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634494366c
GDB relies on the fact that if two target descriptions have the same contents, then they will be the same object instance (having the same address). One place where this is a requirement is in GDBARCH_LIST_LOOKUP_BY_INFO which is used to find previously created gdbarch objects. In GDBARCH_LIST_LOOKUP_BY_INFO a pointer comparison is made on the gdbarch's target description, if the pointers are different then it is assumed the gdbarches have different, non-compatible target descriptions. Previously we would create duplicate target descriptions in the belief that RISCV_GDBARCH_INIT would spot this duplication and discard the second instance. However, this was incorrect, and instead we ended up creating duplicate gdbarch objects. With this commit every unique feature set will create one and only one target description, the feature set and resulting target description is then cached so that the same target description object can be returned later. Many other target avoid this problem by creating a small number of named target descriptions, and returning one of these. However, we currently have 8 possible target descriptions (32 vs 64 bit for x-reg and f-reg, and h/w or s/w float abi) and creating each of these just to avoid a dynamic cache seems pointless. gdb/ChangeLog: * arch/riscv.h (riscv_gdbarch_features::hash): New method. * arch/riscv.c (struct riscv_gdbarch_features_hasher): New. (riscv_tdesc_cache): New global. (riscv_create_target_description): Look in the cache before creating a new target description.
101 lines
3.3 KiB
C
101 lines
3.3 KiB
C
/* Copyright (C) 2018 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include "common-defs.h"
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#include "riscv.h"
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#include <stdlib.h>
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#include <unordered_map>
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#include "../features/riscv/32bit-cpu.c"
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#include "../features/riscv/64bit-cpu.c"
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#include "../features/riscv/32bit-fpu.c"
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#include "../features/riscv/64bit-fpu.c"
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/* Wrapper used by std::unordered_map to generate hash for feature set. */
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struct riscv_gdbarch_features_hasher
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{
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std::size_t
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operator() (const riscv_gdbarch_features &features) const noexcept
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{
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return features.hash ();
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}
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};
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/* Cache of previously seen target descriptions, indexed by the feature set
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that created them. */
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static std::unordered_map<riscv_gdbarch_features,
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target_desc *,
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riscv_gdbarch_features_hasher> riscv_tdesc_cache;
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/* See arch/riscv.h. */
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const target_desc *
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riscv_create_target_description (struct riscv_gdbarch_features features)
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{
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/* Have we seen this feature set before? If we have return the same
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target description. GDB expects that if two target descriptions are
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the same (in content terms) then they will actually be the same
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instance. This is important when trying to lookup gdbarch objects as
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GDBARCH_LIST_LOOKUP_BY_INFO performs a pointer comparison on target
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descriptions to find candidate gdbarch objects. */
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const auto it = riscv_tdesc_cache.find (features);
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if (it != riscv_tdesc_cache.end ())
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return it->second;
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/* Now we should create a new target description. */
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target_desc *tdesc = allocate_target_description ();
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#ifndef IN_PROCESS_AGENT
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std::string arch_name = "riscv";
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if (features.xlen == 4)
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arch_name.append (":rv32i");
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else if (features.xlen == 8)
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arch_name.append (":rv64i");
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else if (features.xlen == 16)
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arch_name.append (":rv128i");
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if (features.flen == 4)
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arch_name.append ("f");
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else if (features.flen == 8)
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arch_name.append ("d");
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else if (features.flen == 16)
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arch_name.append ("q");
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set_tdesc_architecture (tdesc, arch_name.c_str ());
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#endif
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long regnum = 0;
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/* For now we only support creating 32-bit or 64-bit x-registers. */
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if (features.xlen == 4)
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regnum = create_feature_riscv_32bit_cpu (tdesc, regnum);
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else if (features.xlen == 8)
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regnum = create_feature_riscv_64bit_cpu (tdesc, regnum);
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/* For now we only support creating 32-bit or 64-bit f-registers. */
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if (features.flen == 4)
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regnum = create_feature_riscv_32bit_fpu (tdesc, regnum);
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else if (features.flen == 8)
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regnum = create_feature_riscv_64bit_fpu (tdesc, regnum);
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/* Add to the cache. */
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riscv_tdesc_cache.emplace (features, tdesc);
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return tdesc;
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}
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