libdispatch compiled without frame pointers in at least in Swift 6.2, 6.1 and 6.0 on x86_64

[weissi]

It appears that Swift on Linux is still compiling without frame pointers in 6.0, 6.1 and 6.2. The official docker images for for example Ubuntu 24.04 (noble) on x86_64 have this code:

Expected:
has pushq %rbp; movq %rsp, %rbp

Actual:
hasn't got push rbp; mov rsp,rbp

One-line repro from nothing: docker run -it --rm --platform linux/amd64 swift:6.2-noble lldb --batch -o 'dis -n _dispatch_sema4_wait' /usr/lib/swift/linux/libdispatch.so

(lldb) target create "/usr/lib/swift/linux/libdispatch.so"
Current executable set to '/usr/lib/swift/linux/libdispatch.so' (x86_64).
(lldb) dis -n _dispatch_sema4_wait
libdispatch.so`_dispatch_sema4_wait:
libdispatch.so[0x3c580] <+0>:  pushq  %rbx
libdispatch.so[0x3c581] <+1>:  movq   %rdi, %rbx
libdispatch.so[0x3c584] <+4>:  nopw   %cs:(%rax,%rax)
libdispatch.so[0x3c590] <+16>: movq   %rbx, %rdi
libdispatch.so[0x3c593] <+19>: callq  0x1f410        ; symbol stub for: sem_wait
libdispatch.so[0x3c598] <+24>: cmpl   $-0x1, %eax
libdispatch.so[0x3c59b] <+27>: jne    0x3c5ac        ; <+44>
libdispatch.so[0x3c59d] <+29>: callq  0x1ee20        ; symbol stub for: __errno_location
libdispatch.so[0x3c5a2] <+34>: cmpl   $0x4, (%rax)
libdispatch.so[0x3c5a5] <+37>: je     0x3c590        ; <+16>
libdispatch.so[0x3c5a7] <+39>: callq  0x22c70        ; _dispatch_sema4_wait.cold.1
libdispatch.so[0x3c5ac] <+44>: popq   %rbx
libdispatch.so[0x3c5ad] <+45>: retq   

Same for the Swift overlay :(

No rbp pushing

(lldb) dis -n 'Dispatch.DispatchSemaphore.wait'
libswiftDispatch.so`wait:
libswiftDispatch.so[0x19120] <+0>: jmp    0x190b0        ; Dispatch.DispatchSemaphore.wait(wallTimeout: Dispatch.DispatchWallTime) -> Dispatch.DispatchTimeoutResult

libswiftDispatch.so`wait:
libswiftDispatch.so[0x190b0] <+0>:  pushq  %rax
libswiftDispatch.so[0x190b1] <+1>:  movq   %rdi, %rsi
libswiftDispatch.so[0x190b4] <+4>:  movq   0x10(%r13), %rdi
libswiftDispatch.so[0x190b8] <+8>:  callq  0x14ca0        ; symbol stub for: dispatch_semaphore_wait
libswiftDispatch.so[0x190bd] <+13>: testq  %rax, %rax
libswiftDispatch.so[0x190c0] <+16>: setne  %al
libswiftDispatch.so[0x190c3] <+19>: popq   %rcx
libswiftDispatch.so[0x190c4] <+20>: retq   

libswiftDispatch.so`wait:
libswiftDispatch.so[0x190a0] <+0>:  movq   0x10(%r13), %rdi
libswiftDispatch.so[0x190a4] <+4>:  movq   $-0x1, %rsi
libswiftDispatch.so[0x190ab] <+11>: jmp    0x14ca0        ; symbol stub for: dispatch_semaphore_wait

running the one-line repro:

$ docker run -it --rm --platform linux/amd64 swift:6.2-noble lldb --batch -o 'dis -n _dispatch_sema4_wait' /usr/lib/swift/linux/libdispatch.so
lldb[1]: ==== LLDB swift-healthcheck log. ===
This file contains the configuration of LLDB's embedded Swift compiler to help diagnosing module import and search path issues. The swift-healthcheck command is meant to be run *after* an error has occurred.
lldb version 17.0.0 (https://github.com/swiftlang/llvm-project.git revision f403f1080b28ed3bf592ccbc491dadda2a5d4814)
Swift version 6.2 (swift-6.2-RELEASE)

(lldb) target create "/usr/lib/swift/linux/libdispatch.so"
Current executable set to '/usr/lib/swift/linux/libdispatch.so' (x86_64).
(lldb) dis -n _dispatch_sema4_wait
libdispatch.so`_dispatch_sema4_wait:
libdispatch.so[0x3c580] <+0>:  pushq  %rbx
libdispatch.so[0x3c581] <+1>:  movq   %rdi, %rbx
libdispatch.so[0x3c584] <+4>:  nopw   %cs:(%rax,%rax)
libdispatch.so[0x3c590] <+16>: movq   %rbx, %rdi
libdispatch.so[0x3c593] <+19>: callq  0x1f410        ; symbol stub for: sem_wait
libdispatch.so[0x3c598] <+24>: cmpl   $-0x1, %eax
libdispatch.so[0x3c59b] <+27>: jne    0x3c5ac        ; <+44>
libdispatch.so[0x3c59d] <+29>: callq  0x1ee20        ; symbol stub for: __errno_location
libdispatch.so[0x3c5a2] <+34>: cmpl   $0x4, (%rax)
libdispatch.so[0x3c5a5] <+37>: je     0x3c590        ; <+16>
libdispatch.so[0x3c5a7] <+39>: callq  0x22c70        ; _dispatch_sema4_wait.cold.1
libdispatch.so[0x3c5ac] <+44>: popq   %rbx
libdispatch.so[0x3c5ad] <+45>: retq   

[weissi]

Apple folks, this is rdar://160759746

[akmorrison]

We pass momit-leaf-frame-pointer when it’s available:

swift-corelibs-libdispatch/src/CMakeLists.txt

Line 145 in 0bb6c10

target_compile_options(dispatch PRIVATE -momit-leaf-frame-pointer)

I wouldn’t expect this to cause frames to be omitted in sema4_wait (or the swiftoverlay version) since they aren’t leaf frames - maybe we’re getting this from the toolchain as a default somehow, or the compiler assumes no frames if the only option given is the leaf frame one