http://d.puremagic.com/issues/show_bug.cgi?id=2773

           Summary: problem compiling a big program with -O -inline -release
           Product: D
           Version: 1.041
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: regression
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: aliloko@gmail.com


When compiling with dmd -O -inline -release, dmd hangs up and I get the
following error message.
I did'nt succeeded in isolating the problem. The bug appear only with all three
arguments (-O -inline -release).


Internal Error : ..\ztc\go.c 243

The corresponding line in the back-end source code is :

243 :    assert(++iter < 200);  /* infinite loop check           */


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------- Comment #1 from bugzilla@digitalmars.com  2009-04-01 14:00 -------
I cannot do anything with this without a reproducible example.

But I suggest that to work around, split your large function into a couple smaller ones.


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------- Comment #2 from unknown@simplemachines.org  2009-04-03 14:10 -------
Created an attachment (id=312)
 --> (http://d.puremagic.com/issues/attachment.cgi?id=312&action=view)
Reduced test case.

Attached is a reduced test case (can't spend time on it now but wanted to
attach this.)

Compile with:

dmd -O -inline -release -c 2773_reduced.d

Bug occurs in DMD 1.041 and DMD 2.026, most likely in 2.027 as well.

-[Unknown]


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------- Comment #3 from gide@nwawudu.com  2009-04-03 16:23 -------
The error is different in DMD 2.027.

dmd -O -inline -release -c 2773_reduced.d
Internal error: ..\ztc\go.c 243


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------- Comment #4 from unknown@simplemachines.org  2009-04-03 21:22 -------
Created an attachment (id=313)
 --> (http://d.puremagic.com/issues/attachment.cgi?id=313&action=view)
Workaround patch: make endless iteration not an error.

Please note: this patch does not fix this bug.

I suggest dropping the assert for iter, and instead treating it the same as the clock timeout.  While this makes this class of bug less discoverable, I propose that it's better that it compiles - at least some functions will be optimized.

Regarding this bug - it keeps moving an equation to optimize it, so each time the loop runs it's got more changes.  Unfortunately, the innards of the backend are still a bit beyond me, so I can't see why.

Note that the second call to pointer.clear() can be a call to another method,
on the same struct, as long as that method does something (anything.)

Also, reducing the size of the static array below 3 (or making it dynamic) solves it, but a bigger one still dies.  Changing the code within clear() to any other operation also solves it.  And the struct has to be within a class, returned from a method.

-[Unknown]


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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|ICE(go.c) compiling a big   |ICE(go.c) array assignment
                   |program with -O -inline     |through a pointer, only
                   |-release                    |with -O.




--- Comment #5 from Don <clugdbug@yahoo.com.au>  2009-05-20 06:49:00 PDT ---
Here's a slightly reduced test case, which only requires -O (doesn't need -inline -release), and ICEs on both D1 and D2. On D2, you still get an ICE if you remove all references to the class, and just set S2773* pointer = &dat.

struct S2773{
  int[4] data;
}

S2773 dat;

class C2773 {
  S2773* get()    {  return &dat;  }
}

void main()
{
  C2773 inst = null;
  S2773* pointer = inst.get();
  pointer.data[] = 0;
  pointer.data[] = 0;
}

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|regression                  |critical




--- Comment #6 from Don <clugdbug@yahoo.com.au>  2009-08-31 08:23:36 PDT ---
This isn't a regression. It failed on DMD1.022 as well, which was released in mid-2007, almost 2 years before this bug report.

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--- Comment #7 from Don <clugdbug@yahoo.com.au> 2009-10-05 03:12:06 PDT ---
Even simpler test case, this one fails on both D1.033 and 1.048.
int[4]* get()    {  return null; }

void main()
{
  int[4]* p = get();
  (*p)[] = 0;
  (*p)[] = 0;
}

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch


--- Comment #8 from Don <clugdbug@yahoo.com.au> 2009-10-06 00:17:14 PDT ---
An even simpler test case shows something interesting: it happens only when there's an array assignment of 0, followed by another use of the same variable. An array assignment to 0 is an OPmemset operation in the backend.

int* get()  {  return null; }
void main(){
  int* p = get();
  p[0..3] = 0; // must be = 0!! Doesn't happen with any other number.
  p[0] = 7;
}

ANALYSIS:
This is an OPmemset fight! In the optimisation loop, there's a localize step
which rearranges the assignment, and there's a canonicalize step which sets it
back the way it was before....

cgelem.c,  elmemxxx() line 702 replaces ((e op= v) op e2) with ((e op=v), (e op
e2))
ie,  (p = get()), p) memset 0.   ---> ((p = get()), p memset 0.

glocal.c,  local_exp() replaces
p = get(); p memset 0; ---> (p = get(), p) memset 0

So it just keeps going round in circles.
The fight can be broken up by changing cgelem.c elmemxxx() line 701
to avoid doing the first replacement:

-            if (e1->Eoper == OPcomma || OTassign(e1->Eoper))
+            if (e1->Eoper == OPcomma)

This probably isn't correct, there may be somewhere this particular canonicalisation is important. But without the DMC test suite, I can't tell. (Note that the comments in the code only refer to the OPcomma transformation, not the assignment one, so I presume the assignment was a later addition).

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


--- Comment #9 from Walter Bright <bugzilla@digitalmars.com> 2009-10-13 14:10:07 PDT ---
Fixed dmd 1.049 and 2.034

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