[Bug tree-optimization/15473] New: [tree-ssa] Sibcall optimization for libcalls.
kazu at cs dot umass dot edu
gcc-bugzilla@gcc.gnu.org
Mon May 17 00:47:00 GMT 2004
Consider:
long long
foo (long long a, long long b)
{
return a / b;
}
I get:
foo (a, b)
{
<bb 0>:
return a_1 / b_2;
}
with the assembly code being
foo:
subl $12, %esp
pushl 28(%esp)
pushl 28(%esp)
pushl 28(%esp)
pushl 28(%esp)
call __divdi3
addl $28, %esp
ret
Note that the sequence of 4 pushl instructions simply copy 16 bytes
from one location of the stack to another.
If I create a (non-libcall) function with the same arguments like so
long long div64 (long long a, long long b);
long long
bar (long long a, long long b)
{
return div64 (a, b);
}
I get:
bar (a, b)
{
long long int T.0;
<bb 0>:
T.0_3 = div64 (a_1, b_2) [tail call];
return T.0_3;
}
with the assembly code being
bar:
jmp div64
--
Summary: [tree-ssa] Sibcall optimization for libcalls.
Product: gcc
Version: 3.5.0
Status: UNCONFIRMED
Keywords: pessimizes-code
Severity: enhancement
Priority: P2
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: kazu at cs dot umass dot edu
CC: gcc-bugs at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15473
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