On Sun, Dec 15, 2019 at 09:43:20AM -0800, Ian Lance Taylor wrote: > On Sat, Dec 14, 2019 at 11:25 PM Segher Boessenkool > <seg...@kernel.crashing.org> wrote: > > > > On Sat, Dec 14, 2019 at 10:51:50AM -0800, Ian Lance Taylor via gcc wrote: > > > I'm seeing compiler crashes building libgcc for powerpc64le-linux-gnu, > > > cross-compiling from x86_64-pc-linux-gnu. I'm at SVN revision 279830. > > > I'm seeing the following. Is anybody else seeing this crash? Thanks. > > > > No, and that makes me wonder what is going on. The error is simple enough > > of course, as you note in a later message; but why do we not see it on > > every other build? > > I think it's because clang treats a left shift by a negative number as > undefined behavior but GCC does not. So GCC is consistently producing > some number, and clang is producing different numbers.
Hrm. Why did that not show up with ubsan then though? (Or maybe it did, and I just never heard). > I should note that I don't really understand what purpose that > constant is serving anyhow. - "operands[2] = GEN_INT (1 << (75 - REGNO (operands[0])));") + "operands[2] = GEN_INT (1 << (7 - (REGNO (operands[0]) - CR0_REGNO)));") The constant is the bitmask of which CR fields to save/restore (always one here, but the insn allows any combination). Committing that patch later today. Thanks for the report! Segher
