I am working on a baremetal riscv toolchain using LLVM runtime and
LLD linker. Baremetal.cpp provides most of the things needed for such
toolchain. So I have modified it to also handle riscv64/32-unknown-elf
targets alongside arm-none-eabi.
Currently, targets like riscv64-unknown-elf are handled by RISCVToolChain
which mostly expects a gcc toolchain to be present. If you dont
want the dependency on gcc-toolchain/libgloss or want to use LLD, then
RISCVToolChain is not a good fit.
So in the toolchain selection code, I have made this dependency of
RISCVToolChain on gcc toolchain explicit. It is created if gcc-toolchain
option is present. Otherwise Baremetal toolchain is created. I will be
happy to hear if there is a better way to choose between these two
toolchains.
Reviewed By: jroelofs
Differential Revision: https://reviews.llvm.org/D91442
Summary:
Clang/LLVM is a cross-compiler, and so we don't have to make a choice
about `-march`/`-mabi` at build-time, but we may have to compute a
default `-march`/`-mabi` when compiling a program. Until now, each
place that has needed a default `-march` has calculated one itself.
This patch adds a single place where a default `-march` is calculated,
in order to avoid calculating different defaults in different places.
This patch adds a new function `riscv::getRISCVArch` which encapsulates
this logic based on GCC's for computing a default `-march` value
when none is provided. This patch also updates the logic in
`riscv::getRISCVABI` to match the logic in GCC's build system for
computing a default `-mabi`.
This patch also updates anywhere that `-march` is used to now use the
new function which can compute a default. In particular, we now
explicitly pass a `-march` value down to the gnu assembler.
GCC has convoluted logic in its build system to choose a default
`-march`/`-mabi` based on build options, which would be good to match.
This patch is based on the logic in GCC 9.2.0. This commit's logic is
different to GCC's only for baremetal targets, where we default
to rv32imac/ilp32 or rv64imac/lp64 depending on the target triple.
Tests have been updated to match the new logic.
Reviewers: asb, luismarques, rogfer01, kito-cheng, khchen
Reviewed By: asb, luismarques
Subscribers: sameer.abuasal, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, shiva0217, jrtc27, MaskRay, zzheng, edward-jones, MartinMosbeck, brucehoult, the_o, rkruppe, PkmX, jocewei, psnobl, benna, Jim, s.egerton, pzheng, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D69383
When using -fno-integrated-as flag, the gnu assembler produces code
with some default march/mabi which later causes linker failure due
to incompatible mabi/march.
In this patch we explicitly propagate -mabi and -march flags to the
GNU assembler.
In this patch we explicitly propagate -mabi and -march flags to the GNU assembler.
Differential Revision: https://reviews.llvm.org/D41271
llvm-svn: 322769
Hafiz Abid Qadeer