INSTRUCTION SET OVERVIEW
5-12
5.2.6
Comparison
The processor provides several types of instructions for comparing two operands, as described in
the following subsections.
5.2.6.1
Compare and Conditional Compare
These instructions compare two operands then set the condition code bits in the AC register
according to the results of the comparison:
These all use the REG format and can specify literals or local or global registers. The condition
code bits are set to indicate whether one operand is less than, equal to, or greater than the other
operand. See
section 3.7.2, “Arithmetic Controls (AC) Register” (pg. 3-18)
for a description of the
condition codes for conditional operations.
cmpi
and
cmpo
simply compare the two operands and set the condition code bits accordingly.
concmpi
and
concmpo
first check the status of condition code bit 2:
•
When not set, the operands are compared as with
cmpi
and
cmpo
.
•
When set, no comparison is performed and the condition code flags are not changed.
The conditional-compare instructions are provided specifically to optimize two-sided range
comparisons to check when A is between B and C (i.e., B
≤
A
≤
C). Here, a compare instruction
(
cmpi
or
cmpo
) checks one side of the range (e.g., A
≥
B) and a conditional compare instruction
(
concmpi
or
concmpo
) checks the other side (e.g., A
≤
C) according to the result of the first
comparison. The condition codes following the conditional comparison directly reflect the results
of both comparison operations. Therefore, only one conditional branch instruction is required to
act upon the range check; otherwise, two branches would be needed.
chkbit
checks a specified bit in a register and sets the condition code flags according to the bit
state. The condition code is set to 010
2
when the bit is set and 000
2
otherwise.
cmpi
Compare Integer
cmpib
Compare Integer Byte
cmpis
Compare Integer Short
cmpo
Compare Ordinal
concmpi
Conditional Compare Integer
concmpo
Conditional Compare Ordinal
chkbit
Check Bit
Содержание i960 Jx
Страница 1: ...Release Date December 1997 Order Number 272483 002 i960 Jx Microprocessor Developer s Manual ...
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Страница 25: ...1 INTRODUCTION ...
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Страница 35: ...2 DATA TYPES AND MEMORY ADDRESSING MODES ...
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Страница 47: ...3 PROGRAMMING ENVIRONMENT ...
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Страница 73: ...4 CACHE AND ON CHIP DATA RAM ...
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Страница 85: ...5 INSTRUCTION SET OVERVIEW ...
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Страница 111: ...6 INSTRUCTION SET REFERENCE ...
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Страница 195: ...INSTRUCTION SET REFERENCE 6 83 6 Opcode mov 5CCH REG movl 5DCH REG movt 5ECH REG movq 5FCH REG See Also LOAD STORE lda ...
Страница 233: ...7 PROCEDURE CALLS ...
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Страница 257: ...8 FAULTS ...
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Страница 291: ...9 TRACING AND DEBUGGING ...
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Страница 309: ...10 TIMERS ...
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Страница 325: ...11 INTERRUPTS ...
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Страница 369: ...12 INITIALIZATION AND SYSTEM REQUIREMENTS ...
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Страница 413: ...13 MEMORY CONFIGURATION ...
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Страница 429: ...14 EXTERNAL BUS ...
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Страница 469: ...15 TEST FEATURES ...
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Страница 493: ...A CONSIDERATIONS FOR WRITING PORTABLE CODE ...
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Страница 503: ...B OPCODES AND EXECUTION TIMES ...
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Страница 515: ...C MACHINE LEVEL INSTRUCTION FORMATS ...
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Страница 523: ...D REGISTER AND DATA STRUCTURES ...
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Страница 551: ...GLOSSARY ...
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Страница 561: ...INDEX ...
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