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UM0438

Simplified mnemonics for VLE instructions

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A.5.2

Simplified mnemonics that incorporate CR conditions (eliminates

BO32 and BO16 and replaces BI32 with crS)

The mnemonics in Table 24 are variations of the branch-if-condition-true (BO32 = 1 or BO16

= 1) and branch-if-condition-false (BO32 = 0 or BO16 = 0) encodings. Because these

instructions do not depend on the CTR, the true/false conditions specified by either BO32 or

BO16 can be combined with the CR test bit specified by the BI32 or BI16 operand to create

a different set of simplified mnemonics that eliminates the BO32 and BO16 operands and

the portion of the BI32 and BI16 operands (BI32[2–3] and BI16[0–1]) that specifies one of

the four possible test bits. However, for simplified mnemonics using the BO32 operand, the

simplified mnemonic cannot specify in which of the four CR fields (CR0–CR3) the test bit

falls, so the BI32 operand is replaced by a crS operand.

The standard codes shown in Table 22 are used for the most common combinations of

branch conditions. For ease of programming, these codes include synonyms; for example,

less than or equal (le) and not greater than (ng) achieve the same result.

Note:

A CR field symbol, cr0–cr3, is used as the first operand after the simplified mnemonic. If the

default, CR0, is used, no crS is necessary.

Decrement CTR, branch if CTR

≠ 0

e_bcl 2,0,target

e_bdnzl target(2)

Decrement CTR, branch if CTR = 0

e_bcl 3,0,target

e_bdzl target 2

Instructions for which B032 is either 1 (branch if condition true) or 0 (branch if condition false) do not depend on the CTR

value and can be alternately coded by incorporating the condition specified by the BI32 field. See Section A.5.2: Simplified

mnemonics that incorporate CR conditions (eliminates BO32 and BO16 and replaces BI32 with crS)

Simplified mnemonics for branch instructions that do not test CR bits should specify only a target. Otherwise, a

programming error may occur.

Table 21.

Simplified mnemonics for e_bcl with LR update (continued)

Branch semantics

e_bcl

Simplified

mnemonic

Table 22.

Standard coding for branch conditions

Code

Description

Equivalent

Bit Tested

Less than

—

Less than or equal (equivalent to ng)

Equal

—

Greater than or equal (equivalent to nl)

Greater than

—

Not less than (equivalent to ge)

Not equal

—

Not greater than (equivalent to le)

Summary overflow

—

Not summary overflow

—

Unordered (after floating-point comparison)

—

Not unordered (after floating-point comparison)

—

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