I use gcc-4.1.2 for MIPS64 configured as
/tmp/gcc-4.1.2/configure --target=mips64-none-elf --enable-threads=no
--disable-shared --enable-long-long --enable-c99 --enable-languages=c
--enable-multilib --enable-symvers=gnu --disable-libmudflap
--disable-libssp --disable-libgcc_eh --with-newlib --with-dwarf2
--with-system-zlib --enable-checking=release
--enable-generated-files-in-srcdir --verbose --prefix=/home/niva/local
--srcdir=/tmp/gcc-4.1.2 --enable-cpp
I compile the file poly.c:
double poly(double x)
{
double y = 1.0 + x * (2.0 + x * (3.0 + x * (4.0 + x)));
return y;
}
using the following command line:
mips64-none-elf-gcc-4.1.2 -O3 -fno-merge-constants -mips64 -Wall -W -S
-o ttt.s ttt.c -G0
(I cannot use -G8 because the operating environment does not allow use
of .sdata sections.)
The resulting assembler code looks like this:
.rdata
.align 3
$LC0:
.word 1074790400
.word 0
.align 3
$LC1:
.word 1074266112
.word 0
.align 3
$LC2:
.word 1073741824
.word 0
.align 3
$LC3:
.word 1072693248
.word 0
.text
.align 2
.align 3
.globl poly
.ent poly
poly:
.frame $sp,0,$31 # vars= 0, regs= 0/0, args= 0, gp= 0
.mask 0x00000000,0
.fmask 0x00000000,0
.set noreorder
.set nomacro
lui $2,%hi($LC0)
ldc1 $f0,%lo($LC0)($2)
lui $2,%hi($LC1)
ldc1 $f1,%lo($LC1)($2)
add.d $f0,$f12,$f0
lui $2,%hi($LC2)
madd.d $f0,$f1,$f12,$f0
ldc1 $f1,%lo($LC2)($2)
lui $2,%hi($LC3)
madd.d $f0,$f1,$f12,$f0
ldc1 $f1,%lo($LC3)($2)
j $31
madd.d $f0,$f1,$f12,$f0
Two commands are used to access each constant.
Q: Is it possible to make GCC use a common base register for
accessing all of the constants in a function?
