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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210443 91177308-0d34-0410-b5e6-96231b3b80d8
105 lines
3.5 KiB
C++
105 lines
3.5 KiB
C++
//===-- JumpInstrTables.h: Jump-Instruction Tables --------------*- C++ -*-===//
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// \brief An implementation of tables consisting of jump instructions
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_JUMPINSTRTABLES_H
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#define LLVM_CODEGEN_JUMPINSTRTABLES_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/Pass.h"
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#include "llvm/Target/TargetOptions.h"
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namespace llvm {
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class Constant;
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class Function;
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class FunctionType;
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class JumpInstrTableInfo;
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class Module;
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/// A class to manage a set of jump tables indexed on function type. It looks at
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/// each function in the module to find all the functions that have the
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/// jumptable attribute set. For each such function, it creates a new
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/// jump-instruction-table function and stores the mapping in the ImmutablePass
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/// JumpInstrTableInfo.
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///
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/// These special functions get lowered in AsmPrinter to assembly of the form:
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/// \verbatim
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/// .globl f
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/// .type f,@function
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/// .align 8,0x90
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/// f:
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/// jmp f_orig@PLT
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/// \endverbatim
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///
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/// Support for an architecture depends on two functions in TargetInstrInfo:
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/// getUnconditionalBranch, and getTrap. AsmPrinter uses these to generate the
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/// appropriate instructions for the jump statement (an unconditional branch)
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/// and for padding to make the table have a size that is a power of two. This
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/// padding uses a trap instruction to ensure that calls to this area halt the
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/// program. The default implementations of these functions call
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/// llvm_unreachable.
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class JumpInstrTables : public ModulePass {
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public:
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static char ID;
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JumpInstrTables();
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JumpInstrTables(JumpTable::JumpTableType JTT);
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virtual ~JumpInstrTables();
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bool runOnModule(Module &M) override;
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const char *getPassName() const override { return "Jump-Instruction Tables"; }
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void getAnalysisUsage(AnalysisUsage &AU) const override;
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/// Creates a jump-instruction table function for the Target and adds it to
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/// the tables.
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Function *insertEntry(Module &M, Function *Target);
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/// Checks to see if there is already a table for the given FunctionType.
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bool hasTable(FunctionType *FunTy);
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private:
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/// The metadata used while a jump table is being built
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struct TableMeta {
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/// The number of this table
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unsigned TableNum;
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/// The current number of jump entries in the table.
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unsigned Count;
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};
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typedef DenseMap<FunctionType *, struct TableMeta> JumpMap;
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/// Maps the function into a subset of function types, depending on the
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/// jump-instruction table style selected from JumpTableTypes in
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/// JumpInstrTables.cpp. The choice of mapping determines the number of
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/// jump-instruction tables generated by this pass. E.g., the simplest mapping
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/// converts every function type into void f(); so, all functions end up in a
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/// single table.
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FunctionType *transformType(FunctionType *FunTy);
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/// The current state of functions and jump entries in the table(s).
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JumpMap Metadata;
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/// The ImmutablePass that stores information about the generated tables.
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JumpInstrTableInfo *JITI;
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/// The total number of tables.
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unsigned TableCount;
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/// The type of tables to build.
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JumpTable::JumpTableType JTType;
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};
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/// Creates a JumpInstrTables pass for the given type of jump table.
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ModulePass *createJumpInstrTablesPass(JumpTable::JumpTableType JTT);
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}
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#endif /* LLVM_CODEGEN_JUMPINSTRTABLES_H */
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