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Volume 4: Base IA-32 Instruction Reference
4:121
FDIV/FDIVP/FIDIV—Divide
Description
Divides the destination operand by the source operand and stores the result in the
destination location. The destination operand (dividend) is always in an FPU register;
the source operand (divisor) can be a register or a memory location. Source operands
in memory can be in single-real, double-real, word-integer, or short-integer formats.
The no-operand version of the instruction divides the contents of the ST(1) register by
the contents of the ST(0) register. The one-operand version divides the contents of the
ST(0) register by the contents of a memory location (either a real or an integer value).
The two-operand version, divides the contents of the ST(0) register by the contents of
the ST(
i
) register or vice versa.
The FDIVP instructions perform the additional operation of popping the FPU register
stack after storing the result. To pop the register stack, the processor marks the ST(0)
register as empty and increments the stack pointer (TOP) by 1. The no-operand version
of the floating-point divide instructions always results in the register stack being
popped. In some assemblers, the mnemonic for this instruction is FDIV rather than
FDIVP.
The FIDIV instructions convert an integer source operand to extended-real format
before performing the division. When the source operand is an integer 0, it is treated as
a +0.
If an unmasked divide by zero exception (#Z) is generated, no result is stored; if the
exception is masked, an
of the appropriate sign is stored in the destination operand.
The following table shows the results obtained when dividing various classes of
numbers, assuming that neither overflow nor underflow occurs.
Opcode
Instruction
Description
D8 /6
FDIV
m32real
Divide ST(0) by
m32real
and store result in ST(0)
DC /6
FDIV
m64real
Divide ST(0) by
m64real
and store result in ST(0)
D8 F0+i
FDIV ST(0), ST(
i
)
Divide ST(0) by ST(
i
) and store result in ST(0)
DC F8+i
FDIV ST(i), ST(0)
Divide ST(
i
) by ST(0) and store result in ST(
i
)
DE F8+i
FDIVP ST(
i
), ST(0)
Divide ST(
i
) by ST(0), store result in ST(
i
), and pop the register
stack
DE F9
FDIVP
Divide ST(1) by ST(0), store result in ST(1), and pop the
register stack
DA /6
FIDIV
m32int
Divide ST(0) by
m32int
and store result in ST(0)
DE /6
FIDIV
m16int
Divide ST(0) by
m64int
and store result in ST(0)
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 ...
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