clang15/mips backend: failed to perform tail call elimination on a call site marked musttail

[kraj]

clang crashed with the attached testcase from grpcio-tools on mips

1.      <eof> parser at end of file
2.      Code generation
3.      Running pass 'Function Pass Manager' on module 'third_party/protobuf/src/google/protobuf/generated_message_tctable_lite.cc'.
4.      Running pass 'MIPS DAG->DAG Pattern Instruction Selection' on function '@_ZN6google8protobuf8internal8TcParser13SingularFixedIyhEEPKcPNS0_11MessageLiteES5_PNS1_12ParseContextEPKNS1_16TcParseTableBaseEyNS1_11TcFieldDataE'
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):

generated_message_tctable_lite-9b6bf4.tar.gz

[llvmbot]

@llvm/issue-subscribers-backend-mips

[kraj]

a workaround for now is to disable musttail attribute usage in grpcio-tools

[icepic]

I see that while compiling protobuf on MIPS64/OpenBSD too.

fatal error: error in backend: failed to perform tail call elimination on a call site marked musttail
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0.      Program arguments: /usr/bin/c++ -B /usr/ports/pobj/protobuf-3.21.12/bin -DHAVE_CONFIG_H -I. -I/usr/ports/pobj/protobuf-3.21.12/protobuf-3.21.12/src -I.. -pthread -DHAVE_PTHREAD=1 -DHAVE_ZLIB=1 -Wall -Wno-sign-compare -O2 -pipe -MT google/protobuf/generated_message_tctable_lite.lo -MD -MP -MF google/protobuf/.deps/generated_message_tctable_lite.Tpo -c /usr/ports/pobj/protobuf-3.21.12/protobuf-3.21.12/src/google/protobuf/generated_message_tctable_lite.cc -fPIC -DPIC -o google/protobuf/.libs/generated_message_tctable_lite.o
1.      <eof> parser at end of file
2.      Code generation
3.      Running pass 'Function Pass Manager' on module '/usr/ports/pobj/protobuf-3.21.12/protobuf-3.21.12/src/google/protobuf/generated_message_tctable_lite.cc'.
4.      Running pass 'MIPS DAG->DAG Pattern Instruction Selection' on function '@_ZN6google8protobuf8internal8TcParser9MiniParseEPNS0_11MessageLiteEPKcPNS1_12ParseContextEPKNS1_16TcParseTableBaseEyNS1_11TcFieldDataE'
c++: error: clang frontend command failed with exit code 70 (use -v to see invocation)
OpenBSD clang version 13.0.0
Target: mips64-unknown-openbsd7.2
Thread model: posix
InstalledDir: /usr/bin
c++: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
c++: note: diagnostic msg: /tmp/generated_message_tctable_lite-e5cce2.cpp
c++: note: diagnostic msg: /tmp/generated_message_tctable_lite-e5cce2.sh
c++: note: diagnostic msg: 

********************
Error while executing c++ -DHAVE_CONFIG_H -I. -I/usr/ports/pobj/protobuf-3.21.12/protobuf-3.21.12/src -I.. -pthread -DHAVE_PTHREAD=1 -DHAVE_ZLIB=1 -Wall -Wno-sign-compare -O2 -pipe -MT google/protobuf/generated_message_tctable_lite.lo -MD -MP -MF google/protobuf/.deps/generated_message_tctable_lite.Tpo -c /usr/ports/pobj/protobuf-3.21.12/protobuf-3.21.12/src/google/protobuf/generated_message_tctable_lite.cc -fPIC -DPIC -o google/protobuf/.libs/generated_message_tctable_lite.o

[InBetweenNames]

This can be worked around with -mllvm -mips-tail-calls=1, which seems to enable tail call optimization for MIPS in Clang. It appears this option is off by default at all optimization levels, but it is unclear why.

[brad0]

Please test.. #161860

[kraj]

Please test.. #161860

yes the above PR fixes this issue.

[icepic]

I tried to compile llvm from this branch, but I get stuck not being able to get llvm-project/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp compiled on my octeon. Took me a weekend to compile it all, except for the 47 targets that won't complete without it. [2/48] Building CXX object lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/LegalizerHelper.cpp.o FAILED: lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/LegalizerHelper.cpp.o /usr/bin/c++ -DEXPERIMENTAL_KEY_INSTRUCTIONS -DGTEST_HAS_RTTI=0 -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -D

…

__SHORT_FILE__=\"LegalizerHelper.cpp\" -I/usr/local/build-llvm/llvm-project/build/lib/CodeGen/GlobalISel -I/usr/local/build-llvm/llvm-pr oject/llvm/lib/CodeGen/GlobalISel -I/usr/local/build-llvm/llvm-project/build/include -I/usr/local/build-llvm/llvm-project/llvm/include -isystem /usr/local/include -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -std=c++17 -fno-exceptions -funwind-tables -fno-rtti -MD -MT lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/LegalizerHelper.cpp.o -MF lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/LegalizerHelper.cpp.o.d -o lib/CodeGen/GlobalISel/CMakeFiles/LLVMGlobalISel.dir/LegalizerHelper.cpp.o -c /usr/local/build-llvm/llvm-project/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp c++: *error: **clang frontend command failed with exit code 139 (use -v to see invocation)* OpenBSD clang version 19.1.7 Target: mips64-unknown-openbsd7.7 Thread model: posix InstalledDir: /usr/bin c++: *note: *diagnostic msg: Den lör 4 okt. 2025 kl 14:08 skrev Brad Smith ***@***.***>:

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