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Move prioritized text linker optimization code from setup.py to cmake (#160078)

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Note. This is a replica PR of #155901 which will be closed. I had to create a new PR in order to add it into my ghstack as there are some later commits which depend on it.

### Summary

🚀 This PR moves the prioritized text linker optimization from setup.py to cmake ( and enables by default on Linux aarch64 systems )

This change consolidates what was previously manual CI logic into a single location (cmake), ensuring consistent behavior across local builds, CI pipelines, and developer environments.

### Motivation
Prioritized text layout has measurable performance benefits on Arm systems by reducing code padding and improving cache utilization. This optimization was previously triggered manually via CI scripts (.ci/aarch64_linux/aarch64_ci_build.sh) or user-set environment variables. By detecting the target architecture within setup.py, this change enables the optimization automatically where applicable, improving maintainability and usability.

Note:

Due to ninja/cmake graph generation issues we cannot apply the linker file globally to all targets to the targets must be manually defined. See CMakeLists.txt the main libraries torch_python, torch, torch_cpu, torch_cuda, torch_xpu have been targetted which should be enough to maintain the performance benefits outlined above.

Co-authored-by: Usamah Zaheer <usamah.zaheer@arm.com>

Pull Request resolved: https://github.com/pytorch/pytorch/pull/160078
Approved by: https://github.com/seemethere
This commit is contained in:
Robert Hardwick
2025-09-18 08:42:03 +00:00
committed by PyTorch MergeBot
parent 56893ca1f6
commit 1aeac304b8
8 changed files with 116 additions and 29 deletions
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24
setup.py
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@ -227,9 +227,6 @@
# Static link mimalloc into C10, and use mimalloc in alloc_cpu & alloc_free.
# By default, It is only enabled on Windows.
#
# USE_PRIORITIZED_TEXT_FOR_LD
# Uses prioritized text form cmake/prioritized_text.txt for LD
#
# BUILD_LIBTORCH_WHL
# Builds libtorch.so and its dependencies as a wheel
#
@ -323,7 +320,6 @@ from tools.setup_helpers.env import (
IS_LINUX,
IS_WINDOWS,
)
from tools.setup_helpers.generate_linker_script import gen_linker_script
def str2bool(value: str | None) -> bool:
@ -1627,26 +1623,6 @@ def main() -> None:
if BUILD_PYTHON_ONLY:
install_requires += [f"{LIBTORCH_PKG_NAME}=={TORCH_VERSION}"]
if str2bool(os.getenv("USE_PRIORITIZED_TEXT_FOR_LD")):
gen_linker_script(
filein="cmake/prioritized_text.txt", fout="cmake/linker_script.ld"
)
linker_script_path = os.path.abspath("cmake/linker_script.ld")
os.environ["LDFLAGS"] = os.getenv("LDFLAGS", "") + f" -T{linker_script_path}"
os.environ["CFLAGS"] = (
os.getenv("CFLAGS", "") + " -ffunction-sections -fdata-sections"
)
os.environ["CXXFLAGS"] = (
os.getenv("CXXFLAGS", "") + " -ffunction-sections -fdata-sections"
)
elif platform.system() == "Linux" and platform.processor() == "aarch64":
print_box(
"""
WARNING: we strongly recommend enabling linker script optimization for ARM + CUDA.
To do so please export USE_PRIORITIZED_TEXT_FOR_LD=1
"""
)
# Parse the command line and check the arguments before we proceed with
# building deps and setup. We need to set values so `--help` works.
dist = Distribution()