1 //===------- SEHFrameSupport.h - JITLink seh-frame utils --------*- 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 // SEHFrame utils for JITLink.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_EXECUTIONENGINE_JITLINK_SEHFRAMESUPPORT_H
14 #define LLVM_EXECUTIONENGINE_JITLINK_SEHFRAMESUPPORT_H
15 
16 #include "llvm/ExecutionEngine/JITLink/JITLink.h"
17 #include "llvm/ExecutionEngine/JITSymbol.h"
18 #include "llvm/Support/Error.h"
19 #include "llvm/TargetParser/Triple.h"
20 
21 namespace llvm {
22 namespace jitlink {
23 /// This pass adds keep-alive edge from SEH frame sections
24 /// to the parent function content block.
25 class SEHFrameKeepAlivePass {
26 public:
27   SEHFrameKeepAlivePass(StringRef SEHFrameSectionName)
28       : SEHFrameSectionName(SEHFrameSectionName) {}
29 
30   Error operator()(LinkGraph &G) {
31     auto *S = G.findSectionByName(SEHFrameSectionName);
32     if (!S)
33       return Error::success();
34 
35     // Simply consider every block pointed by seh frame block as parants.
36     // This adds some unnecessary keep-alive edges to unwind info blocks,
37     // (xdata) but these blocks are usually dead by default, so they wouldn't
38     // count for the fate of seh frame block.
39     for (auto *B : S->blocks()) {
40       auto &DummySymbol = G.addAnonymousSymbol(*B, 0, 0, false, false);
41       DenseSet<Block *> Children;
42       for (auto &E : B->edges()) {
43         auto &Sym = E.getTarget();
44         if (!Sym.isDefined())
45           continue;
46         Children.insert(&Sym.getBlock());
47       }
48       for (auto *Child : Children)
49         Child->addEdge(Edge(Edge::KeepAlive, 0, DummySymbol, 0));
50     }
51     return Error::success();
52   }
53 
54 private:
55   StringRef SEHFrameSectionName;
56 };
57 
58 } // end namespace jitlink
59 } // end namespace llvm
60 
61 #endif // LLVM_EXECUTIONENGINE_JITLINK_SEHFRAMESUPPORT_H
62