diff --git a/libcxx/test/benchmarks/spec.gen.py b/libcxx/test/benchmarks/spec.gen.py
new file mode 100644
index 0000000000000..0994c9d54abfa
--- /dev/null
+++ b/libcxx/test/benchmarks/spec.gen.py
@@ -0,0 +1,73 @@
+# ===----------------------------------------------------------------------===##
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+# ===----------------------------------------------------------------------===##
+
+# REQUIRES: enable-spec-benchmarks
+
+# RUN: mkdir -p %T
+# RUN: echo "%{cxx}" > %T/cxx.subs
+# RUN: echo "%{compile_flags}" > %T/compile_flags.subs
+# RUN: echo "%{flags}" > %T/flags.subs
+# RUN: echo "%{link_flags}" > %T/link_flags.subs
+# RUN: echo "%{spec_dir}" > %T/spec_dir.subs
+# RUN: %{python} %s %T
+# END.
+
+import json
+import pathlib
+import sys
+
+test_dir = pathlib.Path(sys.argv[1])
+cxx = (test_dir / 'cxx.subs').open().read().strip()
+compile_flags = (test_dir / 'compile_flags.subs').open().read().strip()
+flags = (test_dir / 'flags.subs').open().read().strip()
+link_flags = (test_dir / 'link_flags.subs').open().read().strip()
+spec_dir = pathlib.Path((test_dir / 'spec_dir.subs').open().read().strip())
+
+# Setup the configuration file
+test_dir.mkdir(parents=True, exist_ok=True)
+spec_config = test_dir / 'spec-config.cfg'
+spec_config.write_text(f"""
+default:
+    ignore_errors        = 1
+    iterations           = 1
+    label                = spec-stdlib
+    log_line_width       = 4096
+    makeflags            = --jobs=8
+    mean_anyway          = 1
+    output_format        = csv
+    preenv               = 0
+    reportable           = 0
+    tune                 = base
+    copies               = 1
+    threads              = 1
+    CC                   = cc -O3
+    CXX                  = {cxx} {compile_flags} {flags} {link_flags} -Wno-error
+    CC_VERSION_OPTION    = --version
+    CXX_VERSION_OPTION   = --version
+    EXTRA_PORTABILITY    = -DSPEC_NO_CXX17_SPECIAL_MATH_FUNCTIONS # because libc++ doesn't implement the special math functions yet
+""")
+
+# Build the list of benchmarks. We take all intrate and fprate benchmarks that contain C++ and
+# discard the ones that contain Fortran, since this test suite isn't set up to build Fortran code.
+spec_benchmarks = set()
+no_fortran = set()
+with open(spec_dir / 'benchspec' / 'CPU' / 'intrate_any_cpp.bset', 'r') as f:
+    spec_benchmarks.update(json.load(f)['benchmarks'])
+with open(spec_dir / 'benchspec' / 'CPU' / 'fprate_any_cpp.bset', 'r') as f:
+    spec_benchmarks.update(json.load(f)['benchmarks'])
+with open(spec_dir / 'benchspec' / 'CPU' / 'no_fortran.bset', 'r') as f:
+    no_fortran.update(json.load(f)['benchmarks'])
+spec_benchmarks &= no_fortran
+
+for benchmark in spec_benchmarks:
+    print(f'#--- {benchmark}.sh.test')
+    print(f'RUN: cp {spec_config} %T/spec-config.cfg')
+    print(f'RUN: rm -rf %T/output') # clean up any previous (potentially incomplete) run
+    print(f'RUN: %{{spec_dir}}/bin/runcpu --config %T/spec-config.cfg --size train --output-root %T/output --rebuild {benchmark}')
+    print(f'RUN: cp %T/output/result/*.log %T/output/result/*.train.csv %T') # copy relevant output files
+    print(f'RUN: rm -rf %T/output') # remove the temporary directory, which can become quite large
diff --git a/libcxx/utils/libcxx/test/params.py b/libcxx/utils/libcxx/test/params.py
index 81c613421a465..6f013a75195a8 100644
--- a/libcxx/utils/libcxx/test/params.py
+++ b/libcxx/utils/libcxx/test/params.py
@@ -374,6 +374,17 @@ def getSuitableClangTidy(cfg):
         help="Whether to run the benchmarks in the test suite, to only dry-run them or to disable them entirely.",
         actions=lambda mode: [AddFeature(f"enable-benchmarks={mode}")],
     ),
+    Parameter(
+        name="spec_dir",
+        type=str,
+        default="none",
+        help="Path to the SPEC benchmarks. This is required in order to run the SPEC benchmarks as part of "
+             "the libc++ test suite. If provided, the appropriate SPEC toolset must already be built and installed.",
+        actions=lambda spec_dir: [
+            AddSubstitution("%{spec_dir}", spec_dir),
+            AddFeature('enable-spec-benchmarks')
+        ] if spec_dir != "none" else [],
+    ),
     Parameter(
         name="long_tests",
         choices=[True, False],

--- test/benchmarks/spec.gen.py	2025-09-04 20:18:48.000000 +0000
+++ test/benchmarks/spec.gen.py	2025-09-04 20:22:05.286978 +0000
@@ -20,20 +20,21 @@
 import json
 import pathlib
 import sys
 
 test_dir = pathlib.Path(sys.argv[1])
-cxx = (test_dir / 'cxx.subs').open().read().strip()
-compile_flags = (test_dir / 'compile_flags.subs').open().read().strip()
-flags = (test_dir / 'flags.subs').open().read().strip()
-link_flags = (test_dir / 'link_flags.subs').open().read().strip()
-spec_dir = pathlib.Path((test_dir / 'spec_dir.subs').open().read().strip())
+cxx = (test_dir / "cxx.subs").open().read().strip()
+compile_flags = (test_dir / "compile_flags.subs").open().read().strip()
+flags = (test_dir / "flags.subs").open().read().strip()
+link_flags = (test_dir / "link_flags.subs").open().read().strip()
+spec_dir = pathlib.Path((test_dir / "spec_dir.subs").open().read().strip())
 
 # Setup the configuration file
 test_dir.mkdir(parents=True, exist_ok=True)
-spec_config = test_dir / 'spec-config.cfg'
-spec_config.write_text(f"""
+spec_config = test_dir / "spec-config.cfg"
+spec_config.write_text(
+    f"""
 default:
     ignore_errors        = 1
     iterations           = 1
     label                = spec-stdlib
     log_line_width       = 4096
@@ -48,31 +49,38 @@
     CC                   = cc -O3
     CXX                  = {cxx} {compile_flags} {flags} {link_flags} -Wno-error
     CC_VERSION_OPTION    = --version
     CXX_VERSION_OPTION   = --version
     EXTRA_PORTABILITY    = -DSPEC_NO_CXX17_SPECIAL_MATH_FUNCTIONS # because libc++ doesn't implement the special math functions yet
-""")
+"""
+)
 
 # Build the list of benchmarks. We take all intrate and fprate benchmarks that contain C++ and
 # discard the ones that contain Fortran, since this test suite isn't set up to build Fortran code.
 spec_benchmarks = set()
 no_fortran = set()
-with open(spec_dir / 'benchspec' / 'CPU' / 'intrate_any_cpp.bset', 'r') as f:
-    spec_benchmarks.update(json.load(f)['benchmarks'])
-with open(spec_dir / 'benchspec' / 'CPU' / 'fprate_any_cpp.bset', 'r') as f:
-    spec_benchmarks.update(json.load(f)['benchmarks'])
-with open(spec_dir / 'benchspec' / 'CPU' / 'no_fortran.bset', 'r') as f:
-    no_fortran.update(json.load(f)['benchmarks'])
+with open(spec_dir / "benchspec" / "CPU" / "intrate_any_cpp.bset", "r") as f:
+    spec_benchmarks.update(json.load(f)["benchmarks"])
+with open(spec_dir / "benchspec" / "CPU" / "fprate_any_cpp.bset", "r") as f:
+    spec_benchmarks.update(json.load(f)["benchmarks"])
+with open(spec_dir / "benchspec" / "CPU" / "no_fortran.bset", "r") as f:
+    no_fortran.update(json.load(f)["benchmarks"])
 spec_benchmarks &= no_fortran
 
 for benchmark in spec_benchmarks:
-    print(f'#--- {benchmark}.sh.test')
-    print(f'RUN: rm -rf %T') # clean up any previous (potentially incomplete) run
-    print(f'RUN: mkdir %T')
-    print(f'RUN: cp {spec_config} %T/spec-config.cfg')
-    print(f'RUN: %{{spec_dir}}/bin/runcpu --config %T/spec-config.cfg --size train --output-root %T --rebuild {benchmark}')
-    print(f'RUN: rm -rf %T/benchspec') # remove the temporary directory, which can become quite large
+    print(f"#--- {benchmark}.sh.test")
+    print(f"RUN: rm -rf %T")  # clean up any previous (potentially incomplete) run
+    print(f"RUN: mkdir %T")
+    print(f"RUN: cp {spec_config} %T/spec-config.cfg")
+    print(
+        f"RUN: %{{spec_dir}}/bin/runcpu --config %T/spec-config.cfg --size train --output-root %T --rebuild {benchmark}"
+    )
+    print(
+        f"RUN: rm -rf %T/benchspec"
+    )  # remove the temporary directory, which can become quite large
 
     # Parse the results into a LNT-compatible format. This also errors out if there are no CSV files, which
     # means that the benchmark didn't run properly (the `runcpu` command above never reports a failure).
-    print(f'RUN: %{{libcxx-dir}}/utils/parse-spec-result %T/result/CPUv8.001.*.train.csv --output-format=lnt > %T/results.lnt')
-    print(f'RUN: cat %T/results.lnt')
+    print(
+        f"RUN: %{{libcxx-dir}}/utils/parse-spec-result %T/result/CPUv8.001.*.train.csv --output-format=lnt > %T/results.lnt"
+    )
+    print(f"RUN: cat %T/results.lnt")