Examples
Predicated instructions were popular in European computer designs of the 1950s, including the Mailüfterl (1955), the Zuse Z22 (1955), the ZEBRA (1958), and the Electrologica X1 (1958). The IBM ACS-1 design of 1967 allocated a "skip" bit in its instruction formats, and the CDC Flexible Processor in 1976 allocated three conditional execution bits in its microinstruction formats.
In Intel's IA-64 architecture, almost every instruction in the IA-64 instruction set is predicated. The predicates themselves are stored in special purpose registers; one of the predicate registers is always true so that unpredicated instructions are simply instructions predicated with the value true. The use of predication is essential in the IA-64 implementation of software pipelining because it avoids the need for writing separated code for prologs and epilogs.
On the ARM architecture, almost all instructions can be conditionally executed. Thirteen different predicates are available, each depending on the four flags Carry, Overflow, Zero, and Negative in some way. The ARM's 16-bit Thumb instruction set has no branch predication, in order to save encoding space, but its successor Thumb-2 overcomes this problem using a special instruction which has no effect other than to supply predicates for the next four instructions.
For a concrete example of code exploiting branch predication, see the ARM assembly example in binary GCD algorithm.
Read more about this topic: Branch Predication
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