path: root/arch/arm/atomic_arch.h
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2017-10-25fix build regression on ARM for ISA levels less than v5Rich Felker-0/+4
commit 06fbefd10046a0fae7e588b7c6d25fb51811b931 (first included in release 1.1.17) introduced this regression. patch by Adrian Bunk. it fixes the regression in all cases, but spuriously prevents use of the clz instruction on very old compiler versions that don't define __ARM_ARCH. this may be fixed in a more general way at some point in the future. it also omits thumb1 logic since building as thumb1 code is currently not supported.
2017-08-29add a_clz_64 helper functionSzabolcs Nagy-0/+7
counts leading zero bits of a 64bit int, undefined on zero input. (has nothing to do with atomics, added to atomic.h so target specific helper functions are together.) there is a logarithmic generic implementation and another in terms of a 32bit a_clz_32 on targets where that's available.
2016-12-19rework arm atomic/tp backends to be thumb-compatible and fdpic-readyRich Felker-7/+14
three problems are addressed: - use of pc arithmetic, which was difficult if not impossible to make correct in thumb mode on all models, so that relative rather than absolute pointers to the backends could be used. this was designed back when there was no coherent model for the early stages of the dynamic linker before relocations, and is no longer necessary. - assumption that data (the relative pointers to the backends) can be accessed at a constant displacement from the code. this will not be possible on future fdpic subarchs (for cortex-m), so move responsibility for loading the backend code address to the caller. - hard-coded arm opcodes using the .word directive. instead, use the .arch directive to work around the assembler's refusal to assemble instructions not available (or in some cases, available but just considered deprecated) in the target isa level. the obscure v6t2 arch is used for v6 code so as to (1) allow generation of thumb2 output if -mthumb is active, and (2) avoid warnings/errors for mcr barriers that clang would produce if we just set arch to v7-a. in addition, the __aeabi_read_tp function is moved out of the inner workings and implemented as an asm wrapper around a C function, so that asm code does not need to read global data. the asm wrapper serves to satisfy the ABI calling convention requirements for this function.
2016-01-31better a_sc inline asm constraint on aarch64 and armSzabolcs Nagy-1/+1
"Q" input constraint was used for the written object, instead of "=Q" output constraint. this should not cause problems because "memory" is on the clobber list, but "=Q" better documents the intent and more consistent with the actual asm code. this changes the generated code, because different registers are used, but other than the register names nothing should change.
2016-01-25fix arm a_crash for big endianRich Felker-2/+4
contrary to commit 89e149d275a7699a4a5e4c98bab267648f64cbba, big endian arm does need the instruction bytes in big endian order. rather than trying to use a special encoding that works as arm or thumb, simply encode the simplest/canonical undefined instructions dependent on whether __thumb__ is defined.
2016-01-25add native a_crash primitive for armRich Felker-0/+10
the .byte directive encodes a guaranteed-undefined instruction, the same one Linux fills the kuser helper page with when it's disabled. the udf mnemonic and and .insn directives are not supported by old binutils versions, and larger-than-byte integer directives would produce the wrong output on big-endian.
2016-01-21overhaul arm atomics for new atomics frameworkRich Felker-142/+38
switch to ll/sc model so that new atomic.h can provide optimized versions of all the atomic primitives without needing an ll/sc loop written in asm for each one. all isa levels which use ldrex/strex now use the inline ll/sc model even if the type of barrier to use is not known until runtime (v6). the cas model is only used for arm v5 and earlier, and it has been optimized to make the call via inline asm with custom constraints rather than as a C function call.
2016-01-21refactor internal atomic.hRich Felker-0/+168
rather than having each arch provide its own atomic.h, there is a new shared atomic.h in src/internal which pulls arch-specific definitions from arc/$(ARCH)/atomic_arch.h. the latter can be extremely minimal, defining only a_cas or new ll/sc type primitives which the shared atomic.h will use to construct everything else. this commit avoids making heavy changes to the individual archs' atomic implementations. definitions which are identical or near-identical to what the new shared atomic.h would produce have been removed, but otherwise the changes made are just hooking up the arch-specific files to the new infrastructure. major changes to take advantage of the new system will come in subsequent commits.