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Appears in the Proceedings of the 39 th Annual IEEE/ACM International Symposium on Microarchitecture Dataflow Predication
| Content Provider | CiteSeerX |
|---|---|
| Author | Smith, Aaron Nagarajan, Ramadass Sankaralingam, Karthikeyan Mcdonald, Robert Burger, Doug Keckler, Stephen W. Mckinley, Kathryn S. |
| Abstract | Predication facilitates high-bandwidth fetch and large static scheduling regions, but has typically been too complex to implement comprehensively in out-of-order microarchitectures. This paper describes dataflow predication, which provides per-instruction predication in a dataflow ISA, low predication computation overheads similar to VLIW ISAs, and low complexity out-of-order issue. A twobit field in each instruction specifies whether an instruction is predicated, in which case, an arriving predicate token determines whether an instruction should execute. Dataflow predication incorporates three features that reduce predication overheads. First, dataflow predicate computation permits computation of compound predicates with virtually no overhead instructions. Second, early mispredication termination squashes in-flight instructions with false predicates at any time, eliminating the overhead of falsely predicated paths. Finally, implicit predication mitigates the fanout overhead of dataflow predicates by reducing the number of explicitly predicated instructions, by predicating only the heads of dependence chains. Dataflow predication also exposes new compiler optimizations–such as disjoint instruction merging and path-sensitive predicate removal–for increased performance of predicated code in an out-of-order design. 1. |
| File Format | |
| Access Restriction | Open |
| Subject Keyword | Dataflow Predication Microarchitecture Dataflow Predication Out-of-order Microarchitectures Predicated Code Low Predication Computation Per-instruction Predication Early Mispredication Termination High-bandwidth Fetch Low Complexity Out-of-order Issue Twobit Field Compound Predicate Out-of-order Design Dependence Chain Predication Overhead Dataflow Predicate Computation False Predicate Large Static Scheduling Region Dataflow Predicate Increased Performance New Compiler Optimization Vliw Isas Overhead Instruction In-flight Instruction Fanout Overhead Path-sensitive Predicate Removal Dataflow Isa Disjoint Instruction Merging Implicit Predication |
| Content Type | Text |
| Resource Type | Article |
