Add embedded code-size benchmarking scripts

scripts/embedded_bench.sh

@@ -0,0 +1,127 @@
+#!/bin/bash
+
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Cross-compile the generated many_conditionals.emb.h header on embedded
+# toolchains and report .text and per-function sizes for the generated Ok()
+# methods.
+#
+# Usage:  scripts/embedded_bench.sh [out-dir]
+#         out-dir defaults to /tmp/embedded-bench.
+#
+# Run from a clean checkout. Each target compiles a tiny freestanding TU that
+# forces the relevant Ok() methods to be emitted, then reports `size` on the
+# resulting object file plus the key Ok() symbol sizes from `nm`. Only the
+# out-dir is written to: the header is refreshed in place via
+# scripts/regenerate_goldens.py, whose output is byte-identical to the
+# checked-in goldens on a clean tree.
+#
+# Targets are skipped (with a warning) when their toolchain is missing:
+#   * ARM Cortex-M4 / Thumb-2   arm-none-eabi-g++
+#   * MicroBlaze (big-endian)   /opt/microblaze/.../microblaze-buildroot-linux-gnu-g++
+#   * Host x86-64               g++ (reference)
+#
+# Compiler flags can be overridden via the EMBOSS_BENCH_FLAGS environment
+# variable; profile_tool.py uses this to sweep optimization levels.
+
+set -euo pipefail
+
+OUT="${1:-/tmp/embedded-bench}"
+REPO="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+mkdir -p "$OUT"
+
+# Refresh the golden header from the current .emb + generator so we measure the
+# live state of the code generator and not a stale checked-in header.
+python3 "$REPO/scripts/regenerate_goldens.py" >/dev/null
+
+# Tiny TU that pulls Ok() into the object file. Without a caller each Ok() is a
+# weak inline symbol the linker would dead-strip, leaving nothing to measure.
+DRIVER="$OUT/driver.cc"
+cat >"$DRIVER" <<'CPP'
+#include <cstdint>
+
+#include "testdata/many_conditionals.emb.h"
+
+// Volatile sink so the optimizer can't fold the Ok() call away.
+volatile bool emboss_result_sink;
+
+extern "C" void large_ok(const char *buf) {
+  auto v = emboss::test::MakeLargeConditionalsView(buf, 100);
+  emboss_result_sink = v.Ok();
+}
+CPP
+
+# -Os for embedded space optimization; -ffunction-sections / -fdata-sections so
+# each function lands in its own section (makes the object's `size` and
+# `nm --size-sort` directly comparable across compiles); -fno-exceptions /
+# -fno-rtti to match typical embedded builds.
+EMBEDDED_FLAGS="${EMBOSS_BENCH_FLAGS:-"-std=c++17 -Os -ffunction-sections -fdata-sections -fno-exceptions -fno-rtti"}"
+
+# -I"$REPO" resolves the header's runtime/cpp/*.h includes. The driver includes
+# "testdata/many_conditionals.emb.h", but the generated header lives under
+# testdata/golden_cpp/, so drop a symlink and add it to the include path.
+mkdir -p "$OUT/include/testdata"
+ln -sf "$REPO/testdata/golden_cpp/many_conditionals.emb.h" \
+  "$OUT/include/testdata/many_conditionals.emb.h"
+INCLUDES="-I$REPO -I$OUT/include"
+
+report_size() {
+  local label="$1"
+  local nm_bin="$2"
+  local obj="$3"
+  echo "=== $label ==="
+  # Host binutils `size` reads ELF objects for every arch we emit here, so use
+  # it unconditionally rather than a per-target `size`.
+  size "$obj"
+  echo "--- LargeConditionals::Ok() ---"
+  # The template parameter list itself contains '>' characters, so anchor on
+  # '>::Ok() const' at end of line to match the outermost Ok() and not any
+  # nested inner view's Ok().
+  "$nm_bin" --size-sort -S --demangle "$obj" 2>/dev/null |
+    grep -E "GenericLargeConditionalsView<.*>::Ok\(\) const$" | tail -1 ||
+    true
+}
+
+# --- ARM Cortex-M4 / Thumb-2 (STM32 family) ---
+if command -v arm-none-eabi-g++ >/dev/null 2>&1; then
+  ARM_OBJ="$OUT/many_conditionals.thumb.o"
+  arm-none-eabi-g++ $EMBEDDED_FLAGS \
+    -mthumb -mcpu=cortex-m4 -mfloat-abi=soft \
+    $INCLUDES -c "$DRIVER" -o "$ARM_OBJ"
+  report_size "ARM Cortex-M4 (Thumb-2, -Os)" arm-none-eabi-nm "$ARM_OBJ"
+else
+  echo "WARNING: arm-none-eabi-g++ not found, skipping ARM Cortex-M4 bench." >&2
+fi
+
+# --- MicroBlaze (big-endian) ---
+MB_PREFIX="/opt/microblaze/microblazebe--glibc--stable-2025.08-1/bin/microblaze-buildroot-linux-gnu"
+if [ -x "$MB_PREFIX-g++" ]; then
+  MB_OBJ="$OUT/many_conditionals.microblaze.o"
+  "$MB_PREFIX-g++" $EMBEDDED_FLAGS \
+    $INCLUDES -c "$DRIVER" -o "$MB_OBJ"
+  report_size "MicroBlaze (big-endian, -Os)" "$MB_PREFIX-nm" "$MB_OBJ"
+else
+  echo "WARNING: MicroBlaze g++ not found at $MB_PREFIX-g++, skipping MicroBlaze bench." >&2
+fi
+
+# --- Host x86-64 reference, same flags, for comparison ---
+if command -v g++ >/dev/null 2>&1; then
+  HOST_OBJ="$OUT/many_conditionals.x86_64.o"
+  g++ $EMBEDDED_FLAGS \
+    $INCLUDES -c "$DRIVER" -o "$HOST_OBJ"
+  report_size "Host x86-64 (-Os)" nm "$HOST_OBJ"
+else
+  echo "WARNING: g++ not found, skipping Host x86-64 bench." >&2
+fi