[M3commit] CVS Update: cm3

[Tony Hosking]

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.
>>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>> 
>>>>> 
>>>> 
>>> 
>> 
>