[BOLT] [3.12] Python 3.12.7 --enable bolt option not working #124948
Comments
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cc @corona10 |
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I will take a look |
leesm@leesm-ubuntu ~/Workspace/cpython ./configure --enable-bolt
leesm@leesm-ubuntu ~/Workspace/cpython make
->
BOLT-INFO: basic block reordering modified layout of 2699 functions (68.73% of profiled, 45.13% of total)
BOLT-INFO: UCE removed 36 blocks and 0 bytes of code
BOLT-INFO: splitting separates 1220980 hot bytes from 780031 cold bytes (61.02% of split functions is hot).
BOLT-INFO: 43 Functions were reordered by LoopInversionPass
BOLT-INFO: program-wide dynostats after all optimizations before SCTC and FOP:
18740817903 : executed forward branches
7826248652 : taken forward branches
7349242935 : executed backward branches
2852718872 : taken backward branches
4004518103 : executed unconditional branches
3353239032 : all function calls
1262678534 : indirect calls
137784052 : PLT calls
259717127425 : executed instructions
77083459173 : executed load instructions
43910218984 : executed store instructions
4541628185 : taken jump table branches
0 : taken unknown indirect branches
30094578941 : total branches
14683485627 : taken branches
15411093314 : non-taken conditional branches
10678967524 : taken conditional branches
26090060838 : all conditional branches
21694777552 : executed forward branches (+15.8%)
1679657684 : taken forward branches (-78.5%)
4863157010 : executed backward branches (-33.8%)
2286864783 : taken backward branches (-19.8%)
1866969944 : executed unconditional branches (-53.4%)
2800009758 : all function calls (-16.5%)
673537882 : indirect calls (-46.7%)
137784052 : PLT calls (=)
256484195370 : executed instructions (-1.2%)
76738590906 : executed load instructions (-0.4%)
43910090648 : executed store instructions (-0.0%)
4541628185 : taken jump table branches (=)
0 : taken unknown indirect branches (=)
28424904506 : total branches (-5.5%)
5833492411 : taken branches (-60.3%)
22591412095 : non-taken conditional branches (+46.6%)
3966522467 : taken conditional branches (-62.9%)
26557934562 : all conditional branches (+1.8%)
BOLT-INFO: SCTC: patched 60 tail calls (57 forward) tail calls (3 backward) from a total of 60 while removing 3 double jumps and removing 50 basic blocks totalling 250 bytes of code. CTCs total execution count is 36614663 and the number of times CTCs are taken is 25417844
BOLT-INFO: FOP optimized 1 redundant load(s) and 0 unused store(s)
BOLT-INFO: Frequency of redundant loads is 15661399 and frequency of unused stores is 0
BOLT-INFO: Frequency of loads changed to use a register is 15661399 and frequency of loads changed to use an immediate is 0
BOLT-INFO: FOP deleted 1 load(s) (dyn count: 15661399) and 0 store(s)
BOLT-INFO: FRAME ANALYSIS: 2248 function(s) were not optimized.
BOLT-INFO: FRAME ANALYSIS: 1999 function(s) (88.8% dyn cov) could not have its frame indices restored.
BOLT-INFO: Shrink wrapping moved 14 spills inserting load/stores and 0 spills inserting push/pops
BOLT-INFO: Shrink wrapping reduced 117436164 store executions (0.0% total instructions executed, 0.3% store instructions)
BOLT-INFO: Shrink wrapping failed at reducing 0 store executions (0.0% total instructions executed, 0.0% store instructions)
BOLT-INFO: Allocation combiner: 22 empty spaces coalesced (dyn count: 84363257).
BOLT-INFO: patched build-id (flipped last bit)
BOLT-INFO: setting _end to 0xcf093c
BOLT-INFO: setting _end to 0xcf093c
BOLT-INFO: setting __hot_start to 0xa00000
BOLT-INFO: setting __hot_end to 0xb7d512
touch profile-bolt-stamp
make[1]: Leaving directory '/home/leesm/Workspace/cpython'
leesm@leesm-ubuntu ~/Workspace/cpython ./python
Python 3.12.7 (main, Nov 2 2024, 17:57:45) [GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()
leesm@leesm-ubuntu ~/Workspace/cpython llvm-bolt --version
LLVM (http://llvm.org/):
LLVM version 19.1.0
Optimized build with assertions.
BOLT revision <unknown>
Registered Targets:
aarch64 - AArch64 (little endian)
aarch64_32 - AArch64 (little endian ILP32)
aarch64_be - AArch64 (big endian)
arm64 - ARM64 (little endian)
arm64_32 - ARM64 (little endian ILP32)
x86 - 32-bit X86: Pentium-Pro and above
x86-64 - 64-bit X86: EM64T and AMD64I tested this issue on my setup with CPython 3.12 and LLVM-BOLT version 19.1.0 on a Ubuntu(20.04) environment, and I did not encounter any problems. The --enable-bolt function worked as expected. It appears that this issue might be other environment problems. @ptr1337 |
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After Python 3.13 got pushed to archlinux stable, im still not able to bolt it with the same issues. |
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I can confirm this issue using Clang-20git (c660b281b60085cbe40d73d692badd43d7708d20) on CachyOS with Python 3.13.1: And if I do as advised by BOLT, I see another function that errors out instead:
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Also, another idea: |
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Adding to the bolt commands: |
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The I think a proper fix here is to add any functions with computed gotos to the BOLT exclusion list. Presumably a future LLVM release will gain the ability to perform these dynamic relocations, so we'll [eventually] want some form of LLVM version sniffing to control the behavior. |
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@indygreg This might be the relevant LLVM-MR for gaining that functionality: llvm/llvm-project#120267 |
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Nice find, @ms178! I agree that PR looks promising. Hopefully it makes LLVM 20. While I'm here, python-build-standalone is working around the issue with a patch at astral-sh/python-build-standalone#463. I needed to add |
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@indygreg While at it, I'd suggest to modernize the BOLT flags a bit: |
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Good idea! FWIW But |
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It's a bit off-topic here, but could you expand on this? Would it fail at build or runtime on aarch64? |
Is there something like Discord for CPython? Maybe it is more convenient we can chat there ? |
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My Discord username is |
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Ok, it seems that there is no notification in github. So I often miss important message... |
Bug report
Bug description:
Hi together,
After updating llvm-bolt to 19.1.0 it is not possible to use the --enable-bolt function anymore.
Following can be found in the log:
so, it appears to fail at the instrumentation and suggest to add
--skip-funcs=sre_ucs1_match/*.CPython versions tested on:
3.12
Operating systems tested on:
Linux
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