PR for llvm/llvm-project#53592 #5
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(cherry picked from commit 1eb4f88)
As discussed in D118534, all of the recent AMD CPUs have relatively fast (<14 cycle latency) "sqrtss" and "sqrtps" instructions: https://uops.info/table.html?search=sqrtps&cb_lat=on&cb_tp=on&cb_SNB=on&cb_SKL=on&cb_ZENp=on&cb_ZEN2=on&cb_ZEN3=on&cb_measurements=on&cb_avx=on&cb_sse=on So we should set this tuning flag to alter codegen of plain "sqrt(X)" expansion (as opposed to reciprocal-sqrt - there is other test coverage for that pattern). The expansion is both slower and less accurate than the hardware instruction. Differential Revision: https://reviews.llvm.org/D119001 (cherry picked from commit fff3e1d)
llvmbot
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Feb 10, 2022
We experienced some deadlocks when we used multiple threads for logging using `scan-builds` intercept-build tool when we used multiple threads by e.g. logging `make -j16` ``` (gdb) bt #0 0x00007f2bb3aff110 in __lll_lock_wait () from /lib/x86_64-linux-gnu/libpthread.so.0 #1 0x00007f2bb3af70a3 in pthread_mutex_lock () from /lib/x86_64-linux-gnu/libpthread.so.0 #2 0x00007f2bb3d152e4 in ?? () #3 0x00007ffcc5f0cc80 in ?? () #4 0x00007f2bb3d2bf5b in ?? () from /lib64/ld-linux-x86-64.so.2 #5 0x00007f2bb3b5da27 in ?? () from /lib/x86_64-linux-gnu/libc.so.6 #6 0x00007f2bb3b5dbe0 in exit () from /lib/x86_64-linux-gnu/libc.so.6 #7 0x00007f2bb3d144ee in ?? () #8 0x746e692f706d742f in ?? () #9 0x692d747065637265 in ?? () #10 0x2f653631326b3034 in ?? () #11 0x646d632e35353532 in ?? () #12 0x0000000000000000 in ?? () ``` I think the gcc's exit call caused the injected `libear.so` to be unloaded by the `ld`, which in turn called the `void on_unload() __attribute__((destructor))`. That tried to acquire an already locked mutex which was left locked in the `bear_report_call()` call, that probably encountered some error and returned early when it forgot to unlock the mutex. All of these are speculation since from the backtrace I could not verify if frames 2 and 3 are in fact corresponding to the `libear.so` module. But I think it's a fairly safe bet. So, hereby I'm releasing the held mutex on *all paths*, even if some failure happens. PS: I would use lock_guards, but it's C. Reviewed-by: NoQ Differential Revision: https://reviews.llvm.org/D118439 (cherry picked from commit d919d02)
tstellar
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Feb 14, 2022
We experienced some deadlocks when we used multiple threads for logging using `scan-builds` intercept-build tool when we used multiple threads by e.g. logging `make -j16` ``` (gdb) bt #0 0x00007f2bb3aff110 in __lll_lock_wait () from /lib/x86_64-linux-gnu/libpthread.so.0 #1 0x00007f2bb3af70a3 in pthread_mutex_lock () from /lib/x86_64-linux-gnu/libpthread.so.0 #2 0x00007f2bb3d152e4 in ?? () #3 0x00007ffcc5f0cc80 in ?? () #4 0x00007f2bb3d2bf5b in ?? () from /lib64/ld-linux-x86-64.so.2 #5 0x00007f2bb3b5da27 in ?? () from /lib/x86_64-linux-gnu/libc.so.6 #6 0x00007f2bb3b5dbe0 in exit () from /lib/x86_64-linux-gnu/libc.so.6 #7 0x00007f2bb3d144ee in ?? () #8 0x746e692f706d742f in ?? () #9 0x692d747065637265 in ?? () #10 0x2f653631326b3034 in ?? () #11 0x646d632e35353532 in ?? () #12 0x0000000000000000 in ?? () ``` I think the gcc's exit call caused the injected `libear.so` to be unloaded by the `ld`, which in turn called the `void on_unload() __attribute__((destructor))`. That tried to acquire an already locked mutex which was left locked in the `bear_report_call()` call, that probably encountered some error and returned early when it forgot to unlock the mutex. All of these are speculation since from the backtrace I could not verify if frames 2 and 3 are in fact corresponding to the `libear.so` module. But I think it's a fairly safe bet. So, hereby I'm releasing the held mutex on *all paths*, even if some failure happens. PS: I would use lock_guards, but it's C. Reviewed-by: NoQ Differential Revision: https://reviews.llvm.org/D118439 (cherry picked from commit d919d02)
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resolves llvm#53592