| Summary: | [4.2 Regression] VRP ICE in compare_names | ||
|---|---|---|---|
| Product: | gcc | Reporter: | kargls |
| Component: | tree-optimization | Assignee: | Richard Biener <rguenth> |
| Status: | RESOLVED FIXED | ||
| Severity: | critical | CC: | dnovillo, fang, gcc-bugs, pinskia, rguenth |
| Priority: | P3 | Keywords: | ice-on-valid-code |
| Version: | 4.2.0 | ||
| Target Milestone: | 4.2.0 | ||
| Host: | Target: | ||
| Build: | Known to work: | 4.1.2 | |
| Known to fail: | 4.2.0 | Last reconfirmed: | 2006-10-13 10:38:52 |
| Bug Depends on: | |||
| Bug Blocks: | 31698 | ||
C testcase:
void f(int *n, int *m)
{
int i;
int ubound0;
int ubound1;
int stride2;
int offset3;
int size4;
int j;
int ubound5;
int size6;
int D919;
__SIZE_TYPE__ D920;
int D921;
unsigned int D922;
__SIZE_TYPE__ D923;
unsigned int D924;
ubound0 = *m;
stride2 = ubound0;
ubound1 = *n;
size4 = stride2 * ubound1;
D922 = size4 - 1;
int (*abc)[D922];
abc = _gfortran_internal_malloc (size4 * 4);
offset3 = ~stride2;
ubound5 = *n;
size6 = ubound5;
D919 = size6 - 1;
int (*xsd)[D919];
xsd = _gfortran_internal_malloc (size6 * 4);
i = 1;
if (i <= 2)
{
while (1)
{
{
_Bool D918;
j = 1;
if (j <= 3)
{
while (1)
{
{
_Bool D917;
if (i != j)
{
if (__builtin_expect (ubound0 <= 0, 0))
{
__builtin_abort ();
}
else
{
(void) 0;
}
if (__builtin_expect (ubound1 <= 0, 0))
{
__builtin_abort ();
}
else
{
(void) 0;
}
(*abc)[stride2 + offset3 + 1] = 0;
}
else
{
{
int D916;
if (__builtin_expect (ubound0 <= 0, 0))
{
__builtin_abort ();
}
else
{
(void) 0;
}
D916 = j;
if (__builtin_expect (D916 <= 0, 0))
{
__builtin_abort ();
}
else
{
(void) 0;
}
if (__builtin_expect (D916 > ubound1, 0))
{
__builtin_abort ();
}
else
{
(void) 0;
}
if (__builtin_expect (ubound5 <= 0, 0))
{
__builtin_abort ();
}
else
{
(void) 0;
}
(*abc)[D916 * stride2 + offset3 + 1] = (*xsd)[0];
}
}
D917 = j == 3;
j = j + 1;
if (D917) break; else (void) 0;
}
}
}
else
{
(void) 0;
}
// L4:;
D918 = i == 2;
i = i + 1;
if (D918) break; else (void) 0;
}
}
}
else
{
(void) 0;
}
//L2:;
_gfortran_internal_free ((void *) xsd);
_gfortran_internal_free ((void *) abc);
}
here is a shorter testcase:
void f(void)
{
int i, ubound1, j, ubound5;
int (*abc)[3];
i = 1;
while (1)
{
if (j <= 3)
while (1)
{
_Bool D917;
if (i != j)
{
if (__builtin_expect (ubound1 <= 0, 0))
__builtin_abort ();
(*abc)[1] = 0;
}
else
{
int D916;
D916 = j;
if (__builtin_expect (D916 > ubound1, 0))
__builtin_abort ();
if (__builtin_expect (ubound5 <= 0, 0))
__builtin_abort ();
}
j = j + 1;
if (D917)
break;
}
i = i + 1;
}
}
Slightly less undefined, ICEs with -O -ftree-vrp -funswitch-loops:
void f(_Bool D917, int j0, int ubound1, int ubound5)
{
int i, j = j0;
int (*abc)[3];
i = 1;
while (1)
{
if (j <= 3)
while (1)
{
if (i != j)
{
if (ubound1 <= 0)
return;
(*abc)[1] = 0;
}
else
{
if (j > ubound1)
return;
if (ubound5 <= 0)
return;
}
j = j + 1;
if (D917)
break;
}
i = i + 1;
}
}
We end up comparing (GT_EXPR) i_92 with ubound1_111 which have the following value ranges and equivalences:
i_92: [1, 3] EQUIVALENCES: { i_1 j_2 i_67 j_70 } (4 elements)
i_1: ~[0, 0] EQUIVALENCES: { } (0 elements)
j_2: VARYING
i_67: [1, ubound1_8] EQUIVALENCES: { i_1 } (1 elements)
j_70: [-INF, 3] EQUIVALENCES: { j_2 } (1 elements)
ubound1_111: [-INF, 0] EQUIVALENCES: { ubound1_8 ubound1_112 } (2 elements)
ubound1_8: VARYING
ubound1_112: [i_67, +INF] EQUIVALENCES: { ubound1_8 } (1 elements)
i_67 > ubound1_8 ([1, ubound1_8] > [ubound1_8, ubound1_8]) is false
i_67 > ubound1_111 ([1, ubound1_8] > [-INF, 0]) is true
i_92 > ubound1_111 ([1, 3] > [-INF, 0]) is true
So we have a cross-equivalency set inconsistency.
It looks like we would need to recurse down into symbolic ranges in fix_equivalence_set, which would be far too costly. So a conservative fix for 4.2 is to just not record symbolic equivalencies at all. I wonder if there is a better way to deal with these issues than fix_equivalence_set though. I have a patch to get rid of that beast completely. Subject: Bug number PR29446 A patch for this bug has been added to the patch tracker. The mailing list url for the patch is http://gcc.gnu.org/ml/gcc-patches/2006-10/msg00698.html Subject: Bug 29446 Author: rguenth Date: Fri Oct 13 20:09:10 2006 New Revision: 117705 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=117705 Log: 2006-10-13 Richard Guenther <rguenther@suse.de> PR tree-optimization/29446 * tree-vrp.c (fix_equivalence_set): Remove. (extract_range_from_assert): Do not call fix_equivalence_set. (debug_value_range): Print a newline. (compare_name_with_value): For equivalence sets with inconsistent value ranges conservatively bail out. (compare_names): Likewise. * gcc.dg/torture/pr29446.c: New testcase. Added: trunk/gcc/testsuite/gcc.dg/torture/pr29446.c Modified: trunk/gcc/ChangeLog trunk/gcc/testsuite/ChangeLog trunk/gcc/tree-vrp.c Fixed. Subject: Bug 29446 Author: rguenth Date: Wed Apr 25 17:10:31 2007 New Revision: 124158 URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=124158 Log: 2007-04-25 Richard Guenther <rguenther@suse.de> PR tree-optimization/31698 * g++.dg/other/pr31698.C: New testcase. Backport from mainline: 2006-10-13 Richard Guenther <rguenther@suse.de> PR tree-optimization/29446 * tree-vrp.c (fix_equivalence_set): Remove. (extract_range_from_assert): Do not call fix_equivalence_set. (debug_value_range): Print a newline. (compare_name_with_value): For equivalence sets with inconsistent value ranges conservatively bail out. (compare_names): Likewise. * gcc.dg/torture/pr29446.c: New testcase. Added: branches/gcc-4_1-branch/gcc/testsuite/g++.dg/other/pr31698.C branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/torture/pr29446.c - copied unchanged from r117705, trunk/gcc/testsuite/gcc.dg/torture/pr29446.c Modified: branches/gcc-4_1-branch/gcc/ChangeLog branches/gcc-4_1-branch/gcc/testsuite/ChangeLog branches/gcc-4_1-branch/gcc/tree-vrp.c |
troutmask:kargl[206] gfc -m32 -O3 -fbounds-check -c vrp.f90 vrp.f90: In function 'abc': vrp.f90:1: internal compiler error: in compare_names, at tree-vrp.c:3645 The Fortran code is function abc(n) integer :: xsd(n), abc(size(xsd),n), i, j, n do i=1,2 do j=1,3 if (i /= j) then abc(1,1) = 0 else abc(1,j) = xsd(1) end if end do end do end function abc