[clang] [clang][lit] Add option to skip clang-repl checks (PR #199255)

[Andy Kaylor via cfe-commits]

https://github.com/andykaylor created https://github.com/llvm/llvm-project/pull/199255

Whenever lit or llvm-lit is invoked to run clang tests, clang-repl is run at least once to check for host jit capabilities, and possibly several more times to probe related capabilities. This adds a noticeable delay before testing starts, especially for debug builds.

This change adds a lit parameter (clang_skip_clang_repl_checks) and an environment variable check (CLANG_LIT_SKIP_CLANG_REPL_CHECKS) to allow the clang-repl probes to be skipped. When this option is used, any tests that rely on jit execution will be reported as unsupported.

This option is intended only to allow quicker targeted testing during development. It should not be used for comprehensive verification before submitting a patch.

On my local test system, executing `ninja check-clang-cir-codegen` with a previously completed debug build took 18 seconds to run 354 tests with this option and 53 seconds without it. This is the sort of use case I am targeting -- lit test runs when the clang-repl overhead will constitute a significant portion of the total time to execute the tests.

>From 402a17937a6204a300ed80886ac09890bd90b16c Mon Sep 17 00:00:00 2001
From: Andy Kaylor <akaylor at nvidia.com>
Date: Fri, 22 May 2026 11:18:15 -0700
Subject: [PATCH] [clang][lit] Add option to skip clang-repl checks

Whenever lit or llvm-lit is invoked to run clang tests, clang-repl is
run at least once to check for host jit capabilities, and possibly
several more times to probe related capabilities. This adds a noticeable
delay before testing starts, especially for debug builds.

This change adds a lit parameter (clang_skip_clang_repl_checks) and an
environment variable check (CLANG_LIT_SKIP_CLANG_REPL_CHECKS) to allow
the clang-repl probes to be skipped. When this option is used, any tests
that rely on jit execution will be reported as unsupported.

This option is intended only to allow quicker targeted testing during
development. It should not be used for comprehensive verification before
submitting a patch.

On my local test system, executing `ninja check-clang-cir-codegen` with
a previously completed debug build took 18 seconds to run 354 tests with
this option and 53 seconds without it. This is the sort of use case I am
targeting -- lit test runs when the clang-repl overhead will constitute
a significant portion of the total time to execute the tests.
---
 clang/test/lit.cfg.py | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/clang/test/lit.cfg.py b/clang/test/lit.cfg.py
index 4a00769469543..a377bc112ddb8 100644
--- a/clang/test/lit.cfg.py
+++ b/clang/test/lit.cfg.py
@@ -231,7 +231,14 @@ def have_host_clang_repl_cuda():
 
     return False
 
-if have_host_jit_feature_support('jit'):
+skip_clang_repl_checks = lit.util.pythonize_bool(
+    lit_config.params.get(
+        "clang_skip_clang_repl_checks",
+        os.environ.get("CLANG_LIT_SKIP_CLANG_REPL_CHECKS", "0"),
+    )
+)
+
+if not skip_clang_repl_checks and have_host_jit_feature_support('jit'):
     config.available_features.add('host-supports-jit')
 
     if have_host_clang_repl_cuda():