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MBkkt
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…erver (llvm#148774) Summary: There was a deadlock was introduced by [PR llvm#146441](llvm#146441) which changed `CurrentThreadIsPrivateStateThread()` to `CurrentThreadPosesAsPrivateStateThread()`. This change caused the execution path in [`ExecutionContextRef::SetTargetPtr()`](https://github.com/llvm/llvm-project/blob/10b5558b61baab59c7d3dff37ffdf0861c0cc67a/lldb/source/Target/ExecutionContext.cpp#L513) to now enter a code block that was previously skipped, triggering [`GetSelectedFrame()`](https://github.com/llvm/llvm-project/blob/10b5558b61baab59c7d3dff37ffdf0861c0cc67a/lldb/source/Target/ExecutionContext.cpp#L522) which leads to a deadlock. Thread 1 gets m_modules_mutex in [`ModuleList::AppendImpl`](https://github.com/llvm/llvm-project/blob/96148f92146e5211685246722664e51ec730e7ba/lldb/source/Core/ModuleList.cpp#L218), Thread 3 gets m_language_runtimes_mutex in [`GetLanguageRuntime`](https://github.com/llvm/llvm-project/blob/96148f92146e5211685246722664e51ec730e7ba/lldb/source/Target/Process.cpp#L1501), but then Thread 1 waits for m_language_runtimes_mutex in [`GetLanguageRuntime`](https://github.com/llvm/llvm-project/blob/96148f92146e5211685246722664e51ec730e7ba/lldb/source/Target/Process.cpp#L1501) while Thread 3 waits for m_modules_mutex in [`ScanForGNUstepObjCLibraryCandidate`](https://github.com/llvm/llvm-project/blob/96148f92146e5211685246722664e51ec730e7ba/lldb/source/Plugins/LanguageRuntime/ObjC/GNUstepObjCRuntime/GNUstepObjCRuntime.cpp#L57). This fixes the deadlock by adding a scoped block around the mutex lock before the call to the notifier, and moved the notifier call outside of the mutex-guarded section. The notifier call [`NotifyModuleAdded`](https://github.com/llvm/llvm-project/blob/96148f92146e5211685246722664e51ec730e7ba/lldb/source/Target/Target.cpp#L1810) should be thread-safe, since the module should be added to the `ModuleList` before the mutex is released, and the notifier doesn't modify the module list further, and the call is operates on local state and the `Target` instance. ### Deadlocked Thread backtraces: ``` * thread llvm#3, name = 'dbg.evt-handler', stop reason = signal SIGSTOP * frame #0: 0x00007f2f1e2973dc libc.so.6`futex_wait(private=0, expected=2, futex_word=0x0000563786bd5f40) at futex-internal.h:146:13 /*... a bunch of mutex related bt ... */ liblldb.so.21.0git`std::lock_guard<std::recursive_mutex>::lock_guard(this=0x00007f2f0f1927b0, __m=0x0000563786bd5f40) at std_mutex.h:229:19 frame llvm#8: 0x00007f2f27946eb7 liblldb.so.21.0git`ScanForGNUstepObjCLibraryCandidate(modules=0x0000563786bd5f28, TT=0x0000563786bd5eb8) at GNUstepObjCRuntime.cpp:60:41 frame llvm#9: 0x00007f2f27946c80 liblldb.so.21.0git`lldb_private::GNUstepObjCRuntime::CreateInstance(process=0x0000563785e1d360, language=eLanguageTypeObjC) at GNUstepObjCRuntime.cpp:87:8 frame llvm#10: 0x00007f2f2746fca5 liblldb.so.21.0git`lldb_private::LanguageRuntime::FindPlugin(process=0x0000563785e1d360, language=eLanguageTypeObjC) at LanguageRuntime.cpp:210:36 frame llvm#11: 0x00007f2f2742c9e3 liblldb.so.21.0git`lldb_private::Process::GetLanguageRuntime(this=0x0000563785e1d360, language=eLanguageTypeObjC) at Process.cpp:1516:9 ... frame llvm#21: 0x00007f2f2750b5cc liblldb.so.21.0git`lldb_private::Thread::GetSelectedFrame(this=0x0000563785e064d0, select_most_relevant=DoNoSelectMostRelevantFrame) at Thread.cpp:274:48 frame llvm#22: 0x00007f2f273f9957 liblldb.so.21.0git`lldb_private::ExecutionContextRef::SetTargetPtr(this=0x00007f2f0f193778, target=0x0000563786bd5be0, adopt_selected=true) at ExecutionContext.cpp:525:32 frame llvm#23: 0x00007f2f273f9714 liblldb.so.21.0git`lldb_private::ExecutionContextRef::ExecutionContextRef(this=0x00007f2f0f193778, target=0x0000563786bd5be0, adopt_selected=true) at ExecutionContext.cpp:413:3 frame llvm#24: 0x00007f2f270e80af liblldb.so.21.0git`lldb_private::Debugger::GetSelectedExecutionContext(this=0x0000563785d83bc0) at Debugger.cpp:1225:23 frame llvm#25: 0x00007f2f271bb7fd liblldb.so.21.0git`lldb_private::Statusline::Redraw(this=0x0000563785d83f30, update=true) at Statusline.cpp:136:41 ... * thread #1, name = 'lldb', stop reason = signal SIGSTOP * frame #0: 0x00007f2f1e2973dc libc.so.6`futex_wait(private=0, expected=2, futex_word=0x0000563785e1dd98) at futex-internal.h:146:13 /*... a bunch of mutex related bt ... */ liblldb.so.21.0git`std::lock_guard<std::recursive_mutex>::lock_guard(this=0x00007ffe62be0488, __m=0x0000563785e1dd98) at std_mutex.h:229:19 frame llvm#8: 0x00007f2f2742c8d1 liblldb.so.21.0git`lldb_private::Process::GetLanguageRuntime(this=0x0000563785e1d360, language=eLanguageTypeC_plus_plus) at Process.cpp:1510:41 frame llvm#9: 0x00007f2f2743c46f liblldb.so.21.0git`lldb_private::Process::ModulesDidLoad(this=0x0000563785e1d360, module_list=0x00007ffe62be06a0) at Process.cpp:6082:36 ... frame llvm#13: 0x00007f2f2715cf03 liblldb.so.21.0git`lldb_private::ModuleList::AppendImpl(this=0x0000563786bd5f28, module_sp=ptr = 0x563785cec560, use_notifier=true) at ModuleList.cpp:246:19 frame llvm#14: 0x00007f2f2715cf4c liblldb.so.21.0git`lldb_private::ModuleList::Append(this=0x0000563786bd5f28, module_sp=ptr = 0x563785cec560, notify=true) at ModuleList.cpp:251:3 ... frame llvm#19: 0x00007f2f274349b3 liblldb.so.21.0git`lldb_private::Process::ConnectRemote(this=0x0000563785e1d360, remote_url=(Data = "connect://localhost:1234", Length = 24)) at Process.cpp:3250:9 frame llvm#20: 0x00007f2f27411e0e liblldb.so.21.0git`lldb_private::Platform::DoConnectProcess(this=0x0000563785c59990, connect_url=(Data = "connect://localhost:1234", Length = 24), plugin_name=(Data = "gdb-remote", Length = 10), debugger=0x0000563785d83bc0, stream=0x00007ffe62be3128, target=0x0000563786bd5be0, error=0x00007ffe62be1ca0) at Platform.cpp:1926:23 ``` ## Test Plan: Built a hello world a.out Run server in one terminal: ``` ~/llvm/build/Debug/bin/lldb-server g :1234 a.out ``` Run client in another terminal ``` ~/llvm/build/Debug/bin/lldb -o "gdb-remote 1234" -o "b hello.cc:3" ``` Before: Client hangs indefinitely ``` ~/llvm/build/Debug/bin/lldb -o "gdb-remote 1234" -o "b main" (lldb) gdb-remote 1234 ^C^C ``` After: ``` ~/llvm/build/Debug/bin/lldb -o "gdb-remote 1234" -o "b hello.cc:3" (lldb) gdb-remote 1234 Process 837068 stopped * thread #1, name = 'a.out', stop reason = signal SIGSTOP frame #0: 0x00007ffff7fe4a60 ld-linux-x86-64.so.2`_start: -> 0x7ffff7fe4a60 <+0>: movq %rsp, %rdi 0x7ffff7fe4a63 <+3>: callq 0x7ffff7fe5780 ; _dl_start at rtld.c:522:1 ld-linux-x86-64.so.2`_dl_start_user: 0x7ffff7fe4a68 <+0>: movq %rax, %r12 0x7ffff7fe4a6b <+3>: movl 0x18067(%rip), %eax ; _dl_skip_args (lldb) b hello.cc:3 Breakpoint 1: where = a.out`main + 15 at hello.cc:4:13, address = 0x00005555555551bf (lldb) c Process 837068 resuming Process 837068 stopped * thread #1, name = 'a.out', stop reason = breakpoint 1.1 frame #0: 0x00005555555551bf a.out`main at hello.cc:4:13 1 #include <iostream> 2 3 int main() { -> 4 std::cout << "Hello World" << std::endl; 5 return 0; 6 } ```
MBkkt
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Aug 13, 2025
…lvm#152156) With this new A320 in-order core, we follow adding the FeatureUseFixedOverScalableIfEqualCost feature to A510 and A520 (llvm#132246), which reaps the same code generation benefits of preferring fixed over scalable when the cost is equal. So when we have: ``` void foo(float* a, float* b, float* dst, unsigned n) { for (unsigned i = 0; i < n; ++i) dst[i] = a[i] + b[i]; } ``` When compiling without the feature enabled, we get: ``` ... ld1b { z0.b }, p0/z, [x0, x10] ld1b { z2.b }, p0/z, [x1, x10] add x12, x0, x10 ldr z1, [x12, #1, mul vl] add x12, x1, x10 ldr z3, [x12, #1, mul vl] fadd z0.s, z2.s, z0.s add x12, x2, x10 fadd z1.s, z3.s, z1.s dech x11 st1b { z0.b }, p0, [x2, x10] incb x10, all, mul llvm#2 str z1, [x12, #1, mul vl] ... ``` When compiling with, we get: ``` ... ldp q0, q1, [x12, #-16] ldp q2, q3, [x11, #-16] subs x13, x13, llvm#8 fadd v0.4s, v2.4s, v0.4s fadd v1.4s, v3.4s, v1.4s add x11, x11, llvm#32 add x12, x12, llvm#32 stp q0, q1, [x10, #-16] add x10, x10, llvm#32 ... ```
MBkkt
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that referenced
this pull request
Aug 13, 2025
M68k's SETCC instruction (`scc`) distinctly fills the destination byte
with all 1s. If boolean contents are set to `ZeroOrOneBooleanContent`,
LLVM can mistakenly think the destination holds `0x01` instead of `0xff`
and emit broken code as a result. This change corrects the boolean
content type to `ZeroOrNegativeOneBooleanContent`.
For example, this IR:
```llvm
define dso_local signext range(i8 0, 2) i8 @testBool(i32 noundef %a) local_unnamed_addr #0 {
entry:
%cmp = icmp eq i32 %a, 4660
%. = zext i1 %cmp to i8
ret i8 %.
}
```
would previously build as:
```asm
testBool: ; @testBool
cmpi.l llvm#4660, (4,%sp)
seq %d0
and.l llvm#255, %d0
rts
```
Notice the `zext` is erroneously not clearing the low bits, and thus the
register returns with 255 instead of 1. This patch fixes the issue:
```asm
testBool: ; @testBool
cmpi.l llvm#4660, (4,%sp)
seq %d0
and.l #1, %d0
rts
```
Most of the tests containing `scc` suffered from the same value error as
described above, so those tests have been updated to match the new
output (which also logically corrects them).
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