[Bug middle-end/52066] New: IRA and reginfo initialization too expensive
jakub at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Tue Jan 31 13:21:00 GMT 2012
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52066
Bug #: 52066
Summary: IRA and reginfo initialization too expensive
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: jakub@gcc.gnu.org
On compilation of an empty file, we spend almost half of the runtime on
IRA and reginfo cost initialization.
Inlining reg_class_subset_p and reg_classes_intersect_p gives us at least tiny
part of compile time back, at the cost of some small code growth.
For --enable-checking=release x86_64-linux cc1:
~/timing --drop 20 -c 2500 ./cc1.vanilla empty.c -quiet
Strip out best and worst 500 realtime results
minimum: 0.006243475 sec real / 0.000018634 sec CPU
maximum: 0.032220578 sec real / 0.000203440 sec CPU
average: 0.006542800 sec real / 0.000036352 sec CPU
stdev : 0.000050402 sec real / 0.000004406 sec CPU
~/timing --drop 20 -c 2500 ./cc1 empty.c -quiet
Strip out best and worst 500 realtime results
minimum: 0.006115241 sec real / 0.000017569 sec CPU
maximum: 0.033226603 sec real / 0.000197238 sec CPU
average: 0.006384943 sec real / 0.000036349 sec CPU
stdev : 0.000049180 sec real / 0.000004284 sec CPU
readelf -WS cc1{.vanilla,} | grep '\text'
[12] .text PROGBITS 00000000004b21a0 0b21a0 78e7b4 00 AX
0 0 16
[12] .text PROGBITS 00000000004b21a0 0b21a0 78ed34 00 AX
0 0 16
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