Floating Point Control Override for Processor Latency Reduction
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Solution Overview
Problem
Modifying default rounding settings in processors for floating-point operations can cause latency and increased power consumption, as current methods require saving and restoring processor state, which is inefficient for performance-critical operations.
Innovation Solution
Implementing a method to override floating-point control settings on a per-instruction basis using override control data, allowing for bypassing access or modification of the floating-point control register, thereby improving efficiency by executing instructions with custom rounding modes and exception handling without altering the default settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the default rounding setting is modified by read and store operations in the floating-point control register, then the rounding setting can be changed to meet various conditions, but this causes latency and increased power consumption
Solution Approach 1:
The patent segments the rounding control mechanism into two parts: a global default rounding setting stored in the floating-point control register, and per-instruction rounding overrides encoded directly in instruction operands. This allows most instructions to use the default setting without modification, while specific instructions can override it locally, eliminating the need for global state changes and reducing latency.
Solution Approach 2:
The patent applies local quality by allowing rounding mode to be specified at the instruction level rather than globally. Each floating-point instruction can carry its own rounding mode specification in its operands, enabling precise local control of rounding behavior without affecting other instructions. This local control eliminates the need to read and write the control register for each rounding change.
2Adaptability or versatility
If the default rounding setting is modified by read and store operations in the floating-point control register, then the rounding setting can be changed to meet various conditions, but this causes increased power consumption
Solution Approach 1:
The patent segments the rounding control mechanism into a global default setting and per-instruction overrides, allowing most instructions to execute using the default setting without accessing the control register. Only the encoding of override values in instruction operands consumes power, not the actual read-modify-write cycle of the control register, thereby reducing overall power consumption.
Solution Approach 2:
The patent extracts the rounding mode specification from the control register and embeds it directly into the instruction operands. This extraction eliminates the need for control register access for per-instruction rounding changes, removing the associated power consumption from read and write operations while preserving the ability to change rounding settings.
3Reliability
If the current state data of the processor is saved and restored around modification of the default rounding setting, then the rounding setting can be safely changed, but this causes additional latency
Solution Approach 1:
The patent segments rounding control into global defaults and local overrides, so that per-instruction rounding changes do not require modifying the global control register state. Since the control register is not being modified, there is no need to save and restore processor state, eliminating the associated latency while maintaining reliability through the instruction-encoded override values.
Solution Approach 2:
The patent extracts the rounding mode from the control register and embeds it in the instruction itself. This extraction means that rounding settings become instruction-specific rather than state-dependent, eliminating the need for save/restore operations around rounding mode changes and the latency they introduce, while preserving correctness through explicit per-instruction control.
4Reliability
If the current state data of the processor is saved and restored around modification of the default rounding setting, then the rounding setting can be safely changed, but this causes additional power consumption
Solution Approach 1:
The patent segments rounding control into global defaults and local overrides, eliminating the need to modify the control register for per-instruction changes. Without control register modifications, there is no need for save/restore operations, thereby eliminating the power consumption associated with those operations while maintaining reliability through instruction-encoded overrides.
Solution Approach 2:
The patent extracts rounding mode specification from the control register state and embeds it directly in instruction operands. This extraction transforms rounding control from a state-modifying operation to a data-passing operation, eliminating the need for save/restore sequences and their associated power consumption while preserving correctness through explicit per-instruction rounding specifications.
Data Source
AI summary
Methods and apparatus relating to instructions with floating point control override are described. In an embodiment, a processor includes a first logic to receive an instruction having one or more bits corresponding to override control data. The override control data is to indicate one or more floating point operation settings that are to override one or more default settings. The processor also has a second logic to perform a floating point operation in response to the instruction and at least one of the one or more floating point operation settings.