I'm having problems getting double-precision floating-point to work in
m5 for the MIPS isa.
The 32-bit MIPS isa has 32 32-bit floating-point registers.
Double-precision floating-point numbers are stored in pairs of
floating-point registers. At least that's how I understand it.
Simple floating point math used to work in m5 until changeset
781969fbeca9. After the change, it seams that m5 does not read two
32-bit floating point registers to get a double-precision
floating-point operand, but only one 32-bit floating-point register
(when it's simulating an add_d instruction, for example). This
results in incorrect floating point arithmetic.
I have the following C program (compiled for MIPS) that exercises the problem:
#include<stdio.h>
int main (void)
{
double x, y, z;
x = 5.0;
y = 0.1;
z = x + y;
printf ("z = %lf\n", z);
return 0;
}
It should print "z = 5.1", but it doesn't because the simulation of
the floating-point addition is wrong.
Can anyone tell me why this change was made that seems to break the
simulation of double-precision floating-point arithmetic in m5?
Thanks.
--
Cheers,
Matt
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