is stored in register ST(1) and 0 with the sign of the source
operand is stored in register ST(0).
Opcode |
Instruction |
Description |
|---|---|---|
|
D9 F4 |
FXTRACT |
Separate value in ST(0) into exponent and significand, store exponent in ST(0), and push the significand onto the register stack. |
Separates the source value in the ST(0) register into its exponent and significand, stores the exponent in ST(0), and pushes the significand onto the register stack. Following this operation, the new top-of-stack register ST(0) contains the value of the original significand expressed as a real number. The sign and significand of this value are the same as those found in the source operand, and the exponent is 3FFFH (biased value for a true exponent of zero). The ST(1) register contains the value of the original operand's true (unbiased) exponent expressed as a real number. (The operation performed by this instruction is a superset of the IEEE-recommended logb(x) function.)
This instruction and the F2XM1 instruction are useful for performing power and range scaling operations. The FXTRACT instruction is also useful for converting numbers in extended-real format to decimal representations (e.g., for printing or displaying).
If the floating-point zero-divide exception (#Z) is masked and the source
operand is zero, an exponent value of - is stored in register ST(1) and 0 with the sign of the source
operand is stored in register ST(0).
TEMP 
Significand(ST(0));
ST(0) Exponent(ST(0));
TOP TOP - 1;
ST(0) TEMP;
C1 - Set to 0 if stack underflow occurred; set to 1 if stack overflow occurred.
C0, C2, C3 - Undefined.
#IS - Stack underflow occurred. Stack overflow occurred.
#IA - Source operand is an SNaN value or unsupported format.
#Z - ST(0) operand is ±0.
#D - Source operand is a denormal value.
#NM - EM or TS in CR0 is set.
#NM - EM or TS in CR0 is set.
#NM - EM or TS in CR0 is set.
For details, see Volume 2A and Volume 2B of the Intel(R) 64 and IA-32 Intel Architecture Software Developer's Manual. For the latest updates on the instruction set information, go to the web site.