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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18077 91177308-0d34-0410-b5e6-96231b3b80d8
138 lines
5.0 KiB
C++
138 lines
5.0 KiB
C++
//===-- llvm/CodeGen/MachineRelocation.h - Target Relocation ----*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the MachineRelocation class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_MACHINERELOCATION_H
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#define LLVM_CODEGEN_MACHINERELOCATION_H
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#include "llvm/Support/DataTypes.h"
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#include <cassert>
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namespace llvm {
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class GlobalValue;
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/// MachineRelocation - This represents a target-specific relocation value,
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/// produced by the code emitter. This relocation is resolved after the has
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/// been emitted, either to an object file or to memory, when the target of the
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/// relocation can be resolved.
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///
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/// A relocation is made up of the following logical portions:
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/// 1. An offset in the machine code buffer, the location to modify.
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/// 2. A target specific relocation type (a number from 0 to 63).
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/// 3. A symbol being referenced, either as a GlobalValue* or as a string.
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/// 4. An optional constant value to be added to the reference.
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/// 5. A bit, CanRewrite, which indicates to the JIT that a function stub is
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/// not needed for the relocation.
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///
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class MachineRelocation {
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/// OffsetTypeExternal - The low 24-bits of this value is the offset from the
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/// start of the code buffer of the relocation to perform. Bit 24 of this is
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/// set if Target should use ExtSym instead of GV, Bit 25 is the CanRewrite
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/// bit, and the high 6 bits hold the relocation type.
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unsigned OffsetTypeExternal;
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union {
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GlobalValue *GV; // If this is a pointer to an LLVM global
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const char *ExtSym; // If this is a pointer to a named symbol
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void *Result; // If this has been resolved to a resolved pointer
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} Target;
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intptr_t ConstantVal;
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public:
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MachineRelocation(unsigned Offset, unsigned RelocationType, GlobalValue *GV,
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intptr_t cst = 0, bool DoesntNeedFunctionStub = 0)
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: OffsetTypeExternal(Offset + (RelocationType << 26)), ConstantVal(cst) {
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assert((Offset & ~((1 << 24)-1)) == 0 && "Code offset too large!");
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assert((RelocationType & ~63) == 0 && "Relocation type too large!");
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Target.GV = GV;
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if (DoesntNeedFunctionStub)
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OffsetTypeExternal |= 1 << 25;
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}
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MachineRelocation(unsigned Offset, unsigned RelocationType, const char *ES,
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intptr_t cst = 0)
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: OffsetTypeExternal(Offset + (1 << 24) + (RelocationType << 26)),
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ConstantVal(cst) {
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assert((Offset & ~((1 << 24)-1)) == 0 && "Code offset too large!");
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assert((RelocationType & ~63) == 0 && "Relocation type too large!");
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Target.ExtSym = ES;
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}
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/// getMachineCodeOffset - Return the offset into the code buffer that the
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/// relocation should be performed.
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unsigned getMachineCodeOffset() const {
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return OffsetTypeExternal & ((1 << 24)-1);
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}
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/// getRelocationType - Return the target-specific relocation ID for this
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/// relocation.
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unsigned getRelocationType() const {
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return OffsetTypeExternal >> 26;
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}
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/// getConstantVal - Get the constant value associated with this relocation.
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/// This is often an offset from the symbol.
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///
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intptr_t getConstantVal() const {
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return ConstantVal;
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}
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/// isGlobalValue - Return true if this relocation is a GlobalValue, as
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/// opposed to a constant string.
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bool isGlobalValue() const {
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return (OffsetTypeExternal & (1 << 24)) == 0;
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}
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/// isString - Return true if this is a constant string.
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///
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bool isString() const {
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return !isGlobalValue();
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}
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/// doesntNeedFunctionStub - This function returns true if the JIT for this
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/// target is capable of directly handling the relocated instruction without
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/// using a stub function. It is always conservatively correct for this flag
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/// to be false, but targets can improve their compilation callback functions
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/// to handle more general cases if they want improved performance.
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bool doesntNeedFunctionStub() const {
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return (OffsetTypeExternal & (1 << 25)) != 0;
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}
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/// getGlobalValue - If this is a global value reference, return the
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/// referenced global.
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GlobalValue *getGlobalValue() const {
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assert(isGlobalValue() && "This is not a global value reference!");
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return Target.GV;
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}
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/// getString - If this is a string value, return the string reference.
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///
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const char *getString() const {
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assert(isString() && "This is not a string reference!");
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return Target.ExtSym;
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}
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/// getResultPointer - Once this has been resolved to point to an actual
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/// address, this returns the pointer.
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void *getResultPointer() const {
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return Target.Result;
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}
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/// setResultPointer - Set the result to the specified pointer value.
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///
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void setResultPointer(void *Ptr) {
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Target.Result = Ptr;
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}
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};
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}
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#endif
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