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Branch prediction attempts to guess whether a conditional jump will be taken or not. Branch target prediction attempts to guess the target of a taken conditional or unconditional jump before it is computed by decoding and executing the instruction itself. Branch prediction and branch target prediction are often combined into the same circuitry.
An example of a simple hardware branch prediction scheme is to assume that all backward branches (i.e. to a smaller program counter) are taken (because they are part of a loop), and all forward branches (to a larger program counter) are not taken (because they leave a loop).
In computer architecture, predication is a feature that provides an alternative to conditional transfer of control, as implemented by conditional branch machine instructions. Predication works by having conditional ( predicated ) non-branch instructions associated with a predicate , a Boolean value used by the instruction to control whether the ...
Superscalar, branch prediction PowerPC e500: Dual 7 stage Multi-core PowerPC e600: 3-issue 7 stage Superscalar out-of-order execution, branch prediction PowerPC e5500: 2010 4-issue 7 stage Out-of-order, multi-core PowerPC e6500: 2012 Multi-core PowerPC 603: 4 5 execution units, branch prediction, no SMP PowerPC 603q: 1996 5 In-order PowerPC 604 ...
Example: A situation in which multiple instructions are ready to enter the execute instruction phase and there is a single ALU (Arithmetic Logic Unit). One solution to such resource hazard is to increase available resources, such as having multiple ports into main memory and multiple ALU (Arithmetic Logic Unit) units.
In computer architecture, a branch target predictor is the part of a processor that predicts the target, i.e., the address of the instruction that is executed next, of a taken conditional branch or unconditional branch instruction before the target of the branch instruction is computed by the execution unit of the processor.
The architecture implements predication, speculation, and branch prediction. It uses variable-sized register windowing for parameter passing. The same mechanism is also used to permit parallel execution of loops. Speculation, prediction, predication, and renaming are under control of the compiler: each instruction word includes extra bits for this.
The first example of the SUB followed by AND and the second example of LD followed by AND can be solved by stalling the first stage by three cycles until write-back is achieved, and the data in the register file is correct, causing the correct register value to be fetched by the AND's Decode stage. This causes quite a performance hit, as the ...