LLVM  11.0.0git
CallPromotionUtils.h
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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
This class represents lattice values for constants.
Definition: AllocatorList.h:23
bool isLegalToPromote(const CallBase &CB, Function *Callee, const char **FailureReason=nullptr)
Return true if the given indirect call site can be made to call Callee.
CallBase & promoteCall(CallBase &CB, Function *Callee, CastInst **RetBitCast=nullptr)
Promote the given indirect call site to unconditionally call Callee.
CallBase & promoteCallWithIfThenElse(CallBase &CB, Function *Callee, MDNode *BranchWeights=nullptr)
Promote the given indirect call site to conditionally call Callee.
amdgpu Simplify well known AMD library false FunctionCallee Callee
bool tryPromoteCall(CallBase &CB)
Try to promote (devirtualize) a virtual call on an Alloca.