NanoMips: div-rem optimization #2
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draganmladjenovic
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draganmladjenovic
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cme
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Mar 16, 2023
Disable expansion of mod to mul-and-sub when Os or Oz. Generate udivmoddi4 libcall when div-rem pairs of type uint64 are present.
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draganmladjenovic
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cme
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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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Change https://reviews.llvm.org/D140059 exposed the following crash in Z3Solver, where bit widths were not checked consistently with that change. This change makes the check consistent, and fixes the crash. ``` clang: <root>/llvm/include/llvm/ADT/APSInt.h:99: int64_t llvm::APSInt::getExtValue() const: Assertion `isRepresentableByInt64() && "Too many bits for int64_t"' failed. ... Stack dump: 0. Program arguments: clang -cc1 -internal-isystem <root>/lib/clang/16/include -nostdsysteminc -analyze -analyzer-checker=core,unix.Malloc,debug.ExprInspection -analyzer-config crosscheck-with-z3=true -verify reproducer.c #0 0x00000000045b3476 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) <root>/llvm/lib/Support/Unix/Signals.inc:567:22 #1 0x00000000045b3862 PrintStackTraceSignalHandler(void*) <root>/llvm/lib/Support/Unix/Signals.inc:641:1 #2 0x00000000045b14a5 llvm::sys::RunSignalHandlers() <root>/llvm/lib/Support/Signals.cpp:104:20 #3 0x00000000045b2eb4 SignalHandler(int) <root>/llvm/lib/Support/Unix/Signals.inc:412:1 ... #9 0x0000000004be2eb3 llvm::APSInt::getExtValue() const <root>/llvm/include/llvm/ADT/APSInt.h:99:5 <root>/llvm/lib/Support/Z3Solver.cpp:740:53 clang::ASTContext&, clang::ento::SymExpr const*, llvm::APSInt const&, llvm::APSInt const&, bool) <root>/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SMTConv.h:552:61 ``` Reviewed By: steakhal Differential Revision: https://reviews.llvm.org/D142627 (cherry picked from commit f027dd5)
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Disable expansion of mod to mul-and-sub when Os or Oz. Generate udivmoddi4 libcall when div-rem pairs of type uint64 are present.
This resolves the following issue: