Resource Table For If-Then-Else Code; Determining The Minimum Iteration Interval - Texas Instruments TMS320C6000 Programmer's Manual

6.8.4

Determining the Minimum Iteration Interval

Table 6–18. Resource Table for If-Then-Else Code
(a) A side
Unit(s) Instructions
.M1
.S1 SHL & B
.D1 LDH
.L1, .S1, or .D1 ADD & SUB
Total non-.M units
With nine instructions, the minimum iteration interval is at least 2, because a
maximum of eight instructions can be in parallel. Based on the way the depen-
dency graph in Figure 6–17 is split, five instructions are on the A side and four
are on the B side. Because none of the instructions are MPYs, all instructions
must go on the .S, .D, or .L units, which means you have a total of six
resources.
LDH must be on a .D unit.
SHL, B, and MVK must be on a .S unit.
The ADDs and SUB can be on the .S, .L, or .D units.
The AND can be on a .S or .L unit, or .D unit ('C64x only)
From Table 6–18, you can see that no one resource is used more than two
times, so the minimum iteration interval is still 2.
Total/Unit
0
2
1
2
5
The minimum iteration interval is also affected by the total number of instruc-
tions. Because three units can perform nonmultiply operations on a given side,
a total of five instructions can be performed with a minimum iteration interval
of 2. Because only four instructions are on the B side, the minimum iteration
interval is still 2.
Optimizing Assembly Code via Linear Assembly
If-Then-Else Statements in a Loop
(b) B side
Unit(s) Instructions
.M2
.S2 MVK
.L2 CMPEQ
.L2 or .S2 AND
.L2, .S2, or .D2 ADD
Total non-.M units
Total/Unit
0
1
1
1
1
4
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