https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112478
Bug ID: 112478
Summary: riscv: asm clobbers not honored
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: Michael at MichaelKloos dot com
Target Milestone: ---
A recent commit (bisected):
71f906498ada9ec2780660b03bd6e27a93ad350c
RISC-V: far-branch: Handle far jumps and branches for functions larger than 1MB
Seems to have broken call inline asm clobbers for for the $ra register.
I attempted to build a riscv32-rv32ia3-linux-musl cross compiler on a
x86_64-pc-linux-gnu system. I succeeded in building the compiler and using it
to build my target binary. However, the target binary was crashing. On
inspection, I discovered that __muldi3 from libgcc was calling __mulsi3, but
not saving the ra (link) register. Upon return from __mulsi3, an infinate loop
was entered between the reentry point and the end of the function, as the
return instruction was now pointing back at the reentry point. The
intermediate code formed a loop that moved and loaded data off the stack
pointer until the program segfaulted. libgcc makes the call to __mulsi3 with
inline assembly and sets ra as one of the clobbered registers.
Some of the configure options used are --disable-multilib --with-arch=rv32ia
--with-abi=ilp32 --enable-checking=none
--enable-checking=none is there to work around another build-time bug which I
will file separately.
If you need more information, let me know.
