When I compile this function:
double f(long double i) {return (i);}
with gcc flags -S -O3, I get the assembly below.
There are two redundant FPU instructions there. double value is already in FPU
after fldt. No need to store it and load it back since difference between
double and long double is only in memory representation, and in FPU registers
they are the same.
---- asm output (relevant part) ----
f:
pushl %ebp
movl %esp, %ebp
subl $8, %esp <---- redundant related stack adjustment
fldt 8(%ebp)
fstpl -8(%ebp) <---- redundant STORE
fldl -8(%ebp) <---- redundant LOAD
leave
ret
--
Summary: redundant instructions with long double returned value
Product: gcc
Version: 4.4.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: yuri at tsoft dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41462
