[Bug rtl-optimization/40924] [4.4 Regression] miscompiles with -03 (seemingly related to attribute may_alias)
--- Comment #6 from jakub at gcc dot gnu dot org 2009-08-05 12:36 --- Subject: Bug 40924 Author: jakub Date: Wed Aug 5 12:36:34 2009 New Revision: 150483 URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=150483 Log: PR rtl-optimization/40924 * dse.c (canon_address): Before calling cselib_expand_value_rtx make sure canon_rtx (mem_address) isn't simpler than canon_rtx (expanded_mem_address). * g++.dg/torture/pr40924.C: New test. Added: trunk/gcc/testsuite/g++.dg/torture/pr40924.C Modified: trunk/gcc/ChangeLog trunk/gcc/dse.c trunk/gcc/testsuite/ChangeLog -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40924
[Bug rtl-optimization/40924] [4.4 Regression] miscompiles with -03 (seemingly related to attribute may_alias)
--- Comment #7 from jakub at gcc dot gnu dot org 2009-08-05 12:54 --- Subject: Bug 40924 Author: jakub Date: Wed Aug 5 12:54:21 2009 New Revision: 150484 URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=150484 Log: PR rtl-optimization/40924 * dse.c (canon_address): Before calling cselib_expand_value_rtx make sure canon_rtx (mem_address) isn't simpler than canon_rtx (expanded_mem_address). * g++.dg/torture/pr40924.C: New test. Added: branches/gcc-4_4-branch/gcc/testsuite/g++.dg/torture/pr40924.C Modified: branches/gcc-4_4-branch/gcc/ChangeLog branches/gcc-4_4-branch/gcc/dse.c branches/gcc-4_4-branch/gcc/testsuite/ChangeLog -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40924
[Bug rtl-optimization/40924] [4.4 Regression] miscompiles with -03 (seemingly related to attribute may_alias)
--- Comment #8 from jakub at gcc dot gnu dot org 2009-08-05 12:55 --- Fixed. -- jakub at gcc dot gnu dot org changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution||FIXED http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40924
[Bug rtl-optimization/40924] [4.4 Regression] miscompiles with -03 (seemingly related to attribute may_alias)
--- Comment #4 from jakub at gcc dot gnu dot org 2009-08-04 10:27 ---
On the 4.4 branch/x86_64-linux, I can reproduce even with -O1 on:
extern C void abort (void);
#define _MAY_ALIAS __attribute__((__may_alias__))
typedef struct { float v[2]; } _float_v;
typedef struct { int v[2]; } _int_v;
typedef unsigned int _UInt _MAY_ALIAS;
typedef signed int _Int _MAY_ALIAS;
typedef float _Float _MAY_ALIAS;
static inline unsigned short less_than (_int_v a, _int_v b)
{
unsigned short r = 0;
const _UInt *p1 = (const _UInt *) a;
const _UInt *p2 = (const _UInt *) b;
for (int i=0; i 2; i++)
if (p1[i] p2[i]) r |= (1 i);
return r;
}
static inline _int_v multiply (_int_v b, _int_v c)
{
_int_v r;
_Int *p3 = (_Int *) c;
for (int i=0; i 2; i++)
r.v[i] = (int) (b.v[i] * p3[i] 0x);
return r;
}
static inline _float_v gather (_int_v indexes, const void *baseAddr)
{
_float_v r;
_Int *idx = (_Int *) indexes;
_Float *src = (_Float *) baseAddr;
for (int i=0; i 2; i++)
r.v[i] = *(src + idx[i]);
return r;
}
static inline _int_v add (const _int_v b, const _int_v c)
{
_int_v result;
_Int *r = (_Int *) result;
for (int i=0; i 2; i++)
r[i] = b.v[i] + c.v[i];
return result;
}
struct uint_v
{
_int_v data;
inline uint_v () { data.v[0] = 0; data.v[1] = 1; }
inline uint_v (unsigned int a) {
for (int i=0; i 2; i++)
*(_UInt *) data.v[i] = a;
}
inline uint_v (_int_v x) : data (x) {}
inline uint_v operator* (const uint_v x) const { return multiply (data,
x.data); }
inline uint_v operator+ (const uint_v x) const { return uint_v (add (data,
x.data)); }
inline unsigned short operator (const uint_v x) const { return less_than
(data, x.data); }
};
struct float_v
{
_float_v data;
explicit inline float_v (const uint_v x) {
_UInt *p2 = (_UInt *) x.data;
for (int i=0; i 2; i++)
data.v[i] = p2[i];
}
inline float_v (const float *array, const uint_v indexes) {
const uint_v offsets = indexes * uint_v (1);
data = gather (offsets.data, array);
}
__attribute__((noinline)) unsigned short operator== (const float_v x) const
{
unsigned short r = 0;
for (int i=0; i 2; i++)
if (data.v[i] == x.data.v[i]) r |= (1 i);
return r;
}
};
int main ()
{
const float array[2] = { 2, 3 };
unsigned short mask;
for (uint_v i; (mask = (i 2)) == 3; i = i + 2) {
const float_v ii (i + 2);
asm volatile (# Barrier 1 %0 %1 %2 : : r (ii), r (i), r (array) :
memory);
float_v a (array, i);
asm volatile (# Barrier 2 %0 %1 %2 %3 : : r (ii), r (i), r
(array), r (a) : memory);
if ((a == ii) != 3)
abort();
}
return 0;
}
Apparently there is some stack slot sharing and RTL DSE decides to remove a
store to stack related address as dead when that memory is later on read using
a non-%rsp related read.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40924
[Bug rtl-optimization/40924] [4.4 Regression] miscompiles with -03 (seemingly related to attribute may_alias)
--- Comment #5 from jakub at gcc dot gnu dot org 2009-08-04 20:56 --- Patch posted: http://gcc.gnu.org/ml/gcc-patches/2009-08/msg00226.html -- jakub at gcc dot gnu dot org changed: What|Removed |Added AssignedTo|unassigned at gcc dot gnu |jakub at gcc dot gnu dot org |dot org | URL||http://gcc.gnu.org/ml/gcc- ||patches/2009- ||08/msg00226.html Status|NEW |ASSIGNED Last reconfirmed|2009-07-31 11:14:45 |2009-08-04 20:56:23 date|| http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40924
[Bug rtl-optimization/40924] [4.4 Regression] miscompiles with -03 (seemingly related to attribute may_alias)
--- Comment #2 from rguenth at gcc dot gnu dot org 2009-07-31 11:14 --- Confirmed. Trunk works for me. If I disable gcse the testcase is no longer miscompiled (likewise if I disable tree PRE which only hoists some conversions - thus likely const/copy propagation goes wrong or addresses are improperly rewritten). The RTL after expansion looks sane wrt alias sets. -- rguenth at gcc dot gnu dot org changed: What|Removed |Added Status|UNCONFIRMED |NEW Component|middle-end |rtl-optimization Ever Confirmed|0 |1 Keywords||alias, wrong-code Known to fail||4.4.1 Known to work||4.4.0 4.5.0 Last reconfirmed|-00-00 00:00:00 |2009-07-31 11:14:45 date|| Summary|4.4.1 regression: |[4.4 Regression] miscompiles |miscompiles with -03|with -03 (seemingly related |(seemingly related to |to attribute may_alias) |attribute may_alias)| Target Milestone|--- |4.4.2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40924
[Bug rtl-optimization/40924] [4.4 Regression] miscompiles with -03 (seemingly related to attribute may_alias)
--- Comment #3 from jakub at gcc dot gnu dot org 2009-07-31 12:13 --- This has been broken even on the trunk, since r146669 till r146847 (so it works again with r146848), no idea whether it is the same thing or not, nor whether r146848 really fixed it rather than just made it latent (and similarly whether r146669 broke it or just made it real rather than latent). -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40924
