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
56namespace llvm {
57
58class Module;
59
60// Pass that converts lookup tables to relative lookup tables.
61class RelLookupTableConverterPass
62 : public PassInfoMixin<RelLookupTableConverterPass> {
63public:
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