[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #20 from Jim Wilson --- Thanks for confirming that it solves the buildroot build problem. My gcc mainline g++ test failure turned out to be a thread related issue with qemu cross testing. The testcase works always on hardware, but fails maybe 10-20% of the time when run under qemu. RISC-V qemu is known to still have a few bugs in this area, though they might already be fixed in newer qemu versions than what I have.
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 Jim Wilson changed: What|Removed |Added Status|NEW |RESOLVED Resolution|--- |FIXED --- Comment #19 from Jim Wilson --- Patch applied to mainline. This is just a minor optimization for gcc-10 as a combiner patch between gcc-8 and gcc-9 reduces register pressure enough to prevent the hang. Hence there is no real need for the patch in gcc-9. The patch might be useful in gcc-8, but the problem is hard to reproduce, buildroot is the only one that ran into the problem, and they can always add the patch to their tree, so not clear if we really need it on the gcc-8 branch.
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #18 from CVS Commits --- The master branch has been updated by Jim Wilson : https://gcc.gnu.org/g:b780f68e025b2cf5631183e199ebf672ea463af6 commit r10-6528-gb780f68e025b2cf5631183e199ebf672ea463af6 Author: Jim Wilson Date: Sat Feb 8 13:57:36 2020 -0800 RISC-V: Improve caller-save code generation. Avoid paradoxical subregs when caller save. This reduces stack frame size due to smaller loads and stores, and more frequent rematerialization. PR target/93532 * config/riscv/riscv.h (HARD_REGNO_CALLER_SAVE_MODE): Define.
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #17 from Giulio Benetti --- (In reply to Andrew Pinski from comment #16) > (In reply to Giulio Benetti from comment #15) > > I mark this bug as resolved by: > > https://gcc.gnu.org/bugzilla/attachment.cgi?id=47794 > > The patch has not been applied to the sources yet. Oops, sorry, I'm not very used to bugzilla/gcc. Thanks again, for providing that patch.
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 Andrew Pinski changed: What|Removed |Added Status|RESOLVED|NEW Resolution|FIXED |--- --- Comment #16 from Andrew Pinski --- (In reply to Giulio Benetti from comment #15) > I mark this bug as resolved by: > https://gcc.gnu.org/bugzilla/attachment.cgi?id=47794 The patch has not been applied to the sources yet.
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 Giulio Benetti changed: What|Removed |Added Status|NEW |RESOLVED Resolution|--- |FIXED --- Comment #15 from Giulio Benetti --- I mark this bug as resolved by: https://gcc.gnu.org/bugzilla/attachment.cgi?id=47794
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #14 from Giulio Benetti --- Hi Ji, thanks for providing this patch, it fixes the problem.
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 Jim Wilson changed: What|Removed |Added Assignee|unassigned at gcc dot gnu.org |wilson at gcc dot gnu.org --- Comment #13 from Jim Wilson --- Created attachment 47794 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47794=edit untested patch to fix the problem
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #12 from Jim Wilson --- A bisection on mainline between the gcc-8 and gcc-9 releases shows that this testcase was fixed by a combine patch for PR87600 that stops combining hard regs with pseudos to reduce register pressure. The commentary refers to ira and lra problems. A combine patch won't be as safe as a RISC-V backend patch though. I tried testing the riscv HARD_REGNO_CALLER_SAVE_MODE patch with buildroot but it turns out that it is downloading a pre-built compiler instead of building one. So dropping in the patch doesn't do anything. I will have to figure out what is going on there. Trying the riscv patch with mainline on the testcase, I see that I get better rematerialization without the confusing subregs, and I also get smaller stack frames since we are saving SFmode now to the stack instead of DFmode now. Otherwise, I don't see any significant changes to the code. I tried a make check with the riscv patch on mainline, and got an unexpected g++ testsuite failure, so I will have to look into that.
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #11 from Jim Wilson --- I'm able to reproduce with the gcc-8-branch now. Maybe I made a mistake with my earlier build. Anyways, it looks like it is going wrong here in the reload dump Creating newreg=1856, assigning class NO_REGS to save r1856 434: fa0:SF=call [`sqrtf'] argc:0 REG_UNUSED fa0:SF REG_CALL_DECL `sqrtf' REG_EH_REGION 0 Add reg<-save after: 2446: r114:SF#0=r1856:DF 432: NOTE_INSN_BASIC_BLOCK 24 Add save<-reg after: 2445: r1856:DF=r114:SF#0 then later we appear to end up in a loop generating secondary reloads that need secondary reloads themselves, and so forth. The instruction above looks funny, trying to use a subreg to convert DFmode to SFmode. I don't think we should be generating that. So it looks like a caller save problem. If I add -fno-caller-saves the compile finishes. It appears that we need a definition for HARD_REGNO_CALLER_SAVE_MODE because the default definition can't work here. The comment in sparc.h for HARD_REGNO_CALLER_SAVE_MODE looks relevant. The same definition may work for RISC-V. Looks like the MIPS port does it the same way too.
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 Richard Biener changed: What|Removed |Added Status|WAITING |NEW
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #10 from Jim Wilson --- Created attachment 47774 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47774=edit testcase that reproduces for me compile with -O2 -fPIC -fstack-protector-strong
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 Jim Wilson changed: What|Removed |Added CC||wilson at gcc dot gnu.org --- Comment #9 from Jim Wilson --- I tried the buildroot instructions. It didn't work on an ubuntu 16.04 server machine. There is a 'python3 pip3 -q docwriter' command that hangs. I also discovered that the script isn't restartable. It runs -rf on the build directory and exits with an error. I did get it to work on my ubuntu 18.04 laptop. And it does hang, but it isn't the btPolyhedralContactClipping.cpp file that hangs for me, it is the btBoxBoxDetector.cpp file. I was able to reproduce this with a gcc-8.3.0 build using -O2 -fPIC -fstack-protector-strong options to compile the file. It does not reproduce using the top of the gcc-8-branch svn tree, suggesting that either it is already fixed, or it is maybe a memory corruption problem that is hard to reproduce. Using gdb to attach to the gcc-8.3.0 compiler, I see that it is looping in lra, but I haven't tried to debug that yet. #0 0x00705e7b in bitmap_find_bit (bit=42321, bit@entry=330, head=0x376ae88) at ../../gcc-8.3.0/gcc/bitmap.c:539 #1 bitmap_set_bit (head=0x376ae88, bit=bit@entry=42321) at ../../gcc-8.3.0/gcc/bitmap.c:600 #2 0x0099b95f in mark_regno_dead (regno=42321, mode=, point=) at ../../gcc-8.3.0/gcc/lra-lives.c:362 #3 0x0099c9c4 in process_bb_lives (dead_insn_p=false, curr_point=@0x7ffc9a90: 181876, bb=) at ../../gcc-8.3.0/gcc/lra-lives.c:842 #4 lra_create_live_ranges_1 (all_p=all_p@entry=true, dead_insn_p=dead_insn_p@entry=false) at ../../gcc-8.3.0/gcc/lra-lives.c:1337 #5 0x0099e7c0 in lra_create_live_ranges (all_p=all_p@entry=true, dead_insn_p=dead_insn_p@entry=false) at ../../gcc-8.3.0/gcc/lra-lives.c:1406 #6 0x00982d0c in lra (f=) at ../../gcc-8.3.0/gcc/lra.c:2473 #7 0x0093fa32 in do_reload () at ../../gcc-8.3.0/gcc/ira.c:5465 #8 (anonymous namespace)::pass_reload::execute (this=) at ../../gcc-8.3.0/gcc/ira.c:5649 ...
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #8 from Giulio Benetti --- Do you mind to use official Buildroot script to reproduce? Here is the procedure: # git clone git://git.busybox.net/buildroot # wget https://git.busybox.net/buildroot-test/tree/utils/br-reproduce-build - modify BASE_GIT=... with your buildroot path in br-reproduce-build then: # chmod a+x br-reproduce-build # ./br-reproduce-build 9a405ec6fabfa306c14a671a5e09359ac623c25b and wait until it hangs, otherwise I see it difficult to reproduce it. Is it ok for you?
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 Jakub Jelinek changed: What|Removed |Added CC||jakub at gcc dot gnu.org --- Comment #7 from Jakub Jelinek --- Can't reproduce, neither with 8.3.1 20200111 nor current trunk, it compiles pretty much instantly (cross-compiler from x86_64-linux to riscv32-linux).
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #6 from Giulio Benetti --- And this is how riscv32 gcc has been configured: Using built-in specs. COLLECT_GCC=/home/giuliobenetti/br_reproduce/9a405ec6fabfa306c14a671a5e09359ac623c25b/output/host/opt/ext-toolchain/bin/riscv32-buildroot-linux-gnu-gcc.br_real COLLECT_LTO_WRAPPER=/home/giuliobenetti/br_reproduce/9a405ec6fabfa306c14a671a5e09359ac623c25b/output/host/opt/ext-toolchain/bin/../libexec/gcc/riscv32-buildroot-linux-gnu/8.3.0/lto-wrapper Target: riscv32-buildroot-linux-gnu Configured with: ./configure --prefix=/opt/br-riscv32-glibc-2019.11 --sysconfdir=/opt/br-riscv32-glibc-2019.11/etc --enable-static --target=riscv32-buildroot-linux-gnu --with-sysroot=/opt/br-riscv32-glibc-2019.11/riscv32-buildroot-linux-gnu/sysroot --enable-__cxa_atexit --with-gnu-ld --disable-libssp --disable-multilib --disable-decimal-float --with-gmp=/opt/br-riscv32-glibc-2019.11 --with-mpc=/opt/br-riscv32-glibc-2019.11 --with-mpfr=/opt/br-riscv32-glibc-2019.11 --with-pkgversion='Buildroot 2019.11' --with-bugurl=http://bugs.buildroot.net/ --disable-libquadmath --enable-tls --enable-threads --without-isl --without-cloog --with-arch=rv32imafd --with-abi=ilp32d --enable-languages=c,c++ --with-build-time-tools=/opt/br-riscv32-glibc-2019.11/riscv32-buildroot-linux-gnu/bin --enable-shared --disable-libgomp Thread model: posix gcc version 8.3.0 (Buildroot 2019.11)
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #5 from Giulio Benetti --- Here is the specific command line which compiles .cpp file: /home/giuliobenetti/br_reproduce/9a405ec6fabfa306c14a671a5e09359ac623c25b/output/host/bin/riscv32-linux-g++ --sysroot=/home/giuliobenetti/br_reproduce/9a405ec6fabfa306c14a671a5e09359ac623c25b/output/host/riscv32-buildroot-linux-gnu/sysroot -DBT_USE_EGL -DBulletCollision_EXPORTS -DNO_OPENGL3 -DUSE_GRAPHICAL_BENCHMARK -I/home/giuliobenetti/br_reproduce/9a405ec6fabfa306c14a671a5e09359ac623c25b/output/build/bullet-2.89/src -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -O2 -save-temps -DNDEBUG -fPIC -o CMakeFiles/BulletCollision.dir/NarrowPhaseCollision/btPolyhedralContactClipping.o -c /home/giuliobenetti/br_reproduce/9a405ec6fabfa306c14a671a5e09359ac623c25b/output/build/bullet-2.89/src/BulletCollision/NarrowPhaseCollision/btPolyhedralContactClipping.cpp then it sits there forever.
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #4 from Giulio Benetti --- Created attachment 47769 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=47769=edit .ii of file where gcc hangs on building This is the .ii of file where gcc hangs on building.
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 Andrew Pinski changed: What|Removed |Added Status|UNCONFIRMED |WAITING Last reconfirmed||2020-02-01 Ever confirmed|0 |1 --- Comment #3 from Andrew Pinski --- Can you read https://gcc.gnu.org/bugs/ and provide the needed information?
[Bug target/93532] RISCV g++ hangs with optimization >= -O2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93532 --- Comment #2 from Giulio Benetti --- Sorry for the noise. This is true when compiling c files too. :-)
