPROMOTIONUTILS_H
79