[Bug c/24020] New: Excessive (x20) stack usage for 4.0 with -O3

[guillaume dot melquiond at ens-lyon dot fr]

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