From owner-dev-commits-src-main@freebsd.org Wed Feb 3 16:04:29 2021 Return-Path: Delivered-To: dev-commits-src-main@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 570CF53B353; Wed, 3 Feb 2021 16:04:29 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "R3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4DW6245jNsz4nwN; Wed, 3 Feb 2021 16:04:28 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org (gitrepo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id A5A5D23E86; Wed, 3 Feb 2021 16:04:28 +0000 (UTC) (envelope-from git@FreeBSD.org) Received: from gitrepo.freebsd.org ([127.0.1.44]) by gitrepo.freebsd.org (8.16.1/8.16.1) with ESMTP id 113G4SYR019038; Wed, 3 Feb 2021 16:04:28 GMT (envelope-from git@gitrepo.freebsd.org) Received: (from git@localhost) by gitrepo.freebsd.org (8.16.1/8.16.1/Submit) id 113G4SQq019037; Wed, 3 Feb 2021 16:04:28 GMT (envelope-from git) Date: Wed, 3 Feb 2021 16:04:28 GMT Message-Id: <202102031604.113G4SQq019037@gitrepo.freebsd.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org From: Alex Richardson Subject: git: 8fa6abb6f4f6 - main - Expose clang's alignment builtins and use them for roundup2/rounddown2 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Git-Committer: arichardson X-Git-Repository: src X-Git-Refname: refs/heads/main X-Git-Reftype: branch X-Git-Commit: 8fa6abb6f4f64f4f23e2920e2aea7996566851a4 Auto-Submitted: auto-generated X-BeenThere: dev-commits-src-main@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Commit messages for the main branch of the src repository List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 03 Feb 2021 16:04:32 -0000 The branch main has been updated by arichardson: URL: https://cgit.FreeBSD.org/src/commit/?id=8fa6abb6f4f64f4f23e2920e2aea7996566851a4 commit 8fa6abb6f4f64f4f23e2920e2aea7996566851a4 Author: Alex Richardson AuthorDate: 2021-02-03 15:27:17 +0000 Commit: Alex Richardson CommitDate: 2021-02-03 16:02:54 +0000 Expose clang's alignment builtins and use them for roundup2/rounddown2 This makes roundup2/rounddown2 type- and const-preserving and allows using it on pointer types without casting to uintptr_t first. Not performing pointer-to-integer conversions also helps the compiler's optimization passes and can therefore result in better code generation. When using it with integer values there should be no change other than the compiler checking that the alignment value is a valid power-of-two. I originally implemented these builtins for CHERI a few years ago and they have been very useful for CheriBSD. However, they are also useful for non-CHERI code so I was able to upstream them for Clang 10.0. Rationale from the clang documentation: Clang provides builtins to support checking and adjusting alignment of pointers and integers. These builtins can be used to avoid relying on implementation-defined behavior of arithmetic on integers derived from pointers. Additionally, these builtins retain type information and, unlike bitwise arithmetic, they can perform semantic checking on the alignment value. There is also a feature request for GCC, so GCC may also support it in the future: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98641 Reviewed By: brooks, jhb, imp Differential Revision: https://reviews.freebsd.org/D28332 --- sys/sys/cdefs.h | 19 +++++++++++++++++++ sys/sys/param.h | 4 ++-- 2 files changed, 21 insertions(+), 2 deletions(-) diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h index 75bedd4b8128..72ef942084f2 100644 --- a/sys/sys/cdefs.h +++ b/sys/sys/cdefs.h @@ -884,4 +884,23 @@ #define __guarded_by(x) __lock_annotate(guarded_by(x)) #define __pt_guarded_by(x) __lock_annotate(pt_guarded_by(x)) +/* Alignment builtins for better type checking and improved code generation. */ +/* Provide fallback versions for other compilers (GCC/Clang < 10): */ +#if !__has_builtin(__builtin_is_aligned) +#define __builtin_is_aligned(x, align) \ + (((__uintptr_t)x & ((align) - 1)) == 0) +#endif +#if !__has_builtin(__builtin_align_up) +#define __builtin_align_up(x, align) \ + ((__typeof__(x))(((__uintptr_t)(x)+((align)-1))&(~((align)-1)))) +#endif +#if !__has_builtin(__builtin_align_down) +#define __builtin_align_down(x, align) \ + ((__typeof__(x))((x)&(~((align)-1)))) +#endif + +#define __align_up(x, y) __builtin_align_up(x, y) +#define __align_down(x, y) __builtin_align_down(x, y) +#define __is_aligned(x, y) __builtin_is_aligned(x, y) + #endif /* !_SYS_CDEFS_H_ */ diff --git a/sys/sys/param.h b/sys/sys/param.h index 079357a19d47..d6f1eb21dcd2 100644 --- a/sys/sys/param.h +++ b/sys/sys/param.h @@ -305,9 +305,9 @@ #endif #define nitems(x) (sizeof((x)) / sizeof((x)[0])) #define rounddown(x, y) (((x)/(y))*(y)) -#define rounddown2(x, y) ((x)&(~((y)-1))) /* if y is power of two */ +#define rounddown2(x, y) __align_down(x, y) /* if y is power of two */ #define roundup(x, y) ((((x)+((y)-1))/(y))*(y)) /* to any y */ -#define roundup2(x, y) (((x)+((y)-1))&(~((y)-1))) /* if y is powers of two */ +#define roundup2(x, y) __align_up(x, y) /* if y is powers of two */ #define powerof2(x) ((((x)-1)&(x))==0) /* Macros for min/max. */