Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1399

F2XM1—Compute 2
Opcode
D9 F0
Description
Calculates the exponential value of 2 to the power of the source operand minus 1. The
source operand is located in register ST(0) and the result is also stored in ST(0). The
value of the source operand must lie in the range -1.0 to +1.0. If the source value is
outside this range, the result is undefined.
The following table shows the results obtained when computing the exponential value
of various classes of numbers, assuming that neither overflow nor underflow occurs:
ST(0) SRC
-1.0 to  0
 0
 0
+0 to +1.0
Values other than 2 can be exponentiated using the following formula:
 log
y (y
x = 2
Operation
ST(0)  (2
FPU Flags Affected
C1
C0, C2, C3
Additional Itanium System Environment Exceptions
Itanium Reg Faults Disabled FP Register Fault if PSR.dfl is 1, NaT Register Consumption
Floating-point Exceptions
#IS
#IA
#D
#U
#P
Volume 4: Base IA-32 Instruction Reference
x
-1
Instruction
F2XM1
ST(0) DEST
 0.5 to  0
 0
+0
+0 to 1.0
x)
2
ST(0)  1);
Set to 0 if stack underflow occurred.
Indicates rounding direction if the inexact-result exception (#P) is
generated: 0 = not roundup; 1 = roundup.
Undefined.
Abort.
Stack underflow occurred.
Source operand is an SNaN value or unsupported format.
Result is a denormal value.
Result is too small for destination format.
Value cannot be represented exactly in destination format.
Description
ST(0)
Replace ST(0) with (2 - 1)
4:97