Date: Mon, 2 Mar 2020 12:29:55 -0800 From: Mark Millard <marklmi@yahoo.com> To: Konstantin Belousov <kib@freebsd.org>, svn-src-head@freebsd.org Subject: Re: svn commit: r358439 - head/sys/amd64/include Message-ID: <4ED174D6-EBC4-4F0D-B9C5-639E10016C4D@yahoo.com> References: <4ED174D6-EBC4-4F0D-B9C5-639E10016C4D.ref@yahoo.com>
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Konstantin Belousov kostikbel at gmail.com wrote on Mon Mar 2 18:27:05 UTC 2020 ": > On Mon, Mar 02, 2020 at 09:13:53AM -0800, Ryan Libby wrote: > > On Mon, Mar 2, 2020 at 12:45 AM Alexander V. Chernikov <melifaro at ipfw.ru> wrote: > > > > > > 28.02.2020, 18:32, "Ryan Libby" <rlibby at freebsd.org>: > > > > Author: rlibby > > > > Date: Fri Feb 28 18:32:36 2020 > > > > New Revision: 358439 > > > > URL: https://svnweb.freebsd.org/changeset/base/358439 > > > > > > > > Log: > > > > amd64 atomic.h: minor codegen optimization in flag access > > > > > > > > Previously the pattern to extract status flags from inline assembly > > > > blocks was to use setcc in the block to write the flag to a register. > > > > This was suboptimal in a few ways: > > > > - It would lead to code like: sete %cl; test %cl; jne, i.e. a flag > > > > would just be loaded into a register and then reloaded to a flag. > > > > - The setcc would force the block to use an additional register. > > > > - If the client code didn't care for the flag value then the setcc > > > > would be entirely pointless but could not be eliminated by the > > > > optimizer. > > > > > > > > A more modern inline asm construct (since gcc 6 and clang 9) allows for > > > This effectively restricts kernel builds by all older compilers. > > > Is there any chance of making it conditional depending on the compiler version/features? > What is the older compiler you need to use for base system ? > And why ? [A copy of something I sent to svn-src-head and rlibby a on Feb 29 that showed the example of 2 ports failing to build on FreeBSD build servers, where the server sent out the notice of the failure.] head -r358439 breaks unmodified ports that use, for example, clang70 and clang++70: https://lists.freebsd.org/pipermail/freebsd-emulation/2020-February/017672.html https://lists.freebsd.org/pipermail/freebsd-emulation/2020-February/017675.html show things like . . . kBuild: Compiling HGSMIGuestR0Lib - /wrkdirs/usr/ports/emulators/virtualbox-ose-nox11/work/VirtualBox-5.2.34/src/VBox/GuestHost/HGSMI/HGSMICommon.cpp clang-7: warning: argument unused during compilation: '--param inline-unit-growth=100' [-Wunused-command-line-argument] clang-7: warning: argument unused during compilation: '--param large-function-growth=1000' [-Wunused-command-line-argument] In file included from /wrkdirs/usr/ports/emulators/virtualbox-ose-nox11/work/VirtualBox-5.2.34/src/VBox/GuestHost/HGSMI/HGSMICommon.cpp:38: In file included from /wrkdirs/usr/ports/emulators/virtualbox-ose-nox11/work/VirtualBox-5.2.34/include/VBox/Graphics/VBoxVideoIPRT.h:32: In file included from /wrkdirs/usr/ports/emulators/virtualbox-ose-nox11/work/VirtualBox-5.2.34/include/iprt/string.h:45: In file included from /usr/src/sys/sys/libkern.h:41: In file included from /usr/src/sys/sys/systm.h:44: /usr/include/machine/atomic.h:230:1: error: invalid output constraint '=@cce' in asm ATOMIC_CMPSET(char); ^ /usr/include/machine/atomic.h:205:4: note: expanded from macro 'ATOMIC_CMPSET' : "=@cce" (res), /* 0 */ \ ^ /usr/include/machine/atomic.h:230:1: error: invalid output constraint '=@cce' in asm /usr/include/machine/atomic.h:222:4: note: expanded from macro 'ATOMIC_CMPSET' : "=@cce" (res), /* 0 */ \ ^ /usr/include/machine/atomic.h:231:1: error: invalid output constraint '=@cce' in asm ATOMIC_CMPSET(short); ^ /usr/include/machine/atomic.h:205:4: note: expanded from macro 'ATOMIC_CMPSET' : "=@cce" (res), /* 0 */ \ ^ /usr/include/machine/atomic.h:231:1: error: invalid output constraint '=@cce' in asm /usr/include/machine/atomic.h:222:4: note: expanded from macro 'ATOMIC_CMPSET' : "=@cce" (res), /* 0 */ \ ^ /usr/include/machine/atomic.h:232:1: error: invalid output constraint '=@cce' in asm ATOMIC_CMPSET(int); ^ /usr/include/machine/atomic.h:205:4: note: expanded from macro 'ATOMIC_CMPSET' : "=@cce" (res), /* 0 */ \ ^ /usr/include/machine/atomic.h:232:1: error: invalid output constraint '=@cce' in asm /usr/include/machine/atomic.h:222:4: note: expanded from macro 'ATOMIC_CMPSET' : "=@cce" (res), /* 0 */ \ ^ /usr/include/machine/atomic.h:233:1: error: invalid output constraint '=@cce' in asm ATOMIC_CMPSET(long); ^ /usr/include/machine/atomic.h:205:4: note: expanded from macro 'ATOMIC_CMPSET' : "=@cce" (res), /* 0 */ \ ^ /usr/include/machine/atomic.h:233:1: error: invalid output constraint '=@cce' in asm /usr/include/machine/atomic.h:222:4: note: expanded from macro 'ATOMIC_CMPSET' : "=@cce" (res), /* 0 */ \ ^ /usr/include/machine/atomic.h:280:4: error: invalid output constraint '=@ccc' in asm : "=@ccc" (res), /* 0 */ ^ /usr/include/machine/atomic.h:296:4: error: invalid output constraint '=@ccc' in asm : "=@ccc" (res), /* 0 */ ^ /usr/include/machine/atomic.h:312:4: error: invalid output constraint '=@ccc' in asm : "=@ccc" (res), /* 0 */ ^ /usr/include/machine/atomic.h:328:4: error: invalid output constraint '=@ccc' in asm : "=@ccc" (res), /* 0 */ ^ === Mark Millard marklmi at yahoo.com ( dsl-only.net went away in early 2018-Mar)
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