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Analyzing SPARC assembly code is more conveniently done by following
some preliminary, formal steps, before figuring out which
algorithms are implemented by the code that is to be analyzed.
These formal steps are explained in introductory comments and
side-comments, while analyzing one code sample.
| Phase #1:
Replace opcodes through synthetic instructions |
A very first step is to replace operation codes with
synthetic instructions,
where applicable.
Code that contains synthetic instructions is easier to read.
In the same step, groups of pseudo ops can be replaced with complex ones
(complex ones being e.g. .indent).
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.section ".rodata1",#alloc
.align 4
.l0:
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.ascii "%u %u\n\000"
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identify replaceable pseudo-ops;
asciz
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.section ".text",#alloc,#execinstr
.align 4
.global main
main:
save %sp,-96,%sp
sethi %hi(.l0),%g2
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or %g0,1,%i1
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replace operation codes with
synthetic instructions;
mov
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or %g0,0,%o1
add %g2,%lo(.l0),%i0
or %g0,1,%o0
or %g0,0,%i2
.l1:
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subcc %i1,1,%g0
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cmp
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be .l7
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andcc %o0,1,%g0
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btst
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.l2:
bne .l3
srl %o0,1,%g2
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add %i2,1,%i2
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inc
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srl %o0,1,%o0
ba .l4
subcc %o0,1,%g0
.l3:
add %o0,%g2,%g2
add %i2,2,%i2
add %g2,1,%o2
subcc %o2,%o0,%g0
bcs .l6
or %g0,%o2,%o0
subcc %o0,1,%g0
.l4:
bne .l2
andcc %o0,1,%g0
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.l5:
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cut unused local labels
(labels could be replaced with
anonymous labels)
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ba .l8
subcc %i2,%o1,%g0
.l6:
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jmpl %i7+8,%g0
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ret
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restore %g0,0,%o0
.l7:
subcc %i2,%o1,%g0
.l8:
bleu,a .l9
add %i1,1,%i1
or %g0,%i0,%o0
or %g0,%i1,%o1
add %i1,1,%i1
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call printf
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call is already an opcode
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or %g0,%i2,%o2
or %g0,%i2,%o1
.l9:
or %g0,%i1,%o0
ba .l1
or %g0,0,%i2
.type main,2
.size main,(.-main)
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