[LLHDToLLVM] Signals declared in llhd.proc are never initialized thus leading to simulator crash

[maerhart]

In 5592ee2471aa57661ac76336d60b872ed06a70e5 support for llhd.sig inside llhd.proc was added. However, in LLHDToLLVM signals declared inside procs are never initialized. For entities this happens here.

As a result, the simulator crashes when attempting to drive this signal.

An example stack trace:

llhd-sim: /home/merhart/circt/llvm/llvm/include/llvm/ADT/SmallVector.h:273: llvm::SmallVectorTemplateCommon::reference llvm::SmallVectorTemplateCommon<circt::llhd::sim::Signal>::operator[](llvm::SmallVectorTemplateCommon::size_type) [T = circt::llhd::sim::Signal]: Assertion `idx < size()' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: /home/merhart/circt/build/bin/llhd-sim /home/merhart/circt/test/Dialect/LLHD/Simulator/sim_sig_in_proc.mlir -n 10 -r Foo -shared-libs=/home/merhart/circt/build/lib/libcirct-llhd-signals-runtime-wrappers.so
 #0 0x00007f376c0d887a llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /home/merhart/circt/llvm/llvm/lib/Support/Unix/Signals.inc:569:11
 #1 0x00007f376c0d8a2b PrintStackTraceSignalHandler(void*) /home/merhart/circt/llvm/llvm/lib/Support/Unix/Signals.inc:636:1
 #2 0x00007f376c0d70a6 llvm::sys::RunSignalHandlers() /home/merhart/circt/llvm/llvm/lib/Support/Signals.cpp:103:5
 #3 0x00007f376c0d9155 SignalHandler(int) /home/merhart/circt/llvm/llvm/lib/Support/Unix/Signals.inc:407:1
 #4 0x00007f376c26e1f0 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x141f0)
 #5 0x00007f376ba77fbb raise ./signal/../sysdeps/unix/sysv/linux/raise.c:50:1
 #6 0x00007f376ba5d864 abort ./stdlib/abort.c:81:7
 #7 0x00007f376ba5d749 get_sysdep_segment_value ./intl/loadmsgcat.c:509:8
 #8 0x00007f376ba5d749 _nl_load_domain ./intl/loadmsgcat.c:970:34
 #9 0x00007f376ba6f3d6 (/lib/x86_64-linux-gnu/libc.so.6+0x383d6)
#10 0x00007f376c08b599 llvm::SmallVectorTemplateCommon<circt::llhd::sim::Signal, void>::operator[](unsigned long) /home/merhart/circt/llvm/llvm/include/llvm/ADT/SmallVector.h:0:5
#11 0x00007f376c08b2ab driveSignal /home/merhart/circt/lib/Dialect/LLHD/Simulator/signals-runtime-wrappers.cpp:64:24
#12 0x00007f376c2840cd
#13 0x00000000006dc046 circt::llhd::sim::Engine::simulate(int, unsigned long) /home/merhart/circt/lib/Dialect/LLHD/Simulator/Engine.cpp:202:5
#14 0x000000000046ca71 main /home/merhart/circt/tools/llhd-sim/llhd-sim.cpp:221:3
#15 0x00007f376ba5f565 __libc_start_main ./csu/../csu/libc-start.c:332:16
#16 0x000000000046c41e _start (/home/merhart/circt/build/bin/llhd-sim+0x46c41e)
FileCheck error: '<stdin>' is empty.
FileCheck command line:  /home/merhart/circt/llvm/build/bin/FileCheck /home/merhart/circt/test/Dialect/LLHD/Simulator/sim_sig_in_proc.mlir