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Volume 4: Base IA-32 Instruction Reference
4:243
JMP—Jump
Description
Transfers program control to a different point in the instruction stream without
recording return information. The destination (target) operand specifies the address of
the instruction being jumped to. This operand can be an immediate value, a
general-purpose register, or a memory location.
• Near jump – A jump to an instruction within the current code segment (the
segment currently pointed to by the CS register), sometimes referred to as an
intrasegment call.
• Far jump – A jump to an instruction located in a different segment than the current
code segment, sometimes referred to as an intersegment call.
• Task switch – A jump to an instruction located in a different task. (This is a form of
a far jump.)
Results in an IA-32_Intercept(Gate) in Itanium System
Environment.
A task switch can only be executed in protected mode (see Chapter 6 in the
Intel
Architecture Software Developer’s Manual, Volume 3
for information on task switching
with the JMP instruction).
When executing a near jump, the processor jumps to the address (within the current
code segment) that is specified with the target operand. The target operand specifies
either an absolute address (that is an offset from the base of the code segment) or a
relative offset (a signed offset relative to the current value of the instruction pointer in
the EIP register). An absolute address is specified directly in a register or indirectly in a
memory location (
r/m16
or
r/m32
operand form). A relative offset (
rel8
,
rel16
, or
rel32
) is generally specified as a label in assembly code, but at the machine code level,
it is encoded as a signed, 8-bit or 32-bit immediate value, which is added to the value
in the EIP register (that is, to the instruction following the JMP instruction). The
operand-size attribute determines the size of the target operand (16 or 32 bits) for
absolute addresses. Absolute addresses are loaded directly into the EIP register. When
a relative offset is specified, it is added to the value of the EIP register. If the
operand-size attribute is 16, the upper two bytes of the EIP register are cleared to 0s,
resulting in a maximum instruction pointer size of 16 bits. The CS register is not
changed on near jumps.
Opcode
Instruction
Description
EB
cb
JMP
rel8
Jump near, relative address
E9
cw
JMP
rel16
Jump near, relative address
E9
cd
JMP
rel32
Jump near, relative address
FF /4
JMP
r/m16
Jump near, indirect address
FF /4
JMP
r/m32
Jump near, indirect address
EA
cd
JMP
ptr16:16
Jump far, absolute address
EA
cp
JMP
ptr16:32
Jump far, absolute address
FF /5
JMP
m16:16
Jump far, indirect address
FF
/5
JMP
m16:32
Jump far, indirect address
Summary of Contents for ITANIUM ARCHITECTURE
Page 1: ......
Page 7: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 199: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Page 352: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Page 589: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Page 590: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Page 591: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 603: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...
Page 604: ......