Post-Register Allocation Instruction Scheduling for Compiler Optimization

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Solution Overview

Problem

Existing compilers face performance limitations due to the inefficiencies in instruction scheduling and register allocation, leading to increased compilation time and memory overhead, as well as conflicts between the two processes, which restrict effective instruction scheduling.

Innovation Solution

A method for selective instruction scheduling is introduced, where post-register allocation scheduling is performed only on code regions that exceed a modification threshold and are marked as 'hot' or 'warm' based on execution frequency, allowing for optimized instruction reordering without unnecessary rescheduling of cold regions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If instruction scheduling is performed before register allocation, then instruction execution efficiency is improved, but register motion increases causing spills and pipeline stalls

Engineering Contradiction:
Improveinstruction execution efficiencyVSAvoidregister motion
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The patent inverts the conventional order by performing register allocation before instruction scheduling. This reversal allows the register allocator to establish a baseline allocation that instruction scheduling must work within, preventing excessive register motion and spills while still achieving execution efficiency through selective rescheduling of modified regions.

Inventive Principle:
Principle #13The other way round (Inversion)

Solution Approach 2:

The patent applies partial instruction scheduling by focusing only on modified regions of code that exceed a threshold. Rather than rescheduling entire basic blocks, the system selectively schedules only the portions of code that were modified by register allocation, reducing compilation overhead while maintaining performance benefits in critical areas.

Inventive Principle:
Principle #16Partial or excessive action

2Reliability

If register allocation precedes instruction scheduling, then register conflicts are minimized, but false constraints limit instruction movement and organization

Engineering Contradiction:
Improveregister allocation accuracyVSAvoidinstruction scheduling effectiveness
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent applies partial instruction scheduling by focusing only on modified regions of code that exceed a threshold. Rather than rescheduling entire basic blocks, the system selectively schedules only the portions of code that were modified by register allocation, reducing compilation overhead while maintaining performance benefits in critical areas.

Inventive Principle:
Principle #16Partial or excessive action

Solution Approach 2:

The patent changes the parameter of instruction scheduling from a comprehensive approach to a selective approach based on modification thresholds. By monitoring whether regions exceed a certain threshold of modifications, the system dynamically adjusts the scheduling effort applied to different code regions, optimizing the balance between allocation accuracy and scheduling effectiveness.

Inventive Principle:
Principle #35Parameter changes

3Loss of time

If simple instruction scheduling is applied, then compilation time is reduced, but performance gains in compiled code are limited

Engineering Contradiction:
Improvecompilation timeVSAvoidcompiled code performance
Core Design Contradiction:
Loss of timeVSProductivity

Solution Approach 1:

The patent applies local quality by differentiating between modified and unmodified regions of code. Modified regions, which contain instructions affected by register allocation, receive full instruction scheduling treatment to maximize performance gains, while unmodified regions skip scheduling to minimize compilation time overhead.

Inventive Principle:
Principle #3Local quality

4Productivity

If complex instruction scheduling models are used, then compiled code performance is improved, but compilation time and memory overhead increase significantly

Engineering Contradiction:
Improvecompiled code performanceVSAvoidcompilation time
Core Design Contradiction:
ProductivityVSLoss of time

Solution Approach 1:

The patent applies partial instruction scheduling by focusing only on modified regions of code that exceed a threshold. Rather than rescheduling entire basic blocks, the system selectively schedules only the portions of code that were modified by register allocation, reducing compilation overhead while maintaining performance benefits in critical areas.

Inventive Principle:
Principle #16Partial or excessive action

Data Source

PatentUS7770161B2Post-register allocation profile directed instruction scheduling
Publication Date: 2010.08.03 X CORP
  • US7770161B2 patent drawing
  • US7770161B2 patent drawing
  • US7770161B2 patent drawing

AI summary

A computer implemented method, system, and computer usable program code for selective instruction scheduling. A determination is made whether a region of code exceeds a modification threshold after performing register allocation on the region of code. The region of code is marked as a modified region of code in response to the determination that the region of code exceeds the modification threshold. A determination is made whether the region of code exceeds an execution threshold in response to the determination that the region of code is marked as a modified region of code. Post-register allocation instruction scheduling is performed on the region of code in response to the determination that the region of code is marked as a modified region of code and the determination that the region of code exceeds the execution threshold.