Run do the command with -v -save-temps and then extract the lto1 line from the output and run that under the debugger.
First, run the tests normally:
cd build/build_sysroot/sysroot_src/library/stdarch/ STDARCH_TEST_EVERYTHING=1 CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_RUNNER="sde -future -rtm_mode full --" TARGET=x86_64-unknown-linux-gnu ../../../../../y.sh cargo test
It will show the command it ran, something like this:
process didn't exit successfully: sde -future -rtm_mode full -- /home/user/projects/rustc_codegen_gcc/build/build_sysroot/sysroot_src/library/stdarch/target/debug/deps/core_arch-fd2d75f89baae5c6 (signal: 11, SIGSEGV: invalid memory reference)
Then add the -debug flag to it:
sde -debug -future -rtm_mode full -- /home/user/projects/rustc_codegen_gcc/build/build_sysroot/sysroot_src/library/stdarch/target/debug/deps/core_arch-fd2d75f89baae5c6
To see the symbols in gdb, specify the executable in your command:
gdb /home/user/projects/rustc_codegen_gcc/build/build_sysroot/sysroot_src/library/stdarch/target/debug/deps/core_arch-fd2d75f89baae5c6
and then write the gdb command that sde tells you to use, something like: