ganenkokb-yandex#1

Introduction

Here we introduce AOT generation support for ia32.
The lack of AOT support for ia32 is primarily due to the fact that the x64 approach with the allocation of 2 CODE_REG and PP_REG registers did not scale to the ia32 architecture due to the fact that there were so few free registers that the implementation of many instructions and stubs became impossible or time-consuming. A different approach and custom implementation for ia32 were required. In the dart-sdk project such work was stopped at some point due to the fact that ia32 was no longer supported at the OS developer level. Nevertheless, there was a request for ia32 support in the community and we decided to try to implement it.

What this prototype is about

For AOT on ia32 we use the following approach:

• x64 AOT implementation of flowgraph compiler, instructions and stubs was used as is for ia32
• assembler work with objects was moved to a pool of objects, as is done in all platforms that support AOT. We take the code completely from the x64 implementation also
• implementations that are very different on ia32 and x64, such as write barrier, are also used with x64 implementations
• transfer the operation of registers to memory for: CODE_RED, PP_REG, ABI enums registers, which began to be used in ia32 from the x64 implementation
• turn off intrinsify, because the assembly code requires significant edits, which is not the purpose of this prototype.

Stability issues

To verify the correctness of the dart sdk, we used tests on the x64 and ia32 platforms.
To do this, we completely transferred the work of x64 to memory instead of registers, and thus we had the opportunity to run tests on x64 and compare them with tests on ia32. The corresponding changes in the x64 code and tests are presented in the prototype. The changes in the x64 functionality serve as a demonstration of the approach and are not a demonstration of the final code.

Summary

Introduced prototype was integrated with flutter engine build and provided AOT work on ia32, still having support of JIT.