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Volume 4: Base IA-32 Instruction Reference
FADD/FADDP/FIADD—Add
Description
Adds the destination and source operands and stores the sum in the destination
location. The destination operand is always an FPU register; the source operand 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 adds the contents of the ST(0) register to the
ST(1) register. The one-operand version adds the contents of a memory location (either
a real or an integer value) to the contents of the ST(0) register. The two-operand
version, adds the contents of the ST(0) register to the ST(
i
) register or vice versa. The
value in ST(0) can be doubled by coding:
FADD ST(0), ST(0);
The FADDP 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 add instructions always results in the register stack being
popped. In some assemblers, the mnemonic for this instruction is FADD rather than
FADDP.)
The FIADD instructions convert an integer source operand to extended-real format
before performing the addition.
The table on the following page shows the results obtained when adding various classes
of numbers, assuming that neither overflow nor underflow occurs.
When the sum of two operands with opposite signs is 0, the result is +0, except for the
round toward
mode, in which case the result is
0. When the source operand is an
integer 0, it is treated as a +0.
When both operand are infinities of the same sign, the result is
of the expected sign.
If both operands are infinities of opposite signs, an invalid-operation exception is
generated.
Opcode
Instruction
Description
D8 /0
FADD
m32 real
Add
m32real
to ST(0) and store result in ST(0)
DC /0
FADD
m64real
Add
m64real
to ST(0) and store result in ST(0)
D8 C0+i
FADD ST(0), ST(i)
Add ST(0) to ST(i) and store result in ST(0)
DC C0+i
FADD ST(i), ST(0)
Add ST(i) to ST(0) and store result in ST(
i
)
DE C0+i
FADDP ST(i), ST(0)
Add ST(0) to ST(i), store result in ST(
i
), and pop the register
stack
DE C1
FADDP
Add ST(0) to ST(1), store result in ST(1), and pop the register
stack
DA /0
FIADD
m32int
Add
m32int
to ST(0) and store result in ST(0)
DE /0
FIADD
m16int
Add
m16int
to ST(0) 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 ...
Page 604: ......