From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Lobakin Subject: [PATCH v3 7/7] lib: test_bitmap: add compile-time optimization/evaluations assertions Date: Fri, 17 Jun 2022 16:40:31 +0200 Message-ID: <20220617144031.2549432-8-alexandr.lobakin@intel.com> References: <20220617144031.2549432-1-alexandr.lobakin@intel.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1655476855; x=1687012855; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=THeq/t7OeFGS7kF1qxlxBPZVHuRcSkjtN1FGjFL0hbM=; b=WiB2oJ65/7rC7dKmiifE/o5i4GQSJvwbBbKJWyw63DekzX0cSPtYA1um BtS5NwkP0JEnPh+MqOH4qyq3/K6RPkWQYwodgPATdRdTl/0QrEeEMnDNv 6c0wKm8f1rixz6eqLujFLBoXEPmMyh/+gQqbP44aNbBgbT50nXVQzgAmT P3gj514DMqVc6wDvQyTkkjiQfLpi8vLY+yvoRndyzxIthb3IphXlqeNqq AbqlfsQdbspNcn41oPrV+AK8WlvlSxnC0ZwMmIo4guHXfxHEKh6qBwVtN SzzqJWLx1Iile7Lttt85XIWlI+/ydRNBp0ATJ45Z26kB4F/fCQ/5BikUK g==; In-Reply-To: <20220617144031.2549432-1-alexandr.lobakin@intel.com> List-ID: Content-Type: text/plain; charset="us-ascii" To: Arnd Bergmann , Yury Norov Cc: Alexander Lobakin , Andy Shevchenko , Mark Rutland , Matt Turner , Brian Cain , Geert Uytterhoeven , Yoshinori Sato , Rich Felker , "David S. Miller" , Kees Cook , "Peter Zijlstra (Intel)" , Marco Elver , Borislav Petkov , Tony Luck , Maciej Fijalkowski , Jesse Brandeburg , Greg Kroah-Hartman , linux-alpha@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64 Add a function to the bitmap test suite, which will ensure that compilers are able to evaluate operations performed by the bitops/bitmap helpers to compile-time constants when all of the arguments are compile-time constants as well, or trigger a build bug otherwise. This should work on all architectures and all the optimization levels supported by Kbuild. The function doesn't perform any runtime tests and gets optimized out to nothing after passing the build assertions. Suggested-by: Yury Norov Signed-off-by: Alexander Lobakin --- lib/test_bitmap.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c index d5923a640457..3a7b09b82794 100644 --- a/lib/test_bitmap.c +++ b/lib/test_bitmap.c @@ -869,6 +869,50 @@ static void __init test_bitmap_print_buf(void) } } +static void __init test_bitmap_const_eval(void) +{ + DECLARE_BITMAP(bitmap, BITS_PER_LONG); + unsigned long initvar = BIT(2); + unsigned long bitopvar = 0; + unsigned long var = 0; + int res; + + /* + * Compilers must be able to optimize all of those to compile-time + * constants on any supported optimization level (-O2, -Os) and any + * architecture. Otherwise, trigger a build bug. + * The whole function gets optimized out then, there's nothing to do + * in runtime. + */ + + /* Equals to `unsigned long bitmap[1] = { BIT(5), }` */ + bitmap_clear(bitmap, 0, BITS_PER_LONG); + if (!test_bit(7, bitmap)) + bitmap_set(bitmap, 5, 1); + + /* Equals to `unsigned long bitopvar = BIT(20)` */ + __change_bit(31, &bitopvar); + bitmap_shift_right(&bitopvar, &bitopvar, 11, BITS_PER_LONG); + + /* Equals to `unsigned long var = BIT(25)` */ + var |= BIT(25); + if (var & BIT(0)) + var ^= GENMASK(9, 6); + + /* __const_hweight<32|64>(BIT(5)) == 1 */ + res = bitmap_weight(bitmap, 20); + BUILD_BUG_ON(!__builtin_constant_p(res)); + + /* !(BIT(31) & BIT(18)) == 1 */ + res = !test_bit(18, &bitopvar); + BUILD_BUG_ON(!__builtin_constant_p(res)); + + /* BIT(2) & GENMASK(14, 8) == 0 */ + BUILD_BUG_ON(!__builtin_constant_p(initvar & GENMASK(14, 8))); + /* ~BIT(25) */ + BUILD_BUG_ON(!__builtin_constant_p(~var)); +} + static void __init selftest(void) { test_zero_clear(); @@ -884,6 +928,7 @@ static void __init selftest(void) test_for_each_set_clump8(); test_bitmap_cut(); test_bitmap_print_buf(); + test_bitmap_const_eval(); } KSTM_MODULE_LOADERS(test_bitmap); -- 2.36.1