1 | //===-- RelLookupTableConverterPass.h - Rel Table Conv ----------*- 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 | /// \file |
10 | /// This file implements relative lookup table converter that converts |
11 | /// lookup tables to relative lookup tables to make them PIC-friendly. |
12 | /// |
13 | /// Switch lookup table example: |
14 | /// @switch.table.foo = private unnamed_addr constant [3 x i8*] |
15 | /// [ |
16 | /// i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), |
17 | /// i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0), |
18 | /// i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.2, i64 0, i64 0) |
19 | /// ], align 8 |
20 | /// |
21 | /// switch.lookup: |
22 | /// %1 = sext i32 %cond to i64 |
23 | /// %switch.gep = getelementptr inbounds [3 x i8*], |
24 | /// [3 x i8*]* @switch.table.foo, i64 0, i64 %1 |
25 | /// %switch.load = load i8*, i8** %switch.gep, align 8 |
26 | /// ret i8* %switch.load |
27 | /// |
28 | /// Switch lookup table will become a relative lookup table that |
29 | /// consists of relative offsets. |
30 | /// |
31 | /// @reltable.foo = private unnamed_addr constant [3 x i32] |
32 | /// [ |
33 | /// i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str to i64), |
34 | /// i64 ptrtoint ([3 x i32]* @reltable.foo to i64)) to i32), |
35 | /// i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.1 to i64), |
36 | /// i64 ptrtoint ([3 x i32]* @reltable.foo to i64)) to i32), |
37 | /// i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.2 to i64), |
38 | /// i64 ptrtoint ([3 x i32]* @reltable.foo to i64)) to i32) |
39 | /// ], align 4 |
40 | /// |
41 | /// IR after converting to a relative lookup table: |
42 | /// switch.lookup: |
43 | /// %1 = sext i32 %cond to i64 |
44 | /// %reltable.shift = shl i64 %1, 2 |
45 | /// %reltable.intrinsic = call i8* @llvm.load.relative.i64( |
46 | /// i8* bitcast ([3 x i32]* @reltable.foo to i8*), |
47 | /// i64 %reltable.shift) |
48 | /// ret i8* %reltable.intrinsic |
49 | //===----------------------------------------------------------------------===// |
50 | |
51 | #ifndef LLVM_TRANSFORMS_UTILS_RELLOOKUPTABLECONVERTER_H |
52 | #define LLVM_TRANSFORMS_UTILS_RELLOOKUPTABLECONVERTER_H |
53 | |
54 | #include "llvm/IR/PassManager.h" |
55 | |
56 | namespace llvm { |
57 | |
58 | class Module; |
59 | |
60 | // Pass that converts lookup tables to relative lookup tables. |
61 | class RelLookupTableConverterPass |
62 | : public PassInfoMixin<RelLookupTableConverterPass> { |
63 | public: |
64 | RelLookupTableConverterPass() = default; |
65 | |
66 | PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM); |
67 | }; |
68 | |
69 | } // end namespace llvm |
70 | |
71 | #endif // LLVM_TRANSFORMS_UTILS_RELLOOKUPTABLECONVERTER_H |
72 | |