https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112415
--- Comment #15 from Manolis Tsamis <manolis.tsamis at vrull dot eu> --- (In reply to Sam James from comment #13) > Created attachment 56527 [details] > compile.c.323r.fold_mem_offsets.bad.xz > > Output from > ``` > hppa2.0-unknown-linux-gnu-gcc -c -DNDEBUG -g -fwrapv -O3 -Wall -O2 > -std=c11 -Werror=implicit-function-declaration -fvisibility=hidden > -I/home/sam/git/cpython/Include/internal -IObjects -IInclude -IPython -I. > -I/home/sam/git/cpython/Include -DPy_BUILD_CORE -o Python/compile.o > /home/sam/git/cpython/Python/compile.c -fdump-rtl-fold_mem_offsets-all > ``` > > If I instrument certain functions in compile.c with no optimisation > attribuet or build the file with -fno-fold-mem-offsets, Python works, so I'm > reasonably sure this is the relevant object. Thanks for the dump file! There are 66 folded/eliminated instructions in this object file; I did look at each case and there doesn't seem to be anything strange. In fact most of the transformations are straightforward: - All except a couple of cases don't involve any arithmetic, so it's just moving a constant around. - The majority of the transformations are 'trivial' and consist of a single add and then a memory operation: a sequence like X = Y + Const, R = MEM[X + 0] is folded to X = Y, R = MEM[X + Const]. I wonder why so many of these exist and are not optimized elsewhere. - There are some cases with negative offsets, but the calculations look correct. - There are few more complicated cases, but I've done these on paper and also look correct. Of course I could be missing some more complicated effect, but what I want to say is that everything looks sensible in this particular file. > Thanks! You are very welcome to have access to some HPPA machines for > this kind of work. Please email me an SSH public key + desired username > if that sounds helpful. Yes, since I couldn't find anything interesting in the dump, that would definitely be helpful. Thanks! Manolis
