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/Module.h" 55 #include "llvm/IR/PassManager.h" 56 57 namespace llvm { 58 59 // Pass that converts lookup tables to relative lookup tables. 60 class RelLookupTableConverterPass 61 : public PassInfoMixin<RelLookupTableConverterPass> { 62 public: 63 RelLookupTableConverterPass() = default; 64 65 PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM); 66 }; 67 68 } // end namespace llvm 69 70 #endif // LLVM_TRANSFORMS_UTILS_RELLOOKUPTABLECONVERTER_H 71