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* [Bug debug/54256] New: IPA-SRA debug info issues
@ 2012-08-14 15:00 jakub at gcc dot gnu.org
0 siblings, 0 replies; only message in thread
From: jakub at gcc dot gnu.org @ 2012-08-14 15:00 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54256
Bug #: 54256
Summary: IPA-SRA debug info issues
Classification: Unclassified
Product: gcc
Version: 4.7.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: jakub@gcc.gnu.org
CC: jamborm@gcc.gnu.org, jan.kratochvil@redhat.com
struct A
{
#ifdef PAD
void *c;
#endif
struct A *a;
void *b;
};
typedef int FN (struct A *);
extern void *v;
struct A *fn (void);
void
foo (FN *y, int z)
{
struct A *x = fn ();
baz (x, y, z);
}
static int
bar (FN *x, struct A *y, int z, int w)
{
if (v)
undef (8, v);
(*x) (y->a);
}
int
baz (struct A *x, FN *y, int z)
{
bar (y, x, z, 0);
return 0;
}
at -g -O2 doesn't provide debug info for the foo y parameter, eventhough it
actually is passed. The reason for that seems to be that IPA-SRA? decides to
not pass struct A *, but actually struct A ** instead (address of the a field
of a, i.e. essentially the exactly same pointer), we generate
DW_OP_GNU_parameter_ref but in the end at the call site the argument isn't
available (it is only available in the called function).
Not sure why IPA-SRA does this change (and with -DPAD it is actually a code
pessimization), supposedly because it hopes for scalarization opportunities in
the caller which at the end don't come though.
I've tried:
struct A { void *c; struct A *a; void *b; };
typedef int FN (struct A *);
extern void *v;
struct A *fn (void);
void
foo (FN *y, int z)
{
struct A x = { fn (), 0 };
baz (&x, y, z);
}
static int
bar (FN *x, struct A *y, int z, int w)
{
if (v)
undef (8, v);
(*x) (y->a);
}
int
baz (struct A *x, FN *y, int z)
{
bar (y, x, z, 0);
return 0;
}
but even that isn't scalarized in the caller, so I wonder when it is actually
useful this way.
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2012-08-14 15:00 [Bug debug/54256] New: IPA-SRA debug info issues jakub at gcc dot gnu.org
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