dstore : store double in local variable : index : visitVarInsn()

Description

dstore pops a two-word double-precision float off the operand stack and stores it in a local variable. It takes a single parameter, <varnum>, an unsigned integer indicating which local variable to use.

Since double-precision floats are 64-bits wide, and each local variable can only hold up to 32 bits, Java uses two consecutive local variables, <varnum> and <varnum> + 1 to store a double. So dstore <varnum> actually modifies the values of both <varnum> (which is set to double-word1) and <varnum> + 1 (which is set to double-word2).

Both <varnum> and <varnum> + 1 must be valid local variable numbers in the current frame.

Example

ldc2_w 10.0      ; push the double 10.0 onto the stack
dstore 3        ; pop 10.0 off of the stack and store it in local variables 3 and 4

See also

lstore fstore istore astore wide

Stack

Before	After
doube-word1	...
double-word2	...
...	...

Bytecode

Type	Description
u1	dstore opcode = 0x39 (57)
u1	<varnum>

There is also a wide format for this instruction, which supports access to all local variables from 0 to 65535:

Type	Description
u1	wide opcode = 0xC4 (196)
u1	dstore opcode = 0x39 (57)
u2	<varnum>