<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html> <head> <title>cmp<kind></title> <link rel=stylesheet href="opcode.css"> </head> <body> <h1>cmp<kind></h1> <h2>Purpose</h2> <p> Perform the indicated floating point or long comparison, storing 0 if the two arguments are equal, 1 if the second argument is larger, or -1 if the first argument is larger. The "bias" listed for the floating point operations indicates how NaN comparisons are treated: "Gt bias" instructions return 1 for NaN comparisons, and "lt bias" instructions return -1. </p> <p> For example, to check to see if floating point a < b, then it is advisable to use cmpg-float; a result of -1 indicates that the test was true, and the other values indicate it was false either due to a valid comparison or because one or the other values was NaN. </p> <h2>Details</h2> <table class="instruc"> <thead> <tr> <th>Op & Format</th> <th>Mnemonic / Syntax</th> <th>Arguments</th> </tr> </thead> <tbody> <tr> <td>2d..31 23x</td> <td>cmp<i>kind</i> vAA, vBB, vCC<br/> 2d: cmpl-float <i>(lt bias)</i><br/> 2e: cmpg-float <i>(gt bias)</i><br/> 2f: cmpl-double <i>(lt bias)</i><br/> 30: cmpg-double <i>(gt bias)</i><br/> 31: cmp-long </td> <td><code>A:</code> destination register (8 bits)<br/> <code>B:</code> first source register or pair<br/> <code>C:</code> second source register or pair</td> </tr> </tbody> </table> <h2>Constraints</h2> <ul> <li> A, B and C must be valid register indices in the current stack frame. </li> <li> For the two -float variants, both vB and vC must be of type float. </li> <li> For the two -double variants, both vB and vC must be the lower part of a register pair holding a double value. </li> <li> For the -long variant, both both vB and vC must be the lower part of a register pair holding a long value. </li> </ul> <h2>Behavior</h2> <ul> <li> The values of registers vB and vC are compared. The result, which is stored in vA, is one of the following three: <ul> <li> If vB < vC, then vA'=-1. </li> <li> If vB == vC, then vA'=0. </li> <li> If vC > vC, then vA'=1. </li> </ul> </li> <li> For the -float and -double variants, an addition "bias" specifies what happens if one or both of the arguments are NaN: <ul> <li> A "lt bias" results in vA'=-1. </li> <li> A "gt bias" results in vA'=1. </li> </ul> </li> <li> If v(A-1) is the lower half of a register pair, v(A-1)' becomes undefined. </li> <li> If v(A+1) is the upper half of a register pair, v(A+1)' becomes undefined. </li> </ul> <h2>Exceptions</h2> <p> None. </p> </body> </html>