http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47858
Summary: [4.5/4.6 Regression] IPA-SRA decreases quality of
debug info
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: ja...@gcc.gnu.org
CC: aol...@gcc.gnu.org
struct inode
{
char i_pad[16];
unsigned int i_flags;
};
struct dentry
{
unsigned int d_pad[16];
struct inode *d_inode;
};
extern int inode_permission (struct inode *, int);
extern int fsnotify_create (struct inode *, struct dentry *);
static inline int
may_create (struct inode *dir, struct dentry *child)
{
if (child->d_inode)
return -17;
if (((dir)->i_flags & 16))
return -2;
return inode_permission (dir, 2 | 1);
}
int
foo (struct inode *dir, struct dentry *child)
{
if (may_create (dir, child) < 0)
return -1;
return fsnotify_create (dir, child);
}
int
bar (struct inode *dir, struct dentry *child)
{
if (may_create (dir, child) < 0)
return -1;
return fsnotify_create (dir, child);
}
int
baz (struct inode *dir, struct dentry *child)
{
if (may_create (dir, child) < 0)
return -1;
return fsnotify_create (dir, child);
}
at -Os on x86_64-linux (distilled from Linux kernel) pessimizes debug info
because child parameter in may_create (which isn't emitted inline) doesn't have
location (well, it doesn't have even DW_TAG_formal_parameter in the out of line
DIE, just in the abstract inline DIE).
This could be solvable with my proposed DW_TAG_GNU_call_site stuff and the
(still in drafting DW_OP_GNU_parameter_ref stuff for completely optimized away
parameters - here it isn't completely optimized away, just replaced by
something based on it).
In this testcase it is of course also questionable why IPA-SRC actually
performs this "optimization" when it increases code size and doesn't improve
anything at all.
