When compiling the attached program (-std=c99 -march=i486 -O?), GCC allocates
the following stacks for the recursive function "f" (in bytes):
GCC 3.4.5 (20050821) -O2: 16 -O3: 16
GCC 4.0.2 (20050917) -O2: 40 -O3: 360 (!)
GCC 4.1.0 (20050904) -O2: 28 -O3: 28
There are only 10 local int variables in the function, so the 360-byte
consumption with GCC 4.0.2 seems a bit high, with respect to the 16 bytes with
GCC 3.4.5. Especially since the code actually runs 25% slower when compiled with
4.0.2 whatever the optimization level (17% with 4.1.0).
--
Summary: Excessive (x20) stack usage for 4.0 with -O3
Product: gcc
Version: 4.0.2
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: guillaume dot melquiond at ens-lyon dot fr
CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: i486-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24020
