[llvm] [InstCombine] Drop NSW when converting `shl X, BW - 1` back into mul (PR #121633)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-debian-cpp20` running on `clang-debian-cpp20` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/108/builds/7725

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_32.s' FAILED ********************
Exit Code: 134

Command Output (stderr):
--
RUN: at line 1: /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-mc -triple=x86_64-unknown-linux -position-independent      -filetype=obj -o /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/test/ExecutionEngine/JITLink/x86-64/Output/ELF_R_X86_64_32.s.tmp.o /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_32.s
+ /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-mc -triple=x86_64-unknown-linux -position-independent -filetype=obj -o /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/test/ExecutionEngine/JITLink/x86-64/Output/ELF_R_X86_64_32.s.tmp.o /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_32.s
RUN: at line 3: /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink -noexec -abs X=0x12345678 -check=/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_32.s /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/test/ExecutionEngine/JITLink/x86-64/Output/ELF_R_X86_64_32.s.tmp.o
+ /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink -noexec -abs X=0x12345678 -check=/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_32.s /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/test/ExecutionEngine/JITLink/x86-64/Output/ELF_R_X86_64_32.s.tmp.o
llvm-jitlink error: Resource tracker 0x5d4be1fad1b0 became defunct
llvm-jitlink: /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/include/llvm/ExecutionEngine/Orc/SymbolStringPool.h:285: llvm::orc::SymbolStringPool::~SymbolStringPool(): Assertion `Pool.empty() && "Dangling references at pool destruction time"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.	Program arguments: /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink -noexec -abs X=0x12345678 -check=/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_32.s /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/test/ExecutionEngine/JITLink/x86-64/Output/ELF_R_X86_64_32.s.tmp.o
 #0 0x00005d4bddcb8b98 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink+0xeb5b98)
 #1 0x00005d4bddcb668d llvm::sys::RunSignalHandlers() (/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink+0xeb368d)
 #2 0x00005d4bddcb9138 SignalHandler(int) Signals.cpp:0:0
 #3 0x00007ce5d2a1b510 (/lib/x86_64-linux-gnu/libc.so.6+0x3c510)
 #4 0x00007ce5d2a690fc (/lib/x86_64-linux-gnu/libc.so.6+0x8a0fc)
 #5 0x00007ce5d2a1b472 raise (/lib/x86_64-linux-gnu/libc.so.6+0x3c472)
 #6 0x00007ce5d2a054b2 abort (/lib/x86_64-linux-gnu/libc.so.6+0x264b2)
 #7 0x00007ce5d2a053d5 (/lib/x86_64-linux-gnu/libc.so.6+0x263d5)
 #8 0x00007ce5d2a143a2 (/lib/x86_64-linux-gnu/libc.so.6+0x353a2)
 #9 0x00005d4bdd551f0c (/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink+0x74ef0c)
#10 0x00005d4bddb9bb37 llvm::orc::ExecutorProcessControl::~ExecutorProcessControl() (/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink+0xd98b37)
#11 0x00005d4bddb9d27f llvm::orc::SelfExecutorProcessControl::~SelfExecutorProcessControl() (/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink+0xd9a27f)
#12 0x00005d4bddacee88 llvm::orc::ExecutionSession::~ExecutionSession() (/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink+0xccbe88)
#13 0x00005d4bdd52aedd llvm::Session::~Session() (/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink+0x727edd)
#14 0x00005d4bdd535664 main (/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink+0x732664)
#15 0x00007ce5d2a066ca (/lib/x86_64-linux-gnu/libc.so.6+0x276ca)
#16 0x00007ce5d2a06785 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x27785)
#17 0x00005d4bdd523671 _start (/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink+0x720671)
/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/test/ExecutionEngine/JITLink/x86-64/Output/ELF_R_X86_64_32.s.script: line 3: 1365555 Aborted                 /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/llvm-jitlink -noexec -abs X=0x12345678 -check=/vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/ExecutionEngine/JITLink/x86-64/ELF_R_X86_64_32.s /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/test/ExecutionEngine/JITLink/x86-64/Output/ELF_R_X86_64_32.s.tmp.o

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/121633