MIPS double precision immediates

Question

I'm trying to create an equivalent of li for double-precision numbers. It seems like the following should work, but it doesn't:

.main: 
    li $t0, 0
    li $t1, 5
    mtc1 $t1, $f12
    mtc1 $t0, $f13
    li $v0, 3
    syscall

When I look at $f12 and $f13 it has the value 5, which I think should be interpreted as 5*2^0. But it's not. Instead, it gives me 2.5E-323. What am I doing wrong? I think SPIM lets you do this, so I've been diving through their source unsuccessfully to copy it.

score 2 · Accepted Answer · answered Apr 24 '11 at 16:34

2

You have created a denormalized number (using an exponenent value of zero and a non-zero mantissa). You need to look at the format of doubles.

answered Apr 24 '11 at 16:34

Doug Currie

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MIPS double precision immediates

1 Answers1