A compare instruction tests for a single specified condition and generates a boolean result. These results are written to predicate registers. 4.3.1 predication Predication is the conditional execution of instructions. The execution of most IA-64 instructions is gated by a qualifying predicate.
Predicates are one-bit values and are stored in the predicate register file.
A few IA-64 instructions cannot be predicated. The setting of the two target registers is described below in Compare Types . Compare instructions are summarized in Table 4-8 . The compare instructions set two predicate targets according to the result. The fcmp instruction compares two floating-point registers and sets two predicate targets according to one of eight relations.