[PATCH] D78931: [libunwind][RISCV] Track PC separately from RA

[Amanieu d'Antras via Phabricator via llvm-commits]

Amanieu added a comment.

The RISC-V unwinding spec is pretty bare: https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#dwarf

I had a look at libgcc, it tracks the PC separately from the other dwarf registers. The value modified by _Unwind_SetIP is separate from any of the values controlled by _Unwind_SetGR.

The way I am currently getting backtraces from a signal handler is to use unw_set_reg to initialize all the register from my sigcontext, and then using unw_set_reg(UNW_REG_IP) to set the PC. This only works if the PC is tracked separately from the return address register. This works fine on other targets (ARM, ARM64) where this is already the case.


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https://reviews.llvm.org/D78931