Date: Tue, 31 May 2011 15:26:54 +0000 From: Alexander Best <arundel@freebsd.org> To: Garrett Cooper <yanegomi@gmail.com> Cc: "freebsd-hackers@FreeBSD.ORG" <freebsd-hackers@FreeBSD.ORG>, "freebsd-toolchain@FreeBSD.ORG" <freebsd-toolchain@FreeBSD.ORG>, Dimitry Andric <dim@FreeBSD.org>, Pan Tsu <inyaoo@gmail.com> Subject: Re: [rfc] a few kern.mk and bsd.sys.mk related changes Message-ID: <20110531152654.GA42990@freebsd.org> In-Reply-To: <20110531143914.GA30260@freebsd.org> References: <20110527181459.GA29908@freebsd.org> <20110527182906.GA31871@freebsd.org> <86oc2mlsey.fsf@gmail.com> <20110528182326.GA75447@freebsd.org> <20110528202619.GA27204@muon.cran.org.uk> <20110531095742.GA99888@freebsd.org> <4DE4C4CC.4020905@FreeBSD.org> <20110531104639.GA4218@freebsd.org> <24ADBA34-A5FC-4A67-8D6F-3BDAE158285C@gmail.com> <20110531143914.GA30260@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
--zhXaljGHf11kAtnf
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
On Tue May 31 11, Alexander Best wrote:
> On Tue May 31 11, Garrett Cooper wrote:
> > On May 31, 2011, at 3:46 AM, Alexander Best <arundel@freebsd.org> wrote:
> >
> > > On Tue May 31 11, Dimitry Andric wrote:
> > >> On 2011-05-31 11:57, Alexander Best wrote:
> > >> ...
> > >>>>> however i've often read messages - mostly by bruce evans - claiming that
> > >>>>> anything greater than -O will in fact decrease a kernel's ability to be
> > >>>>> debugged just as well as a kernel with -O.
> > >>>> The critical option when -O2 is used is -fno-omit-frame-pointers, since
> > >>>> removing
> > >>>> frame pointers makes debugging impossible (on i386). With -O2 code is
> > >>>> moved around and
> > >>>> removed, so debugging is more difficult, but can still provide useful
> > >>>> information.
> > >>> any reason we cannot use -O2 -fno-omit-frame-pointers -fno-strict-aliasing
> > >>> as
> > >>> standard COPTFLAGS with debugging enabled for *all* archs?
> > >>
> > >> Most likely, the performance gain from -O2 is rather small, except for
> > >> special cases, but the pain during debugging is increased a great deal.
> > >>
> > >> Even if you add frame pointers, with -O2 large pieces of code can be
> > >> transformed, variables or even entire functions can be completely
> > >> eliminated, and so on, making debugging much more difficult.
> > >
> > > *lol* we're moving in circles. so back to the beginning: why not use -O
> > > for all archs, if debugging was enabled? for amd64 -O2 is always set, no
> > > matter, if debugging is enabled or disabled.
> >
> > I don't know, but I've run into cases where gcc has inlined or shuffled around code on amd64 with -O2 -fno-strict-aliasing, so I changed my make.conf to use -O0 when DEBUG_FLAGS was defined.
>
> ...which leads me to the conclusion that -O should be set when DEBUG was
> defined: an all ARCHS.
>
> right now -fno-omit-frame-pointer is only set on amd64 and powerpc, if the
> kernel contains DDB, KDTRACE_FRAME or HWPMC. how about this behavior? shouldn't
> -fno-omit-frame-pointer be set uncondtitionally on all archs? just like
> -fno-strict-aliasing?
so how about the following patch?
cheers.
alex
>
> cheers.
> alex
>
> > Thanks,
> > -Garrett
> --
> a13x
--
a13x
--zhXaljGHf11kAtnf
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment; filename="kern.pre.mk.diff"
diff --git a/sys/conf/Makefile.amd64 b/sys/conf/Makefile.amd64
index 5096829..f70f3de 100644
--- a/sys/conf/Makefile.amd64
+++ b/sys/conf/Makefile.amd64
@@ -31,13 +31,6 @@ S= ../../..
.endif
.include "$S/conf/kern.pre.mk"
-DDB_ENABLED!= grep DDB opt_ddb.h || true
-DTR_ENABLED!= grep KDTRACE_FRAME opt_kdtrace.h || true
-HWPMC_ENABLED!= grep HWPMC opt_hwpmc_hooks.h || true
-.if !empty(DDB_ENABLED) || !empty(DTR_ENABLED) || !empty(HWPMC_ENABLED)
-CFLAGS+= -fno-omit-frame-pointer
-.endif
-
MKMODULESENV+= MACHINE=amd64
.if ${CC:T:Mclang} == "clang"
diff --git a/sys/conf/Makefile.powerpc b/sys/conf/Makefile.powerpc
index e4cd85f..04bc66b 100644
--- a/sys/conf/Makefile.powerpc
+++ b/sys/conf/Makefile.powerpc
@@ -37,11 +37,6 @@ INCLUDES+= -I$S/contrib/libfdt
CFLAGS+= -msoft-float
-DDB_ENABLED!= grep DDB opt_ddb.h || true
-.if !empty(DDB_ENABLED)
-CFLAGS+= -fno-omit-frame-pointer
-.endif
-
%BEFORE_DEPEND
%OBJS
diff --git a/sys/conf/kern.pre.mk b/sys/conf/kern.pre.mk
index e9aa6e2..0314ada 100644
--- a/sys/conf/kern.pre.mk
+++ b/sys/conf/kern.pre.mk
@@ -24,26 +24,28 @@ OBJCOPY?= objcopy
SIZE?= size
.if defined(DEBUG)
-_MINUS_O= -O
+COPTFLAGS?= -O -pipe
CTFFLAGS+= -g
+.elif ${MACHINE_CPUARCH} == "amd64" && ${CC:T:Mclang} != "clang"
+COPTFLAGS?= -O2 -frename-registers -pipe
.else
-_MINUS_O= -O2
+COPTFLAGS?= -O2 -pipe
.endif
-.if ${MACHINE_CPUARCH} == "amd64"
-COPTFLAGS?=-O2 -frename-registers -pipe
-.else
-COPTFLAGS?=${_MINUS_O} -pipe
+
+.if !empty(COPTFLAGS:M-O[234sz]) && empty(COPTFLAGS:M-fno-strict-aliasing)
+COPTFLAGS+= -fno-strict-aliasing
.endif
-.if !empty(COPTFLAGS:M-O[23s]) && empty(COPTFLAGS:M-fno-strict-aliasing)
-COPTFLAGS+= -fno-strict-aliasing
+
+.if empty(COPTFLAGS:M-O0) && empty(COPTFLAGS:M-fno-omit-frame-pointer)
+COPTFLAGS+= -fno-omit-frame-pointer
.endif
+
.if !defined(NO_CPU_COPTFLAGS)
-COPTFLAGS+= ${_CPUCFLAGS}
+COPTFLAGS+= ${_CPUCFLAGS}
.endif
-C_DIALECT= -std=c99
-NOSTDINC= -nostdinc
-INCLUDES= ${NOSTDINC} ${INCLMAGIC} -I. -I$S
+C_DIALECT= -std=c99
+INCLUDES= -nostdinc ${INCLMAGIC} -I. -I$S
# This hack lets us use the OpenBSD altq code without spamming a new
# include path into contrib'ed source files.
@@ -146,8 +148,7 @@ SYSTEM_LD_TAIL= @${OBJCOPY} --strip-symbol gcc2_compiled. ${.TARGET} ; \
${SIZE} ${.TARGET} ; chmod 755 ${.TARGET}
SYSTEM_DEP+= ${LDSCRIPT}
-# MKMODULESENV is set here so that port makefiles can augment
-# them.
+# MKMODULESENV is set here so that port makefiles can augment them.
MKMODULESENV+= MAKEOBJDIRPREFIX=${.OBJDIR}/modules KMODDIR=${KODIR}
MKMODULESENV+= MACHINE_CPUARCH=${MACHINE_CPUARCH}
--zhXaljGHf11kAtnf--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20110531152654.GA42990>