Added simple benchmark.

tests/benchmark/interposed.c

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+/*
+ * Copyright 2025 Yury Gribov
+ *
+ * The MIT License (MIT)
+ * 
+ * Use of this source code is governed by MIT license that can be
+ * found in the LICENSE.txt file.
+ */
+
+#include "interposed.h"
+
+__attribute__((visibility("default")))
+void foo() {}

tests/benchmark/interposed.h

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+/*
+ * Copyright 2025 Yury Gribov
+ *
+ * The MIT License (MIT)
+ * 
+ * Use of this source code is governed by MIT license that can be
+ * found in the LICENSE.txt file.
+ */
+
+#ifndef INTERPOSED_H
+#define INTERPOSED_H
+
+extern void foo();
+
+#endif

tests/benchmark/main.c

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+/*
+ * Copyright 2025 Yury Gribov
+ *
+ * The MIT License (MIT)
+ * 
+ * Use of this source code is governed by MIT license that can be
+ * found in the LICENSE.txt file.
+ */
+
+#include "interposed.h"
+
+#define NITER 1000000000L
+
+int main() {
+  for (long i = 0; i < NITER; ++i)
+#ifdef BASELINE
+    asm volatile("");
+#else
+    foo();
+#endif
+
+  return 0;
+}

tests/benchmark/run.sh

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+#!/bin/sh
+
+# Copyright 2025 Yury Gribov
+#
+# The MIT License (MIT)
+# 
+# Use of this source code is governed by MIT license that can be
+# found in the LICENSE.txt file.
+
+# This is a simple benchmark of Implib's overhead.
+#
+# On my machine results are very close, Implib being 0.5-1% slower.
+
+set -eu
+
+cd $(dirname $0)
+
+if test -n "${1:-}"; then
+  ARCH="$1"
+fi
+
+. ../common.sh
+
+CFLAGS="-g -O2 $CFLAGS"
+N=10
+
+# Need sudo for nice...
+RUN='nice -n -20 taskset 1'
+
+$CC $CFLAGS -shared -fPIC interposed.c -o libinterposed.so
+${PYTHON:-} ../../implib-gen.py -q --target $TARGET libinterposed.so
+
+export LD_LIBRARY_PATH=.:${LD_LIBRARY_PATH:-}
+
+# Baseline
+
+$CC $CFLAGS -DBASELINE main.c
+
+echo "Baseline:"
+$RUN time ./a.out
+
+# Normal
+
+$CC $CFLAGS main.c -L. -linterposed $LIBS
+
+echo "Normal:"
+$RUN time ./a.out
+
+# Implib
+
+$CC $CFLAGS main.c libinterposed.so.tramp.S libinterposed.so.init.c $LIBS
+
+echo "Implib:"
+$RUN time ./a.out
+
+# Implib (IMPLIB_EXPORT_SHIMS)
+
+$CC $CFLAGS -DIMPLIB_EXPORT_SHIMS -rdynamic main.c libinterposed.so.tramp.S libinterposed.so.init.c $LIBS
+
+echo "Implib (IMPLIB_EXPORT_SHIMS):"
+$RUN time ./a.out