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Re: [PATCH] Re-use cc1-checksum.c for stage-final

From: Richard Biener <rguenther at suse dot de>
To: Jeff Law <law at redhat dot com>
Cc: gcc-patches at gcc dot gnu dot org
Date: Tue, 3 May 2016 12:32:25 +0200 (CEST)
Subject: Re: [PATCH] Re-use cc1-checksum.c for stage-final
Authentication-results: sourceware.org; auth=none
References: <alpine dot LSU dot 2 dot 11 dot 1604281043180 dot 13384 at t29 dot fhfr dot qr> <e4aa1967-6af2-e6cf-aa1e-632e9f41a097 at redhat dot com> <alpine dot LSU dot 2 dot 11 dot 1604291325310 dot 13384 at t29 dot fhfr dot qr> <6169754e-569f-38b1-53e6-4d0248dda968 at redhat dot com> <alpine dot LSU dot 2 dot 11 dot 1605031016490 dot 13384 at t29 dot fhfr dot qr>

On Tue, 3 May 2016, Richard Biener wrote:

> On Mon, 2 May 2016, Jeff Law wrote:
> 
> > On 04/29/2016 05:36 AM, Richard Biener wrote:
> > > On Thu, 28 Apr 2016, Jeff Law wrote:
> > > 
> > > > On 04/28/2016 02:49 AM, Richard Biener wrote:
> > > > > 
> > > > > The following prototype patch re-uses cc1-checksum.c from the
> > > > > previous stage when compiling stage-final.  This eventually
> > > > > allows to compare cc1 from the last two stages to fix the
> > > > > lack of a true comparison when doing LTO bootstrap (it
> > > > > compiles LTO bytecode from the compile-stage there, not the
> > > > > final optimization result).
> > > > > 
> > > > > Bootstrapped on x86_64-unknown-linux-gnu.
> > > > > 
> > > > > When stripping gcc/cc1 and prev-gcc/cc1 after the bootstrap
> > > > > they now compare identical (with LTO bootstrap it should
> > > > > not require stripping as that doesn't do a bootstrap-debug AFAIK).
> > > > > 
> > > > > Is sth like this acceptable?  (consider it also done for
> > > > > cp/Make-lang.in)
> > > > > 
> > > > > In theory we can compare all stage1 languages but I guess comparing
> > > > > the required ones for a LTO bootstrap, cc1, cc1plus and lto1 would
> > > > > be sufficient (or even just comparing one binary in which case
> > > > > comparing lto1 would not require any patches).
> > > > > 
> > > > > This also gets rid of the annoying warning that cc1-checksum.o
> > > > > differs (obviously).
> > > > > 
> > > > > Thanks,
> > > > > Richard.
> > > > > 
> > > > > 2016-04-28  Richard Biener  <rguenther@suse.de>
> > > > > 
> > > > > 	c/
> > > > > 	* Make-lang.in (cc1-checksum.c): For stage-final re-use
> > > > > 	the checksum from the previous stage.
> > > > I won't object if you add a comment into the fragment indicating why
> > > > you're
> > > > doing this.
> > > 
> > > So the following is a complete patch (not considering people may
> > > add objc or obj-c++ to stage1 languages).  Build with --disable-bootstrap,
> > > bootstrapped and profilebootstrapped with verifying it works as
> > > intended (looks like we don't compare with profiledbootstrap - huh,
> > > we're building stagefeedback only once)
> > > 
> > > Ok for trunk?
> > > 
> > > Step 2 will now be to figure out how to also compare cc1 (for example)
> > > when using bootstrap-lto ... (we don't want to do this unconditionally
> > > as it is a waste of time when the objects are not only LTO bytecode).
> > > 
> > > Thanks,
> > > Richard.
> > > 
> > > 2016-04-29  Richard Biener  <rguenther@suse.de>
> > > 
> > > 	c/
> > > 	* Make-lang.in (cc1-checksum.c): For stage-final re-use
> > > 	the checksum from the previous stage.
> > > 
> > > 	cp/
> > > 	* Make-lang.in (cc1plus-checksum.c): For stage-final re-use
> > > 	the checksum from the previous stage.
> > LGTM.
> > jeff
> 
> Thanks - applied as rev. 235804.
> 
> I'll now play with some way to add additional compare objects.  Thinking
> of adding sth like
> 
> EXTRA_COMPARE_OBJS = lto1 cc1 cc1plus
> 
> to bootstrap-lto.mk for example.

To my surprise this works.

LTO bootstrapped on x86_64-unknown-linux-gnu - I've added an additional
echo comparing $$f1 $$f2 which then shows

...
comparing /abuild/rguenther/obj/stage2-zlib/libz_a-inftrees.o 
/abuild/rguenther/obj/stage3-zlib/libz_a-inftrees.o
comparing /abuild/rguenther/obj/stage2-cc1 
/abuild/rguenther/obj/stage3-cc1
comparing /abuild/rguenther/obj/stage2-cc1plus 
/abuild/rguenther/obj/stage3-cc1plus
comparing /abuild/rguenther/obj/stage2-lto1 
/abuild/rguenther/obj/stage3-lto1
Comparison successful.

Ok for trunk?  This probably slows down the compare phase for
LTO bootstrap a bit (and LTO IL of the .o files is still compared).
I'm also not 100% sure that what works on .o files works on
executables on all targets (hmm, and I suppose I might miss
some exec-suffix?  Ah, there is $(exeext) but not available in
the toplevel makefile yet.).

Thanks,
Richard.

2016-05-03  Richard Biener  <rguenther@suse.de>

	* Makefile.tpl: Also compare EXTRA_COMPARE_OBJS.
	* Makefile.in: Regenerate.
	
	config/
	* bootstrap-lto.mk: Add cc1, cc1plus and lto1 to EXTRA_COMPARE_OBJS.

Index: Makefile.tpl
===================================================================
*** Makefile.tpl	(revision 235804)
--- Makefile.tpl	(working copy)
*************** do-clean: clean-stage[+id+]
*** 1630,1636 ****
          sed=`echo stage[+id+] | sed 's,^stage,,;s,.,.,g'`; \
  	files=`find stage[+id+]-* -name "*$(objext)" -print | \
  		 sed -n s,^stage$$sed-,,p`; \
! 	for file in $${files}; do \
  	  f1=$$r/stage[+prev+]-$$file; f2=$$r/stage[+id+]-$$file; \
  	  if test ! -f $$f1; then continue; fi; \
  	  $(do-[+compare-target+]) > /dev/null 2>&1; \
--- 1630,1636 ----
          sed=`echo stage[+id+] | sed 's,^stage,,;s,.,.,g'`; \
  	files=`find stage[+id+]-* -name "*$(objext)" -print | \
  		 sed -n s,^stage$$sed-,,p`; \
! 	for file in $${files} $(EXTRA_COMPARE_OBJS); do \
  	  f1=$$r/stage[+prev+]-$$file; f2=$$r/stage[+id+]-$$file; \
  	  if test ! -f $$f1; then continue; fi; \
  	  $(do-[+compare-target+]) > /dev/null 2>&1; \
Index: config/bootstrap-lto.mk
===================================================================
*** config/bootstrap-lto.mk	(revision 235804)
--- config/bootstrap-lto.mk	(working copy)
*************** LTO_RANLIB = $$r/$(HOST_SUBDIR)/prev-gcc
*** 11,13 ****
--- 11,15 ----
  LTO_EXPORTS = AR="$(LTO_AR)"; export AR; \
  	      RANLIB="$(LTO_RANLIB)"; export RANLIB;
  LTO_FLAGS_TO_PASS = AR="$(LTO_AR)" RANLIB="$(LTO_RANLIB)"
+ 
+ EXTRA_COMPARE_OBJS = cc1 cc1plus lto1
Index: Makefile.in
===================================================================
*** Makefile.in	(revision 235804)
--- Makefile.in	(working copy)
*************** compare:
*** 48785,48791 ****
          sed=`echo stage3 | sed 's,^stage,,;s,.,.,g'`; \
  	files=`find stage3-* -name "*$(objext)" -print | \
  		 sed -n s,^stage$$sed-,,p`; \
! 	for file in $${files}; do \
  	  f1=$$r/stage2-$$file; f2=$$r/stage3-$$file; \
  	  if test ! -f $$f1; then continue; fi; \
  	  $(do-compare) > /dev/null 2>&1; \
--- 48785,48791 ----
          sed=`echo stage3 | sed 's,^stage,,;s,.,.,g'`; \
  	files=`find stage3-* -name "*$(objext)" -print | \
  		 sed -n s,^stage$$sed-,,p`; \
! 	for file in $${files} $(EXTRA_COMPARE_OBJS); do \
  	  f1=$$r/stage2-$$file; f2=$$r/stage3-$$file; \
  	  if test ! -f $$f1; then continue; fi; \
  	  $(do-compare) > /dev/null 2>&1; \
*************** compare3:
*** 49183,49189 ****
          sed=`echo stage4 | sed 's,^stage,,;s,.,.,g'`; \
  	files=`find stage4-* -name "*$(objext)" -print | \
  		 sed -n s,^stage$$sed-,,p`; \
! 	for file in $${files}; do \
  	  f1=$$r/stage3-$$file; f2=$$r/stage4-$$file; \
  	  if test ! -f $$f1; then continue; fi; \
  	  $(do-compare3) > /dev/null 2>&1; \
--- 49183,49189 ----
          sed=`echo stage4 | sed 's,^stage,,;s,.,.,g'`; \
  	files=`find stage4-* -name "*$(objext)" -print | \
  		 sed -n s,^stage$$sed-,,p`; \
! 	for file in $${files} $(EXTRA_COMPARE_OBJS); do \
  	  f1=$$r/stage3-$$file; f2=$$r/stage4-$$file; \
  	  if test ! -f $$f1; then continue; fi; \
  	  $(do-compare3) > /dev/null 2>&1; \

Follow-Ups:
- Re: [PATCH] Re-use cc1-checksum.c for stage-final
  - From: Jeff Law

References:
- Re: [PATCH] Re-use cc1-checksum.c for stage-final
  - From: Jeff Law
- Re: [PATCH] Re-use cc1-checksum.c for stage-final
  - From: Richard Biener

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