| //===-- RelLookupTableConverterPass.h - Rel Table Conv ----------*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| /// \file |
| /// This file implements relative lookup table converter that converts |
| /// lookup tables to relative lookup tables to make them PIC-friendly. |
| /// |
| /// Switch lookup table example: |
| /// @switch.table.foo = private unnamed_addr constant [3 x i8*] |
| /// [ |
| /// i8* getelementptr inbounds ([5 x i8], [5 x i8]* @.str, i64 0, i64 0), |
| /// i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.1, i64 0, i64 0), |
| /// i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str.2, i64 0, i64 0) |
| /// ], align 8 |
| /// |
| /// switch.lookup: |
| /// %1 = sext i32 %cond to i64 |
| /// %switch.gep = getelementptr inbounds [3 x i8*], |
| /// [3 x i8*]* @switch.table.foo, i64 0, i64 %1 |
| /// %switch.load = load i8*, i8** %switch.gep, align 8 |
| /// ret i8* %switch.load |
| /// |
| /// Switch lookup table will become a relative lookup table that |
| /// consists of relative offsets. |
| /// |
| /// @reltable.foo = private unnamed_addr constant [3 x i32] |
| /// [ |
| /// i32 trunc (i64 sub (i64 ptrtoint ([5 x i8]* @.str to i64), |
| /// i64 ptrtoint ([3 x i32]* @reltable.foo to i64)) to i32), |
| /// i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.1 to i64), |
| /// i64 ptrtoint ([3 x i32]* @reltable.foo to i64)) to i32), |
| /// i32 trunc (i64 sub (i64 ptrtoint ([4 x i8]* @.str.2 to i64), |
| /// i64 ptrtoint ([3 x i32]* @reltable.foo to i64)) to i32) |
| /// ], align 4 |
| /// |
| /// IR after converting to a relative lookup table: |
| /// switch.lookup: |
| /// %1 = sext i32 %cond to i64 |
| /// %reltable.shift = shl i64 %1, 2 |
| /// %reltable.intrinsic = call i8* @llvm.load.relative.i64( |
| /// i8* bitcast ([3 x i32]* @reltable.foo to i8*), |
| /// i64 %reltable.shift) |
| /// ret i8* %reltable.intrinsic |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_TRANSFORMS_UTILS_RELLOOKUPTABLECONVERTER_H |
| #define LLVM_TRANSFORMS_UTILS_RELLOOKUPTABLECONVERTER_H |
| |
| #include "llvm/IR/PassManager.h" |
| |
| namespace llvm { |
| |
| class Module; |
| |
| // Pass that converts lookup tables to relative lookup tables. |
| class RelLookupTableConverterPass |
| : public PassInfoMixin<RelLookupTableConverterPass> { |
| public: |
| RelLookupTableConverterPass() = default; |
| |
| PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM); |
| }; |
| |
| } // end namespace llvm |
| |
| #endif // LLVM_TRANSFORMS_UTILS_RELLOOKUPTABLECONVERTER_H |