From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Rybchenko Subject: [PATCH v3 1/8] net/sfc/base: cope with clang warning on negative shift Date: Wed, 25 Apr 2018 18:51:37 +0100 Message-ID: <1524678704-29354-2-git-send-email-arybchenko@solarflare.com> References: <1523035280-24873-1-git-send-email-arybchenko@solarflare.com> <1524678704-29354-1-git-send-email-arybchenko@solarflare.com> Mime-Version: 1.0 Content-Type: text/plain To: Return-path: Received: from dispatch1-us1.ppe-hosted.com (dispatch1-us1.ppe-hosted.com [67.231.154.164]) by dpdk.org (Postfix) with ESMTP id 3ABB68E6E for ; Wed, 25 Apr 2018 19:51:55 +0200 (CEST) Received: from webmail.solarflare.com (webmail.solarflare.com [12.187.104.26]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1-us3.ppe-hosted.com (Proofpoint Essentials ESMTP Server) with ESMTPS id 1B88C98008C for ; Wed, 25 Apr 2018 17:51:54 +0000 (UTC) Received: from uklogin.uk.solarflarecom.com (uklogin.uk.solarflarecom.com [10.17.10.10]) by opal.uk.solarflarecom.com (8.13.8/8.13.8) with ESMTP id w3PHpoUO030294 for ; Wed, 25 Apr 2018 18:51:50 +0100 Received: from uklogin.uk.solarflarecom.com (localhost.localdomain [127.0.0.1]) by uklogin.uk.solarflarecom.com (8.13.8/8.13.8) with ESMTP id w3PHpo2n029397 for ; Wed, 25 Apr 2018 18:51:50 +0100 In-Reply-To: <1524678704-29354-1-git-send-email-arybchenko@solarflare.com> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" clang 4.0.1-6 on Ubuntu generates false positive warning that shift is negative. It is done regardless of the fact that the branch is not taken because of previous check. The warning is generate in EFX_INSERT_NATIVE32 used by EFX_INSERT_FIELD_NATIVE32. All similar cases are fixed as well. It is undesirable to suppress the warning completely. Signed-off-by: Andrew Rybchenko --- drivers/net/sfc/base/efx_types.h | 38 ++++++++++++++++++++++++-------------- 1 file changed, 24 insertions(+), 14 deletions(-) diff --git a/drivers/net/sfc/base/efx_types.h b/drivers/net/sfc/base/efx_types.h index 0581f67f4..65168ab79 100644 --- a/drivers/net/sfc/base/efx_types.h +++ b/drivers/net/sfc/base/efx_types.h @@ -328,6 +328,16 @@ extern int fix_lint; #define FIX_LINT(_x) (_x) #endif +/* + * Saturation arithmetic subtract with minimum equal to zero. + * + * Use saturating arithmetic to ensure a non-negative result. This + * avoids undefined behaviour (and compiler warnings) when used as a + * shift count. + */ +#define EFX_SSUB(_val, _sub) \ + ((_val) > (_sub) ? ((_val) - (_sub)) : 0) + /* * Extract bit field portion [low,high) from the native-endian element * which contains bits [min,max). @@ -347,8 +357,8 @@ extern int fix_lint; ((FIX_LINT(_low > _max) || FIX_LINT(_high < _min)) ? \ 0U : \ ((_low > _min) ? \ - ((_element) >> (_low - _min)) : \ - ((_element) << (_min - _low)))) + ((_element) >> EFX_SSUB(_low, _min)) : \ + ((_element) << EFX_SSUB(_min, _low)))) /* * Extract bit field portion [low,high) from the 64-bit little-endian @@ -537,29 +547,29 @@ extern int fix_lint; (((_low > _max) || (_high < _min)) ? \ 0U : \ ((_low > _min) ? \ - (((uint64_t)(_value)) << (_low - _min)) : \ - (((uint64_t)(_value)) >> (_min - _low)))) + (((uint64_t)(_value)) << EFX_SSUB(_low, _min)) :\ + (((uint64_t)(_value)) >> EFX_SSUB(_min, _low)))) #define EFX_INSERT_NATIVE32(_min, _max, _low, _high, _value) \ (((_low > _max) || (_high < _min)) ? \ 0U : \ ((_low > _min) ? \ - (((uint32_t)(_value)) << (_low - _min)) : \ - (((uint32_t)(_value)) >> (_min - _low)))) + (((uint32_t)(_value)) << EFX_SSUB(_low, _min)) :\ + (((uint32_t)(_value)) >> EFX_SSUB(_min, _low)))) #define EFX_INSERT_NATIVE16(_min, _max, _low, _high, _value) \ (((_low > _max) || (_high < _min)) ? \ 0U : \ (uint16_t)((_low > _min) ? \ - ((_value) << (_low - _min)) : \ - ((_value) >> (_min - _low)))) + ((_value) << EFX_SSUB(_low, _min)) : \ + ((_value) >> EFX_SSUB(_min, _low)))) #define EFX_INSERT_NATIVE8(_min, _max, _low, _high, _value) \ (((_low > _max) || (_high < _min)) ? \ 0U : \ (uint8_t)((_low > _min) ? \ - ((_value) << (_low - _min)) : \ - ((_value) >> (_min - _low)))) + ((_value) << EFX_SSUB(_low, _min)) : \ + ((_value) >> EFX_SSUB(_min, _low)))) /* * Construct bit field portion @@ -1288,22 +1298,22 @@ extern int fix_lint; #define EFX_SHIFT64(_bit, _base) \ (((_bit) >= (_base) && (_bit) < (_base) + 64) ? \ - ((uint64_t)1 << ((_bit) - (_base))) : \ + ((uint64_t)1 << EFX_SSUB((_bit), (_base))) : \ 0U) #define EFX_SHIFT32(_bit, _base) \ (((_bit) >= (_base) && (_bit) < (_base) + 32) ? \ - ((uint32_t)1 << ((_bit) - (_base))) : \ + ((uint32_t)1 << EFX_SSUB((_bit),(_base))) : \ 0U) #define EFX_SHIFT16(_bit, _base) \ (((_bit) >= (_base) && (_bit) < (_base) + 16) ? \ - (uint16_t)(1 << ((_bit) - (_base))) : \ + (uint16_t)(1 << EFX_SSUB((_bit), (_base))) : \ 0U) #define EFX_SHIFT8(_bit, _base) \ (((_bit) >= (_base) && (_bit) < (_base) + 8) ? \ - (uint8_t)(1 << ((_bit) - (_base))) : \ + (uint8_t)(1 << EFX_SSUB((_bit), (_base))) : \ 0U) #define EFX_SET_OWORD_BIT64(_oword, _bit) \ -- 2.14.1