Block-Based Processor Nullification Instructions
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Solution Overview
Problem
Current processor architectures, particularly RISC designs, face limitations in performance improvement due to sustained complexity and overhead in hardware and software resources, with reduced benefits from transistor scaling and out-of-order superscalar implementations.
Innovation Solution
The implementation of block-based processor architectures (BB-ISAs) with explicit data graph execution (EDGE) that execute instructions as atomic blocks, reducing the need for complex architectural features like register renaming and misspeculation recovery, and using nullification instructions to manage predicated execution paths efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If out-of-order superscalar implementations are used to improve processor performance, then execution speed increases, but hardware complexity and resource overhead increase
Solution Approach 1:
The processor divides instructions into fixed-size blocks (e.g., 4 instructions per block) that are executed as atomic units. This segmentation simplifies the control logic by eliminating the need for complex out-of-order execution mechanisms while maintaining parallel execution capabilities through block-level operations.
Solution Approach 2:
The processor implements dynamic block execution where blocks can be speculatively executed and later committed or discarded based on predicate outcomes. This dynamic approach allows performance optimization through speculation while keeping the underlying hardware simpler compared to traditional out-of-order superscalar designs.
2Productivity
If register renaming and misspeculation recovery features are added to improve performance, then execution throughput increases, but area and energy consumption increase
Solution Approach 1:
The patent extracts and removes complex features like register renaming and misspeculation recovery from the processor architecture. By eliminating these resource-intensive features and replacing them with simpler block-based predicated execution, the processor achieves comparable performance with reduced area and energy consumption.
Solution Approach 2:
Instead of maintaining complex renaming tables and recovery mechanisms, the processor uses disposable block execution where speculative blocks are executed temporarily and discarded if predicates are not satisfied. This approach trades the complexity of long-lived renaming structures for short-lived, simple block operations.
3Productivity
If predicated execution paths are implemented to improve performance, then instruction-level parallelism increases, but the need for nullification instructions increases complexity
Solution Approach 1:
The patent merges the nullification operation with the predicated execution mechanism itself. By integrating nullification into the block commit logic, the processor handles multiple register writes atomically without requiring separate nullification instructions, thereby reducing instruction complexity while maintaining ILP.
Solution Approach 2:
The processor performs preliminary tracking of all register writes within a block during the execution phase. Before committing the block, it determines which writes should be nullified based on predicate outcomes, allowing efficient handling of predicated execution paths without adding complexity to the instruction stream.
Data Source
AI summary
Apparatus and methods are disclosed for nullifying one or more registers identified in a target field of a nullification instruction. In some examples of the disclosed technology, an apparatus can include memory and one or more block-based processor cores configured to fetch and execute a plurality of instruction blocks. One of the cores can include a control unit configured, based at least in part on receiving a nullification instruction, to obtain a register identification of at least one of a plurality of registers, based on a target field of the nullification instruction. A write to the at least one register associated with the register identification is nullified. The nullification instruction is in a first instruction block of the plurality of instruction blocks. Based on the nullified write to the at least one register, a subsequent instruction is executed from a second, different instruction block.