dcmp<op>

dcmp<op>

Forms
dcmpg = 152 (0x98) dcmpl = 151 (0x97)

Stack
..., value1.word1, value1.word2, value2.word1, value2.word1 ..., result

Description
Both value1 and value2 must be of type double. The values are popped from the operand stack, and a floating-point comparison is performed. If value1 is greater than value2, the int value 1 is pushed onto the operand stack. If value1 is equal to value2, the int value 0 is pushed onto the operand stack. If value1 is less than value2, the int value -1 is pushed onto the operand stack. If either value1 or value2 is NaN, the dcmpg instruction pushes the int value 1 onto the operand stack and the dcmpl instruction pushes the int value -1 onto the operand stack.

Floating-point comparison is performed in accordance with IEEE 754. All values other than NaN are ordered, with negative infinity less than all finite values and positive infinity greater than all finite values. Positive zero and negative zero are considered equal.

Notes
The dcmpg and dcmpl instructions differ only in their treatment of a comparison involving NaN. NaN is unordered, so any double comparison fails if either or both of its operands are NaN. With both dcmpg and dcmpl available, any double comparison may be compiled to push the same result onto the operand stack whether the comparison fails on non-NaN values or fails because it encountered a NaN. For more information, see Section 7.5, "More Control Examples."

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Java Virtual Machine Specification (HTML generated by dkramer on February 25, 1997)
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