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<html><head><title>VM Spec </title></head><body BGCOLOR=#eeeeff text=#000000 LINK=#0000ff VLINK=#000077 ALINK=#ff0000> <a href="VMSpecTOC.doc.html">Contents</a> | <a href="Instructions2.doc124.html">Prev</a> | <a href="Instructions2.doc126.html">Next</a> | <a href="Mnemonics.doc.html">Index</a><hr><br> <a name="jsr_w"></a><h2>jsr_w</h2><a name="jsr_w.Operation"></a><b>Operation</b><br><a name="69186"></a>Jump subroutine (wide index)<p><Table Border="3"><tr><td><a name="69177"></a> <i>jsr_w</i><td><a name="87568"></a> <tr><td><a name="69179"></a> <i>branchbyte1</i><td><a name="87568"></a> <tr><td><a name="69181"></a> <i>branchbyte2</i><td><a name="87568"></a> <tr><td><a name="69183"></a> <i>branchbyte3</i><td><a name="87568"></a> <tr><td><a name="69185"></a> <i>branchbyte4</i><td><a name="87568"></a> </Table><Table><tr><td></Table><p><a name="jsr_w.Forms"></a><b>Forms</b><br><a name="69187"></a><i>jsr_w</i> = 201 (0xc9)<p><a name="jsr_w.Stack"></a><b>Stack</b><br><a name="69188"></a>... <img src="chars/arrwdbrt.gif"> ..., <i>address</i><p><a name="jsr_w.Description"></a><b>Description</b><br><a name="69189"></a>The <i>address</i> of the opcode of the instruction immediately following this <i>jsr_w</i> instruction is pushed onto the operand stack as a value of type <code>returnAddress</code>. The unsigned <i>branchbyte1</i>, <i>branchbyte2</i>, <i>branchbyte3</i>, and <i>branchbyte4</i> are used to construct a signed 32-bit offset, where the offset is (<i>branchbyte1</i> << 24) | (<i>branchbyte2</i> << 16) | (<i>branchbyte3</i> << 8) | <i>branchbyte4</i>. Execution proceeds at that offset from the address of this <i>jsr_w</i> instruction. The target address must be that of an opcode of an instruction within the method that contains this <i>jsr_w </i>instruction.<p><a name="jsr_w.Notes"></a><b>Notes</b><br><a name="69190"></a>The <i>jsr_w</i> instruction is used with the <i>ret</i> instruction in the implementation of the <code>finally</code> clauses of the Java language (see <a href="Compiling.doc.html#13789">Section 7.13, "Compiling finally"</a>). Note that <i>jsr_w</i> pushes the address onto the stack and <i>ret</i> gets it out of a local variable. This asymmetry is intentional.<p><a name="69194"></a>Although the <i>jsr_w</i> instruction has a 4-byte branch offset, other factors limit the size of a Java method to 65535 bytes <a href="ClassFile.doc.html#6253">(§4.10)</a>. This limit may be raised in a future release of the Java Virtual Machine.<p><hr><!-- This inserts footnotes--><p><a href="VMSpecTOC.doc.html">Contents</a> | <a href="Instructions2.doc124.html">Prev</a> | <a href="Instructions2.doc126.html">Next</a> | <a href="Mnemonics.doc.html">Index</a><p><font size=-1>Java Virtual Machine Specification (HTML generated by dkramer on February 25, 1997)<br><i><a href="Copyright.doc.html">Copyright © 1996 Sun Microsystems, Inc.</a>All rights reserved</i><br>Please send any comments or corrections to <a href="mailto:doug.kramer@sun.com">doug.kramer@sun.com</a></font></body></html>⌨️ 快捷键说明
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