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2019-07-17use register constraint instead of memory operand for riscv64 atomicsRich Felker-8/+8
the "A" constraint is simply for an address expression that's a single register, but it's not yet supported by clang, and has no advantage here over just using a register operand for the address. the latter is actually preferable in the a_cas_p case because it avoids aliasing an lvalue onto the memory.
2019-07-17fix riscv64 atomic asm constraintsRich Felker-6/+10
most egregious problem was the lack of memory clobber and lack of volatile asm; this made the atomics memory barriers but not compiler barriers. use of "+r" rather than "=r" for a clobbered temp was also wrong, since the initial value is indeterminate.
2019-06-14add riscv64 architecture supportRich Felker-0/+34
Author: Alex Suykov <alex.suykov@gmail.com> Author: Aric Belsito <lluixhi@gmail.com> Author: Drew DeVault <sir@cmpwn.com> Author: Michael Clark <mjc@sifive.com> Author: Michael Forney <mforney@mforney.org> Author: Stefan O'Rear <sorear2@gmail.com> This port has involved the work of many people over several years. I have tried to ensure that everyone with substantial contributions has been credited above; if any omissions are found they will be noted later in an update to the authors/contributors list in the COPYRIGHT file. The version committed here comes from the riscv/riscv-musl repo's commit 3fe7e2c75df78eef42dcdc352a55757729f451e2, with minor changes by me for issues found during final review: - a_ll/a_sc atomics are removed (according to the ISA spec, lr/sc are not safe to use in separate inline asm fragments) - a_cas[_p] is fixed to be a memory barrier - the call from the _start assembly into the C part of crt1/ldso is changed to allow for the possibility that the linker does not place them nearby each other. - DTP_OFFSET is defined correctly so that local-dynamic TLS works - reloc.h LDSO_ARCH logic is simplified and made explicit. - unused, non-functional crti/n asm files are removed. - an empty .sdata section is added to crt1 so that the __global_pointer reference is resolvable. - indentation style errors in some asm files are fixed.