User Guide

264 x87 Floating-Point Programming
AMD64 Technology 24592—Rev. 3.15—November 2009
The FILD instruction converts the 16-bit, 32-bit, or 64-bit source signed integer in memory into a
double-extended-precision floating-point value and pushes the result onto the top-of-stack, ST(0).
The FIST instruction converts and rounds the source value in the top-of-stack, ST(0), to a signed
integer and copies it to the specified 16-bit or 32-bit memory location. The type of rounding is
determined by the rounding control (RC) field of the x87 control word.
The FISTP instruction is similar to FIST, except that FISTP can also store the result to a 64-bit
memory location and it pops ST(0) after the store.
The FISTTP instruction converts a floating-point value in ST(0) to an integer by truncating the
fractional part of the number and storing the integer result to the memory address specified by the
destination operand. FISTTP then pops the floating point register stack. The FISTTP instruction
ignores the rounding mode specified by the x87 control word.
Convert and Load or Store BCD
• FBLD—Floating-Point Load Binary-Coded Decimal
• FBSTP—Floating-Point Store Binary-Coded Decimal Integer and Pop
The FBLD and FBSTP instructions, respectively, push and pop an 80-bit packed BCD memory value
on and off the top-of-stack, ST(0). FBLD first converts the value being p ushed to a double-extended-
precision floating-point value. FBSTP rounds the value being popped to an integer, using the rounding
mode specified by the RC field, and converts the value to an 80-bit packed BCD value. Thus, no
FRNDIT (round-to-integer) instruction is needed prior to FBSTP.
Conditional Move
• FCMOVB—Floating-Point Conditional Move If Below
• FCMOVBE—Floating-Point Conditional Move If Below or Equal
• FCMOVE—Floating-Point Conditional Move If Equal
• FCMOVNB—Floating-Point Conditional Move If Not Below
• FCMOVNBE—Floating-Point Conditional Move If Not Below or Equal
• FCMOVNE—Floating-Point Conditional Move If Not Equal
• FCMOVNU—Floating-Point Conditional Move If Not Unordered
• FCMOVU—Floating-Point Conditional Move If Unordered
The FCMOVcc instructions copy the contents of a specified stack position, ST(i), to the top-of-stack,
ST(0), if the specified rFLAGS condition is met. Table 6-13 on page 265 specifies the flag
combinations for each conditional move.