On Mon, Mar 11, 2024 at 11:56:42AM -0700, Richard Bagley wrote: > I have realized that *the patch is indeed a fix*, not a workaround. > > In fact, the argument to LUI and AUIPC in assembly *must* be a number > between [0x0, 0xfffff]. > RISC-V Assembly Programmer's Manual : Load Upper Immediate's Immediate > <https://github.com/riscv-non-isa/riscv-asm-manual/blob/master/riscv-asm.md#load-upper-immediates-immediate>
I think that's just documenting the current behavior, but the behavior (not accepting a signed decimal number for a signed immediate) doesn't appear to be justified, so I think my suggestion in [1] still stands. That said, I don't really have much of a horse in this race so if somebody comes along and closes that BZ with a simple justification of "we, the people that work on this stuff, agreed we prefer the range [0x0, 0xfffff]", then I won't argue. [1] https://sourceware.org/bugzilla/show_bug.cgi?id=30746 Thanks, drew > Signed decimal numbers are programmed as their two's complement. > > I checked: neither GCC nor LLVM will assemble > > > lui x1, -4 > > The LLVM compiled models the arguments to LUI and AUIPC as UIMM (unsigned > immediate) or UIMM20 (20 bit unsigned immediate). > > I should have checked this from the start. I jumped to the conclusion that > both formats (signed decimal, two's complement) for negative arguments > should be supported, and that I was encountering a bug. > I apologize to all for the unnecessary back-and-forth. > > I don't yet see a reason why llvm and gcc could not support a signed number > in decimal format, perhaps requiring a pseudo-instruction. > This might be desirable, if only in support of assembly programming. > On the other hand, it is easy to make the conversion to a two's-complement > number. > > Richard > > On Sat, Mar 9, 2024 at 4:01 AM Andrew Jones <ajo...@ventanamicro.com> wrote: > > > On Fri, Mar 08, 2024 at 08:22:01PM -0800, Richard Bagley wrote: > > > post-nack, one further comment: > > > > > > One could argue that this change also aligns QEMU with supporting tools > > (as > > > Andrew observed), and it makes sense to merge this change into QEMU until > > > those tools update to supporting signed decimal numbers with immediates. > > > > > > As it is, both GNU assembler and the LLVM integrated assembler (or > > llvm-mc) > > > throws an error with examples such as > > > auipc s0, -17 > > > > > > On the other hand, I have only seen this problem with the output of the > > > COLLECT plug-in, not (as yet) with QEMU execution proper. > > > If the problem is confined to COLLECT, perhaps the argument for aligning > > > with other tools is not as strong. > > > > > > In the meantime, I have adjusted my change locally to include AUIPC, and > > > written a substantive, and I hope, clear commit description. > > > If you would like me to resubmit a patch with this updated change, please > > > let me know. > > > > Since the patch is ready for posting, then it might as well be posted > > (even if it may not get merged right away). If the issue arises again, > > then we can refer to the latest proposed patch, which will be preserved > > in the mail archives. > > > > Thanks, > > drew > >