[M3commit] CVS Update: cm3

Thu Jan 6 22:17:03 CET 2011

If I have a try/finally or lock in a loop, those lines aren't going to guaranteeably store the same values each time?

 - Jay

----------------------------------------
> Subject: Re: [M3commit] CVS Update: cm3
> From: hosking at cs.purdue.edu
> Date: Thu, 6 Jan 2011 16:00:08 -0500
> CC: m3commit at elegosoft.com
> To: jay.krell at cornell.edu
>
> In the code below there are no initializations.
>
> On Jan 6, 2011, at 3:51 PM, Jay K wrote:
>
> >
> > ps: I think there other non-ideal initializations here.
> > e.g.
> >
> >
> > TryFinStmt.m3:Compile2
> > (* declare and initialize the info record *)
> > frame := CG.Declare_local (M3ID.NoID, M3RT.EF2_SIZE, Target.Address.align,
> > CG.Type.Struct, 0, in_memory := TRUE,
> > up_level := FALSE, f := CG.Never);
> > CG.Load_procedure (p.handler.cg_proc);
> > CG.Store_addr (frame, M3RT.EF2_handler);
> > CG.Load_static_link (p.handler.cg_proc);
> > CG.Store_addr (frame, M3RT.EF2_frame);
> >
> >
> > Putting TRY/LOCK in loops probably repeatedly does the same initializations.
> > Granted, this is non-stack-walker code.
> >
> > Seems all bit a suspicious to me, though I'm pretty ignorant of m3front still..
> >
> > - Jay
> >
> > ----------------------------------------
> >> From: jay.krell at cornell.edu
> >> To: hosking at cs.purdue.edu
> >> CC: m3commit at elegosoft.com
> >> Subject: RE: [M3commit] CVS Update: cm3
> >> Date: Thu, 6 Jan 2011 20:48:56 +0000
> >>
> >>
> >> The same way as before. I think this operates at too low a level to get any automatic initialization.
> >>
> >> TryStmt.m3 and TryFinStmt.m3:
> >>
> >> frame := CG.Declare_local (M3ID.NoID, M3RT.EF1_SIZE, Target.Address.align,
> >> CG.Type.Struct, 0, in_memory := TRUE,
> >> up_level := FALSE, f := CG.Never);
> >>
> >> I agree though, this might not be ideal.
> >>
> >> - Jay
> >>
> >>
> >> ----------------------------------------
> >>> Subject: Re: [M3commit] CVS Update: cm3
> >>> From: hosking at cs.purdue.edu
> >>> Date: Thu, 6 Jan 2011 15:42:33 -0500
> >>> CC: m3commit at elegosoft.com
> >>> To: jay.krell at cornell.edu
> >>>
> >>> I don't understand what you mean by "initializes to NIL".
> >>> How are you creating the frame variable?
> >>> If you do it properly the language semantics will cause it be initialized to NIL automatically.
> >>>
> >>> On Jan 6, 2011, at 3:33 PM, Jay K wrote:
> >>>
> >>>>
> >>>> Ok.
> >>>> Do you know where to initialize the jmpbuf to NIL?
> >>>>
> >>>> I have a diff that "works" (ie: doesn't crash) and is *close* to correct,
> >>>> it checks for NIL and branches around the alloca for non-NIL, but it
> >>>> also initializes to NIL repeatedly, so no change effectively.
> >>>>
> >>>>
> >>>> Index: misc/Marker.m3
> >>>> ===================================================================
> >>>> RCS file: /usr/cvs/cm3/m3-sys/m3front/src/misc/Marker.m3,v
> >>>> retrieving revision 1.7
> >>>> diff -u -w -r1.7 Marker.m3
> >>>> --- misc/Marker.m3 5 Jan 2011 14:34:54 -0000 1.7
> >>>> +++ misc/Marker.m3 6 Jan 2011 20:32:00 -0000
> >>>> @@ -233,6 +233,7 @@
> >>>>
> >>>> PROCEDURE CaptureState (frame: CG.Var; handler: CG.Label) =
> >>>> VAR new: BOOLEAN;
> >>>> + label := CG.Next_label ();
> >>>> BEGIN
> >>>> (* int setjmp(void* ); *)
> >>>> IF (setjmp = NIL) THEN
> >>>> @@ -263,18 +264,25 @@
> >>>> Target.Word.cg_type, 0);
> >>>> END;
> >>>>
> >>>> + (* IF frame.jmpbuf = NIL THEN *)
> >>>> +
> >>>> + CG.Load_nil ();
> >>>> + CG.Load_addr (frame, M3RT.EF1_jmpbuf);
> >>>> + CG.If_compare (Target.Address.cg_type, CG.Cmp.NE, label, CG.Maybe);
> >>>> +
> >>>> (* frame.jmpbuf = alloca(Csetjmp__Jumpbuf_size); *)
> >>>> CG.Start_call_direct (alloca, 0, Target.Address.cg_type);
> >>>> CG.Load_int (Target.Word.cg_type, Jumpbuf_size);
> >>>> CG.Pop_param (Target.Word.cg_type);
> >>>> CG.Call_direct (alloca, Target.Address.cg_type);
> >>>> - CG.Store (frame, M3RT.EF1_jmpbuf, Target.Address.size, Target.Address.align,
> >>>> - Target.Address.cg_type);
> >>>> + CG.Store_addr (frame, M3RT.EF1_jmpbuf);
> >>>> +
> >>>> + (* END *)
> >>>> + CG.Set_label (label);
> >>>>
> >>>> (* setmp(frame.jmpbuf) *)
> >>>> CG.Start_call_direct (setjmp, 0, Target.Integer.cg_type);
> >>>> - CG.Load (frame, M3RT.EF1_jmpbuf, Target.Address.size, Target.Address.align,
> >>>> - Target.Address.cg_type);
> >>>> + CG.Load_addr (frame, M3RT.EF1_jmpbuf);
> >>>> CG.Pop_param (CG.Type.Addr);
> >>>> CG.Call_direct (setjmp, Target.Integer.cg_type);
> >>>> CG.If_true (handler, CG.Never);
> >>>> cvs diff: Diffing stmts
> >>>> Index: stmts/TryFinStmt.m3
> >>>> ===================================================================
> >>>> RCS file: /usr/cvs/cm3/m3-sys/m3front/src/stmts/TryFinStmt.m3,v
> >>>> retrieving revision 1.6
> >>>> diff -u -w -r1.6 TryFinStmt.m3
> >>>> --- stmts/TryFinStmt.m3 5 Jan 2011 14:34:54 -0000 1.6
> >>>> +++ stmts/TryFinStmt.m3 6 Jan 2011 20:32:00 -0000
> >>>> @@ -299,6 +299,10 @@
> >>>> CG.Load_nil ();
> >>>> CG.Store_addr (frame, M3RT.EF1_info + M3RT.EA_exception);
> >>>>
> >>>> + (* no jmpbuf yet (avoid repeated alloca in try within loop) *)
> >>>> + CG.Load_nil ();
> >>>> + CG.Store_addr (frame, M3RT.EF1_jmpbuf);
> >>>> +
> >>>> l := CG.Next_label (3);
> >>>> CG.Set_label (l, barrier := TRUE);
> >>>> Marker.PushFrame (frame, M3RT.HandlerClass.Finally);
> >>>> Index: stmts/TryStmt.m3
> >>>> ===================================================================
> >>>> RCS file: /usr/cvs/cm3/m3-sys/m3front/src/stmts/TryStmt.m3,v
> >>>> retrieving revision 1.3
> >>>> diff -u -w -r1.3 TryStmt.m3
> >>>> --- stmts/TryStmt.m3 5 Jan 2011 14:34:54 -0000 1.3
> >>>> +++ stmts/TryStmt.m3 6 Jan 2011 20:32:00 -0000
> >>>> @@ -10,7 +10,7 @@
> >>>>
> >>>> IMPORT M3, M3ID, CG, Variable, Scope, Exceptionz, Value, Error, Marker;
> >>>> IMPORT Type, Stmt, StmtRep, TryFinStmt, Token;
> >>>> -IMPORT Scanner, ESet, Target, M3RT, Tracer;
> >>>> +IMPORT Scanner, ESet, Target, M3RT, Tracer, IO;
> >>>> FROM Scanner IMPORT Match, MatchID, GetToken, Fail, cur;
> >>>>
> >>>> TYPE
> >>>> @@ -411,6 +411,10 @@
> >>>> CG.Store_addr (frame, M3RT.EF1_exception);
> >>>> ***********************************************)
> >>>>
> >>>> + (* no jmpbuf yet (avoid repeated alloca in try within loop) *)
> >>>> + CG.Load_nil ();
> >>>> + CG.Store_addr (frame, M3RT.EF1_jmpbuf);
> >>>> +
> >>>> IF (p.hasElse) THEN
> >>>> Marker.PushTryElse (l, l+1, frame);
> >>>> Marker.PushFrame (frame, M3RT.HandlerClass.ExceptElse);
> >>>>
> >>>>
> >>>> The set_label before one of the PushEFrames could be moved down a bit,
> >>>> to after the NIL initialization, and that'd fix some cases, but I think not all.
> >>>>
> >>>> Thanks,
> >>>> - Jay
> >>>>
> >>>>
> >>>> ----------------------------------------
> >>>>> Subject: Re: [M3commit] CVS Update: cm3
> >>>>> From: hosking at cs.purdue.edu
> >>>>> Date: Thu, 6 Jan 2011 14:11:04 -0500
> >>>>> CC: m3commit at elegosoft.com
> >>>>> To: jay.krell at cornell.edu
> >>>>>
> >>>>> At this point, we are trying to move away from the setjmp implementation to one that relies on unwind support, so I don't think the effort here is worthwhile.
> >>>>>
> >>>>> Antony Hosking | Associate Professor | Computer Science | Purdue University
> >>>>> 305 N. University Street | West Lafayette | IN 47907 | USA
> >>>>> Office +1 765 494 6001 | Mobile +1 765 427 5484
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> On Jan 6, 2011, at 2:00 PM, Jay K wrote:
> >>>>>
> >>>>>>
> >>>>>> I believe you can, but it'd take significant work in the frontend.
> >>>>>> The jmpbuf should identify merely which procedure/frame to return to.
> >>>>>> There would also be a volatile local integer, that gets altered at certain points through the function.
> >>>>>> When setjmp returns exceptionally, you'd switch on that integer to determine where to "really" go.
> >>>>>> This is analogous to how other systems work -- NT/x86 has a highly optimized frame based exception
> >>>>>> handling. Instead of a generic thread local, FS:0 is reserved to be the head of the linked list of frames.
> >>>>>> Instead of setjmp, the compiler pessimizes appropriately.
> >>>>>>
> >>>>>>
> >>>>>> So the result is that a function with one or more tries, or one or more locals with destructors,
> >>>>>> puts one node on the FS:0 list, and then mucks with the volatile local integer to indicate
> >>>>>> where in the function it is.
> >>>>>>
> >>>>>>
> >>>>>> If NT/x86 were inefficient more analogous to current Modula-3, it'd link/unlink in FS:0 more often.
> >>>>>>
> >>>>>>
> >>>>>> It is more work through, granted, I can understand that.
> >>>>>> And given that we have a much better option for many platforms, the payoff would be reduced.
> >>>>>>
> >>>>>>
> >>>>>> Anyway, I'm trying what you say, like for TRY within a loop.
> >>>>>>
> >>>>>>
> >>>>>> I should point out that alloca has an extra inefficiency vs. the previous approach.
> >>>>>> It aligns more. So it is using more stack than the other way.
> >>>>>> And it might pessimize codegen in other ways.
> >>>>>>
> >>>>>>
> >>>>>> The gcc code appears somewhat similar..I think the tables merely describe, again, which
> >>>>>> function/frame to return to, and that within the frame there is a local integer to determine
> >>>>>> more precisely what to do. I'm not sure. I saw mention of a switch.
> >>>>>>
> >>>>>>
> >>>>>> - Jay
> >>>>>>
> >>>>>> ________________________________
> >>>>>>> Subject: Re: [M3commit] CVS Update: cm3
> >>>>>>> From: hosking at cs.purdue.edu
> >>>>>>> Date: Thu, 6 Jan 2011 13:52:42 -0500
> >>>>>>> CC: m3commit at elegosoft.com
> >>>>>>> To: jay.krell at cornell.edu
> >>>>>>>
> >>>>>>> You can't have one jmpbuf per procedure. You need one per TRY scope,
> >>>>>>> since they can be nested.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> On Jan 6, 2011, at 11:35 AM, Jay K wrote:
> >>>>>>>
> >>>>>>> Hm. How do I single instance the "EF1"? The current code allocates a
> >>>>>>> local "EF1" for each try.
> >>>>>>> I guess, really, it is EF1, EF2, etc.
> >>>>>>> So there should be a separate local for the jmpbuf pointer, and store
> >>>>>>> it in each EF* block?
> >>>>>>> How do I make just one jmpbuf pointer? I couldn't easily figure out how
> >>>>>>> to in the front end, I need to read it more.
> >>>>>>>
> >>>>>>> something like:
> >>>>>>>
> >>>>>>> PROCEDURE F1() = BEGIN TRY1 do stuff1 TRY2 do stuff 2 TRY3 do stuff 3
> >>>>>>> END END END END F1;
> >>>>>>> =>
> >>>>>>>
> >>>>>>> void F1()
> >>>>>>> {
> >>>>>>> jmp_buf* jb = 0;
> >>>>>>> EF1 a,b,c;
> >>>>>>> setjmp(a.jmpbuf = jb ? jb : (jb = alloca(sizeof(jmp_buf))); // TRY1
> >>>>>>> do stuff 1...
> >>>>>>> setjmp(b.jmpbuf = jb ? jb : (jb = alloca(sizeof(jmp_buf))); // TRY2
> >>>>>>> do stuff 2...
> >>>>>>> setjmp(c.jmpbuf = jb ? jb : (jb = alloca(sizeof(jmp_buf))); // TRY3
> >>>>>>> do stuff 3...
> >>>>>>> }
> >>>>>>>
> >>>>>>> (The actual syntactic and semantic correctness of this code -- the
> >>>>>>> existance of the ternary operator, and that it only evaluates one side
> >>>>>>> or the other, and that assignment is expression..I quite like those
> >>>>>>> features....)
> >>>>>>>
> >>>>>>>
> >>>>>>> Still, something I can't pin down strikes me as too simple here.
> >>>>>>>
> >>>>>>>
> >>>>>>> If there is just one setjmp, and no integer(s) to keep track of
> >>>>>>> additional progress, you only ever know the last place you were in a
> >>>>>>> function.
> >>>>>>> That doesn't seem adequate.
> >>>>>>>
> >>>>>>>
> >>>>>>> What if a function raises an exception, catches it within itself, and
> >>>>>>> then raises something else, and then wants to catch that?
> >>>>>>> It won't know where to resume, right? It's just keep longjmping to the
> >>>>>>> same place.
> >>>>>>>
> >>>>>>>
> >>>>>>> In the Visual C++ runtime, there is "local unwind" and "global unwind".
> >>>>>>> "local unwind" is like, "within the same functin", "global unwind" is
> >>>>>>> across functions.
> >>>>>>> I think somehow that is related here.
> >>>>>>>
> >>>>>>>
> >>>>>>> e.g. how would you ensure forward progress in this:
> >>>>>>>
> >>>>>>>
> >>>>>>> EXCEPTION E1;
> >>>>>>> EXCEPTION E2;
> >>>>>>> EXCEPTION E3;
> >>>>>>>
> >>>>>>>
> >>>>>>> PROCEDURE F4() RAISES ANY =
> >>>>>>> CONST Function = "F4 ";
> >>>>>>> BEGIN
> >>>>>>> Put(Function & Int(Line())); NL();
> >>>>>>> TRY
> >>>>>>> Put(Function & Int(Line())); NL();
> >>>>>>> TRY
> >>>>>>> Put(Function & Int(Line())); NL();
> >>>>>>> TRY
> >>>>>>> Put(Function & Int(Line())); NL();
> >>>>>>> RAISE E1;
> >>>>>>> EXCEPT ELSE
> >>>>>>> RAISE E2;
> >>>>>>> END;
> >>>>>>> EXCEPT ELSE
> >>>>>>> RAISE E3;
> >>>>>>> END;
> >>>>>>> EXCEPT ELSE
> >>>>>>> END;
> >>>>>>> END F4;
> >>>>>>>
> >>>>>>>
> >>>>>>> Oddly in my test p251, the stack depth is not increased by TRY.
> >>>>>>>
> >>>>>>>
> >>>>>>> - Jay
> >>>>>>>
> >>>>>>> ________________________________
> >>>>>>> Subject: Re: [M3commit] CVS Update: cm3
> >>>>>>> From: hosking at cs.purdue.edu
> >>>>>>> Date: Thu, 6 Jan 2011 09:22:09 -0500
> >>>>>>> CC: m3commit at elegosoft.com
> >>>>>>> To: jay.krell at cornell.edu
> >>>>>>>
> >>>>>>> I am OK with what you have currently:
> >>>>>>>
> >>>>>>> At each TRY:
> >>>>>>>
> >>>>>>> 1. Check if a corresponding alloca block has been allocated by checking
> >>>>>>> if the corresponding local variable is NIL.
> >>>>>>> 2. If not, then alloca and save its pointer in the local variable
> >>>>>>> 3. Execute the try block.
> >>>>>>>
> >>>>>>> As you say, alloca should turn into an inline operation using the
> >>>>>>> compiler's builtin implementation of alloca.
> >>>>>>>
> >>>>>>> On Jan 6, 2011, at 1:02 AM, Jay K wrote:
> >>>>>>>
> >>>>>>>> Code size will suffer.
> >>>>>>>
> >>>>>>>
> >>>>>>> Indeed. Unoptimized code size does suffer a lot, in functions that use try.
> >>>>>>> Calling alloca, unoptimized, isn't small, and this adds n calls for n trys.
> >>>>>>> I thought it'd only be one call. I didn't realize our implementation
> >>>>>>> is as poor as it is, since a better but still
> >>>>>>> portable implementation doesn't seem too too difficult.
> >>>>>>>
> >>>>>>>
> >>>>>>> Can we maybe do the optimizations I indicate -- no more than one
> >>>>>>> setjmp/alloca/pushframe per function?
> >>>>>>> Using a local integer to record the position within the function?
> >>>>>>>
> >>>>>>>
> >>>>>>> Or just give me a week or few to get stack walking working and then
> >>>>>>> live the regression on other targets?
> >>>>>>> (NT386 isn't likely to get stack walking, though it *is* certainly
> >>>>>>> possible; NT does have a decent runtime here..)
> >>>>>>>
> >>>>>>>
> >>>>>>> It *is* nice to not have have the frontend know about jmpbuf size.
> >>>>>>>
> >>>>>>>
> >>>>>>> I looked into the "builtin_setjmp" stuff, but it can't be used so easily.
> >>>>>>> It doesn't work for intra-function jumps, only inter-function.
> >>>>>>>
> >>>>>>>
> >>>>>>> - Jay
> >>>>>>>
> >>>>>>>
> >>>>>>> ________________________________
> >>>>>>> From: jay.krell at cornell.edu
> >>>>>>> To: hosking at cs.purdue.edu
> >>>>>>> CC: m3commit at elegosoft.com
> >>>>>>> Subject: RE: [M3commit] CVS Update: cm3
> >>>>>>> Date: Thu, 6 Jan 2011 04:52:33 +0000
> >>>>>>>
> >>>>>>> Ah..I'm doing more comparisons of release vs. head...but..I guess your
> >>>>>>> point is, you'd rather have n locals, which the backend automatically
> >>>>>>> merges, than n calls to alloca?
> >>>>>>> It's not a huge difference -- there are still going to be n calls to
> >>>>>>> setjmp and n calls to pthread_getspecific.
> >>>>>>> The alloca calls will be dwarfed.
> >>>>>>> Code size will suffer.
> >>>>>>>
> >>>>>>>
> >>>>>>> And, even so, there are plenty of optimizations to be had, even if
> >>>>>>> setjmp/pthread_getspecific is used.
> >>>>>>>
> >>>>>>>
> >>>>>>> - It could make a maximum of one call to setjmp/pthread_getspecific
> >>>>>>> per function
> >>>>>>> - The calls to alloca could be merged. The frontend could keep track
> >>>>>>> of how many calls it makes per function,
> >>>>>>> issue a multiplication, and offset each jmpbuf. It is a tradeoff.
> >>>>>>>
> >>>>>>>
> >>>>>>> So, yes, given my current understanding, it is progress.
> >>>>>>> The target-dependence is not worth it, imho.
> >>>>>>> I'll still do some comparisons to release.
> >>>>>>>
> >>>>>>>
> >>>>>>> I'll still be looking into using the gcc unwinder relatively soon.
> >>>>>>>
> >>>>>>>
> >>>>>>> - Jay
> >>>>>>>
> >>>>>>>
> >>>>>>> ________________________________
> >>>>>>> Subject: Re: [M3commit] CVS Update: cm3
> >>>>>>> From: hosking at cs.purdue.edu
> >>>>>>> Date: Wed, 5 Jan 2011 21:14:17 -0500
> >>>>>>> CC: m3commit at elegosoft.com
> >>>>>>> To: jay.krell at cornell.edu
> >>>>>>>
> >>>>>>> On Jan 5, 2011, at 9:08 PM, Jay K wrote:
> >>>>>>>
> >>>>>>> Tony, um..well, um.. first, isn't that how it already worked maybe?
> >>>>>>> Declaring a new local EF1 for each TRY? It looks like it.
> >>>>>>> I'll do more testing.
> >>>>>>>
> >>>>>>> Yes, it did. I assume you simply have a local variable for each TRY
> >>>>>>> block that is a pointer now instead of a jmp_buf. Should be OK.
> >>>>>>>
> >>>>>>>
> >>>>>>> So the additional inefficiency is multiplied the same as the rest of
> >>>>>>> the preexisting inefficiency.
> >>>>>>> And the preexisting inefficiency is way more than the increase.
> >>>>>>>
> >>>>>>> And second, either way, it could be better.
> >>>>>>>
> >>>>>>> Basically, the model should be, that if a function has any try or lock,
> >>>>>>> it calls setjmp once.
> >>>>>>> And then, it should have one volatile integer, that in a sense
> >>>>>>> represents the line number.
> >>>>>>> But not really. It's like, every time you cross a TRY, the integer is
> >>>>>>> incremented, every time you
> >>>>>>> cross a finally or unlock, the integer is decremented. Or rather, the
> >>>>>>> value can be stored.
> >>>>>>> And then there is a maximum of one one handler per function, it
> >>>>>>> switches on the integer
> >>>>>>> to decide where it got into the function and what it should do.
> >>>>>>>
> >>>>>>> This is how other compilers work and it is a fairly simple sensible approach.
> >>>>>>>
> >>>>>>> - Jay
> >>>>>>>
> >>>>>>>
> >>>>>>> ________________________________
> >>>>>>> Subject: Re: [M3commit] CVS Update: cm3
> >>>>>>> From: hosking at cs.purdue.edu
> >>>>>>> Date: Wed, 5 Jan 2011 20:49:24 -0500
> >>>>>>> CC: m3commit at elegosoft.com
> >>>>>>> To: jay.krell at cornell.edu
> >>>>>>>
> >>>>>>> Note that you need a different jmpbuf for each nested TRY!
> >>>>>>>
> >>>>>>> Antony Hosking | Associate Professor | Computer Science | Purdue University
> >>>>>>> 305 N. University Street | West Lafayette | IN 47907 | USA
> >>>>>>> Office +1 765 494 6001 | Mobile +1 765 427 5484
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> On Jan 5, 2011, at 8:33 PM, Jay K wrote:
> >>>>>>>
> >>>>>>> oops, that's not how I thought it worked. I'll do more testing and fix
> >>>>>>> it -- check for NIL.
> >>>>>>>
> >>>>>>> - Jay
> >>>>>>>
> >>>>>>> ________________________________
> >>>>>>> Subject: Re: [M3commit] CVS Update: cm3
> >>>>>>> From: hosking at cs.purdue.edu
> >>>>>>> Date: Wed, 5 Jan 2011 20:23:09 -0500
> >>>>>>> CC: m3commit at elegosoft.com
> >>>>>>> To: jay.krell at cornell.edu
> >>>>>>>
> >>>>>>> Ah, yes, I guess you need a different jmpbuf for each TRY. But now you
> >>>>>>> are allocating on every TRY where previously the storage was statically
> >>>>>>> allocated. Do you really think this is progress?
> >>>>>>>
> >>>>>>> On Jan 5, 2011, at 5:40 PM, Jay K wrote:
> >>>>>>>
> >>>>>>> I've back with full keyboard if more explanation needed. The diff is
> >>>>>>> actually fairly small to read.
> >>>>>>> I understand it is definitely less efficient, a few more instructions
> >>>>>>> for every try/lock.
> >>>>>>> No extra function call, at least with gcc backend.
> >>>>>>> I haven't tested NT386 yet. Odds are so/so that it works -- the change
> >>>>>>> is written so that it should work
> >>>>>>> but I have to test it to be sure, will to roughly tonight. And there
> >>>>>>> probably is a function call there.
> >>>>>>>
> >>>>>>> - Jay
> >>>>>>>
> >>>>>>> ________________________________
> >>>>>>> From: jay.krell at cornell.edu
> >>>>>>> To: hosking at cs.purdue.edu
> >>>>>>> Date: Wed, 5 Jan 2011 20:44:08 +0000
> >>>>>>> CC: m3commit at elegosoft.com
> >>>>>>> Subject: Re: [M3commit] CVS Update: cm3
> >>>>>>>
> >>>>>>> I only have phone right now. I think it is fairly clear: the jumpbuf in
> >>>>>>> EF1 is now allocated with alloca, and a pointer stored. It is
> >>>>>>> definitely a bit less efficient, but the significant advantage is
> >>>>>>> frontend no longer needs to know the size or alignment of a jumpbuf.
> >>>>>>>
> >>>>>>>
> >>>>>>> As well, there is no longer the problem regarding jumpbuf aligned to
> >>>>>>> more than 64 bits. I at least checked on Linux/PowerPC and alloca seems
> >>>>>>> to align to 16 bytes. I don't have an HPUX machine currently to see if
> >>>>>>> the problem is addressed there.
> >>>>>>>
> >>>>>>>
> >>>>>>> The inefficiency of course can be dramatically mitigated via a stack
> >>>>>>> walker. I wanted to do this first though, while more targets using
> >>>>>>> setjmp.
> >>>>>>>
> >>>>>>> - Jay/phone
> >>>>>>>
> >>>>>>> ________________________________
> >>>>>>> Subject: Re: [M3commit] CVS Update: cm3
> >>>>>>> From: hosking at cs.purdue.edu
> >>>>>>> Date: Wed, 5 Jan 2011 13:35:59 -0500
> >>>>>>> CC: jkrell at elego.de; m3commit at elegosoft.com
> >>>>>>> To: jay.krell at cornell.edu
> >>>>>>>
> >>>>>>> Can you provide a more descriptive checkin comment? I don't know what
> >>>>>>> has been done here without diving into the diff.
> >>>>>>>
> >>>>>>> Antony Hosking | Associate Professor | Computer Science | Purdue University
> >>>>>>> 305 N. University Street | West Lafayette | IN 47907 | USA
> >>>>>>> Office +1 765 494 6001 | Mobile +1 765 427 5484
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> On Jan 5, 2011, at 9:37 AM, Jay K wrote:
> >>>>>>>
> >>>>>>> diff attached
> >>>>>>>
> >>>>>>>> Date: Wed, 5 Jan 2011 15:34:55 +0000
> >>>>>>>> To: m3commit at elegosoft.com
> >>>>>>>> From: jkrell at elego.de
> >>>>>>>> Subject: [M3commit] CVS Update: cm3
> >>>>>>>>
> >>>>>>>> CVSROOT: /usr/cvs
> >>>>>>>> Changes by: jkrell at birch. 11/01/05 15:34:55
> >>>>>>>>
> >>>>>>>> Modified files:
> >>>>>>>> cm3/m3-libs/m3core/src/C/Common/: Csetjmp.i3
> >>>>>>>> cm3/m3-libs/m3core/src/C/I386_CYGWIN/: Csetjmp.i3
> >>>>>>>> cm3/m3-libs/m3core/src/C/I386_MINGW/: Csetjmp.i3
> >>>>>>>> cm3/m3-libs/m3core/src/C/I386_NT/: Csetjmp.i3
> >>>>>>>> cm3/m3-libs/m3core/src/C/NT386/: Csetjmp.i3
> >>>>>>>> cm3/m3-libs/m3core/src/runtime/ex_frame/: RTExFrame.m3
> >>>>>>>> cm3/m3-libs/m3core/src/unix/Common/: Uconstants.c
> >>>>>>>> cm3/m3-sys/m3cc/gcc/gcc/m3cg/: parse.c
> >>>>>>>> cm3/m3-sys/m3front/src/misc/: Marker.m3
> >>>>>>>> cm3/m3-sys/m3front/src/stmts/: TryFinStmt.m3 TryStmt.m3
> >>>>>>>> cm3/m3-sys/m3middle/src/: M3RT.i3 M3RT.m3 Target.i3 Target.m3
> >>>>>>>>
> >>>>>>>> Log message:
> >>>>>>>> use: extern INTEGER Csetjmp__Jumpbuf_size /* = sizeof(jmp_buf);
> >>>>>>>> alloca(Csetjmp__Jumpbuf_size)
> >>>>>>>>
> >>>>>>>> to allocate jmp_buf
> >>>>>>>>
> >>>>>>>> - eliminates a large swath of target-dependent code
> >>>>>>>> - allows for covering up the inability to declare
> >>>>>>>> types with alignment > 64 bits
> >>>>>>>>
> >>>>>>>> It is, granted, a little bit slower, in an already prety slow path.
> >>>>>>>> Note that alloca isn't actually a function call, at least with gcc backend.
> >>>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>
> >>>>
> >>>
> >>
> >
>