binary-size

name	binary-size
description	Analyze and reduce ExecuTorch binary size. Use when investigating binary size, running size tests, or optimizing the runtime for size-constrained deployments.

Binary Size

Start from the main branch of executorch

Ask the user where the executorch repo is.

git checkout main && git pull

Build and measure baseline

conda activate executorch
bash test/build_size_test.sh
strip -o /tmp/size_test_stripped cmake-out/test/size_test
strip -o /tmp/size_test_all_ops_stripped cmake-out/test/size_test_all_ops
ls -la /tmp/size_test_stripped /tmp/size_test_all_ops_stripped

Produces two binaries:

• cmake-out/test/size_test — ExecuTorch runtime without operator implementations
• cmake-out/test/size_test_all_ops — ExecuTorch runtime with portable ops

Analyze with bloaty

bloaty cmake-out/test/size_test -d symbols -n 30   # by symbol
bloaty cmake-out/test/size_test -d sections        # by ELF section
bloaty <after> -- <before>                          # diff two builds
nm -S <binary> | sort -k2 -rn | head -30           # symbol sizes
strings <binary> | less                             # string literals in .rodata

Note: bloaty -d compileunits requires debug info (-g). The Release build does not include it.

Key build flags

Set by test/build_size_test.sh:

• CMAKE_BUILD_TYPE=Release
• EXECUTORCH_OPTIMIZE_SIZE=ON — enables -Os, -fno-exceptions, -fno-rtti, unwind table suppression
• CXXFLAGS="-fno-exceptions -fno-rtti -Wall -Werror"

Constraints

• Use CMake to build (not Buck)
• C++17 minimum language standard
• Must build on GCC 9 (CI uses executorch-ubuntu-22.04-gcc9-nopytorch) and Clang 12 — avoid compiler-specific flags or pragmas without version guards
• Do not regress existing functionality — run tests for modified files
• Do not change build flags in build_size_test.sh for size reductions
• Do not increase latency in the core runtime

Where to look for size reductions

• .text: look for large functions, template bloat, duplicate instantiations
• .rodata: verbose error messages, format strings, embedded file paths (__FILE__)
• .eh_frame: should already be suppressed when EXECUTORCH_OPTIMIZE_SIZE=ON
• Static init functions (nm -S <binary> | grep GLOBAL__sub_I): use constexpr constructors to constant-initialize static arrays
• Logging strings: ET_LOG_ENABLED=0 in Release eliminates format strings; ensure it propagates to consumers via PUBLIC compile definitions on cmake targets
• Inline header functions: watch for compile-define mismatches between library and consumer TUs (e.g. ET_LOG_ENABLED set in library but not in consumer)

For each change

1. Create a branch: git checkout -b binary-size-<N>
2. Implement, rebuild, measure stripped sizes
3. Create a separate PR — one logical change per PR
4. Record results in binary-size-<N>.md:

Binary	This change (N vs N-1)	Cumulative (N vs main)
size_test (stripped)	-X	-Y
size_test_all_ops (stripped)	-X	-Y

5. Update the CI size threshold in .github/workflows/pull.yml if sizes decrease