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/*
* Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2016, 2018 SAP SE. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#ifndef CPU_S390_RELOCINFO_S390_HPP
#define CPU_S390_RELOCINFO_S390_HPP
//----------------------------
// relocInfo layout
//----------------------------
// This description should be contained in code/relocInfo.hpp
// but was put here to minimize shared code diffs.
// Relocation information for a nmethod is stored in compressed
// form in an array of element type short int (16 bits).
// Each array element constitutes one relocInfo record.
// The layout of one such record is described here.
// +------------+---+---+------------------------------+
// | type | fmt | offset/offset_unit |
// +------------+---+---+------------------------------+
//
// |<-- value_width (16) ----------------------------->|
// |<type_width>|<-- nontype_width (12) -------------->|
// (4)
// | |<--+-->|<-- offset_width (10) ------->|
// / \
// / (2) \
// /<--format->\
// | width |
// only for type == data_prefix_tag:
// +------------+---+---+------------------------------+
// | type | | data |
// +------------+---+---+------------------------------+
// | 15 |<->|<-- datalen_width (11) ---------->|
// |
// +--datalen_tag (1)
// relocType
// The type field holds a value of relocType (which is
// an enum of all possible relocation types). Currently,
// there are 16 distinct relocation types, requiring
// type_width to be (at least) 4.
// relocFormat
// The format field holds a value of relocFormat (which is
// an enum of all possible relocation formats). Currently,
// there are 4 distinct relocation formats, requiring
// format_width to be (at least) 2.
// offset
// Each relocInfo is related to one specific address in the CodeBlob.
// The address always points to the first byte of the target instruction.
// It does NOT refer directly to the relocation subfield or embedded constant.
// offset contains the distance of this relocInfo from the previous one.
// offset is scaled by offset_unit (the platform-specific instruction
// alignment requirement) to maximize the encodable distance.
// To obtain the absolute address in the CodeBlob the relocInfo is
// related to, you have to iterate over all relocInfos from the
// beginning, and then use RelocIterator::addr() to get the address.
// relocType == data_prefix_tag
// These are relocInfo records containing inline data that belongs to
// the next non-data relocInfo record. Usage of that inline data is
// specific and private to that relocInfo record.
// For details refer to code/relocInfo.hpp
// machine-dependent parts of class relocInfo
private:
enum {
// Instructions are HW (2-byte) aligned on z/Architecture.
offset_unit = 2,
// Encodes Assembler::disp32_operand vs. Assembler::imm64_operand.
// (Assembler::call32_operand is used on call instructions only.)
format_width = 2
};
public:
enum relocFormat {
no_format = 0,
uncompressed_format = 0, // Relocation is for a regular oop.
compressed_format = 1, // Relocation is for a narrow (compressed) oop or klass.
// Similar to relocInfo::narrow_oop_in_const.
pcrel_addr_format = 2, // Relocation is for the target LOCATION of a pc-relative instruction.
pcrel_data_format = 3 // Relocation is for the target data of a pc-relative instruction.
};
// This platform has no oops in the code that are not also
// listed in the oop section.
static bool mustIterateImmediateOopsInCode() { return false; }
#endif // CPU_S390_RELOCINFO_S390_HPP
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