[llvm-bugs] [Bug 46363] New: WebAssembly hangs on switch with __builtin_unreachable in default.

via llvm-bugs llvm-bugs at lists.llvm.org
Wed Jun 17 06:31:39 PDT 2020


            Bug ID: 46363
           Summary: WebAssembly hangs on switch with __builtin_unreachable
                    in default.
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: bungeman at gmail.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org,
                    neeilans at live.com, richard-llvm at metafoo.co.uk


$ emsdk/upstream/bin/clang-11 --version
clang version 11.0.0

$cat > repro.cpp <<EOF
int CToI(char c) {
    switch (c) {
        case 'r': return 0;
        case 'g': return 1;
        case 'b': return 2;
        case 'a': return 3;
        case '0': return 4;
        case '1': return 5;

$ emsdk/upstream/bin/clang-11 -cc1 -triple wasm32-unknown-emscripten -emit-obj
-disable-free -main-file-name repro.cpp -mrelocation-model static
-mframe-pointer=none -fno-rounding-math -mconstructor-aliases -target-cpu
generic -fvisibility hidden -dwarf-column-info -debugger-tuning=gdb -O3
-std=c++17 -nostdsysteminc -mllvm -combiner-global-alias-analysis=false -mllvm
-enable-emscripten-sjlj -mllvm -disable-lsr -o repro.o -x c++ repro.cpp

the clang-11 invocation will hang at any optimization level other than -O0.
This can also currently be reproduced on CompilerExplorer with the above code
with the "WebAssembly clang (trunk)" compiler and any optimization level over

This seems to be a fairly recent regression as this was known to work at some
point in the not too distant past (will attempt to bisect). Removing any of the
'case' statements seems to make it work, this seems to require at least six
cases to reproduce.

You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20200617/06d9555c/attachment.html>

More information about the llvm-bugs mailing list