* [Bug translator/20377] New: stable functions converted to @const aren't optimized
@ 2016-07-16 0:49 jistone at redhat dot com
2016-11-11 16:50 ` [Bug translator/20377] " mcermak at redhat dot com
0 siblings, 1 reply; 2+ messages in thread
From: jistone at redhat dot com @ 2016-07-16 0:49 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=20377
Bug ID: 20377
Summary: stable functions converted to @const aren't optimized
Product: systemtap
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: translator
Assignee: systemtap at sourceware dot org
Reporter: jistone at redhat dot com
Target Milestone: ---
Although @const does specify /* stable */ underneath, that doesn't let the
function containing it be treated as stable. We have quite a few tapset
functions that were converted from full embedded-c to this @const form, and
those have thus regressed in getting stable treatment.
Consider tid():
$ stap -e 'probe oneshot { println(tid(), tid()) }' -v -p2 \
| sed -ne '/^begin/,$p'
begin /* <- oneshot += begin <- oneshot */
{
println(__global_tid__overload_0(), __global_tid__overload_0());
__global_exit__overload_0();
}
Compare to ns_tid(), which didn't get converted to @const:
$ stap -e 'probe oneshot { println(ns_tid(), ns_tid()) }' -v -p2 \
| sed -ne '/^begin/,$p'
begin /* <- oneshot += begin <- oneshot */
# locals
__stable___global_ns_tid__overload_0_value:long
{
(__stable___global_ns_tid__overload_0_value) = (__global_ns_tid__overload_0());
println(__stable___global_ns_tid__overload_0_value,
__stable___global_ns_tid__overload_0_value);
__global_exit__overload_0();
}
We could treat this as a simple regression, and convert these functions back to
full embedded-c functions where /* stable */ works.
We could also treat this as an enhancement request to infer stable functions
from their contents. This is surely a hard problem, but we don't have to be
perfect as long as there are no false positives. A function that's nothing but
'return @const("foo")' should be an easy case.
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* [Bug translator/20377] stable functions converted to @const aren't optimized
2016-07-16 0:49 [Bug translator/20377] New: stable functions converted to @const aren't optimized jistone at redhat dot com
@ 2016-11-11 16:50 ` mcermak at redhat dot com
0 siblings, 0 replies; 2+ messages in thread
From: mcermak at redhat dot com @ 2016-11-11 16:50 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=20377
Martin Cermak <mcermak at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mcermak at redhat dot com
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