Andrew Burgess
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.
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