[OpenMP Dialect] Add omp.canonical_loop operation. by shraiysh · Pull Request #65380 · llvm/llvm-project (original) (raw)

Conversation

This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.Learn more about bidirectional Unicode characters

[ Show hidden characters]({{ revealButtonHref }})

This patch continues the work of D147658. It adds the omp.canonical_loop operation as the basic block for everything loop-related in OpenMP, such as worksharing-loop, distribute, loop transformation, etc.

In contrast to the current omp.wsloop approach

• Loop-related semantics need to be implemented only once
• Is composable with OpenMP loop transformations such as unrolling, tiling.
• Is supposed to eventually support non-rectangular loops
• Supports expressing non-perfectly nested loops

This patch only adds the MLIR representation; to something useful, I still have to implement lowering from Flang with at least the DO construct, and lowering to LLVM-IR using the OpenMPIRBuilder.

The pretty syntax currently is

omp.canonical_loop $iv in [0, %tripcount) { ... }

where [0, %tripcount) represents the half-open integer range of an OpenMP logical iteration space. Unbalanced parentheses/brackets and 0 keyword might not be universally liked. I could think of alternatives such as

omp.canonical_loop $iv = range(%tripcount) { ... }

Differential Revision: https://reviews.llvm.org/D155765