Skip direct-dominating live-in optimization for loop headers

[guosran]

Summary

This pr addresses issue #270.

Problem

In nested loop kernels, values defined in outer loop blocks and used in inner loop bodies were incorrectly classified as "direct dominating live-ins" by CanonicalizeLiveInPass. This prevented them from being promoted to block arguments, which in turn caused TransformCtrlToDataFlowPass to not create inner-rate PHI_START operations for them.

Fix

Before applying the direct-dominating optimization, check whether the using block is a loop header. If so, skip the optimization and let the value be promoted to a block argument.

Result

After the fix, the GEP pointer is correctly promoted to a block argument in ^bb4:

^bb1:
  %6 = neura.gep(%arg0, shl(i, 4))
  neura.br ..., %6 : !llvm.ptr, ... to ^bb4

^bb4(%15: i64, %16: i32, %17: !llvm.ptr, ...):  // %17 is now a block arg
  gep(%17, %15)

And TransformCtrlToDataFlowPass creates an inner-rate PHI_START for it:

%9  = neura.gep(%arg0, shl(i, 4))          // outer-rate GEP
%17 = neura.phi_start %9, %16              // inner-rate PHI_START for the pointer
%22 = neura.gep(%17, %21)                  // inner-loop body uses inner-rate pointer

TODO

Have not updated all failed checks yet, will do so once the changes are reviewed and approved. gemv has been updated.

[guosran]

Commits from the previous unmerged pr is shown here. This pr should start from 1f60123 (the first failed commit).

[Copilot]

Pull request overview

This PR fixes an SSA live-in canonicalization bug impacting nested loops by preventing the “direct-dominating live-in” optimization from firing on loop headers, enabling correct promotion to block arguments and subsequent inner-rate PHI_START creation during ctrl-to-data-flow lowering. It also renames/rewires mapping and task placement passes and updates affected tests/docs accordingly.

Changes:

• Update CanonicalizeLiveInPass to skip the direct-dominating-live-in optimization for loop headers (fix for #270).
• Rename MapToAcceleratorPass → MapOperationOnTilePass and update pass registration, build files, docs, and tests.
• Replace MapTaskOnCgraPass with AllocateCgraToTaskPass and invoke global placement from ResourceAwareTaskOptimizationPass, updating taskflow tests.

Reviewed changes

Copilot reviewed 43 out of 46 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
test/neura/steer_ctrl/loop_with_return_value.mlir	Updates disabled mapping pass invocation name in test pipeline comments.
test/neura/fusion/test.mlir	Updates mapping pass name and adjusts FileCheck IDs after mapping changes.
test/neura/for_loop/relu_test.mlir	Updates mapping pass flag name in RUN line.
test/neura/ctrl/branch_for.mlir	Updates mapping pass flag name in RUN lines.
test/multi-cgra/taskflow/resource-heavy/resource-heavy.mlir	Splits long RESOPT attribute checks for readability/stability.
test/multi-cgra/taskflow/resnet/simple_resnet_tosa.mlir	Splits long RESOPT attribute checks for readability/stability.
test/multi-cgra/taskflow/parallel-nested/parallel-nested.mlir	Switches to --allocate-cgra-to-task and updates RESOPT/placement checks.
test/multi-cgra/taskflow/multi-nested/multi-nested.mlir	Switches to --allocate-cgra-to-task and updates placement + RESOPT expectations.
test/multi-cgra/taskflow/irregular-loop/irregular-loop.mlir	Switches to --allocate-cgra-to-task and splits RESOPT checks.
test/multi-cgra/kernel_mapping/relu/relu.mlir	Updates mapping pass flag name in RUN line.
test/multi-cgra/kernel_mapping/loop-in-kernel/loop-in-kernel.mlir	Updates mapping pass flag name in RUN line.
test/multi-cgra/kernel_mapping/fir/fir.mlir	Updates mapping pass flag name in RUN line.
test/mapping_quality/tiny_loop.mlir	Updates mapping pass flag name in RUN lines.
test/mapping_quality/branch_for.mlir	Updates mapping pass flag name in RUN lines.
test/honor_arch/fir_removed_tiles_test.mlir	Updates mapping pass flag name in RUN line.
test/e2e/relu/relu_kernel.mlir	Updates mapping pass flag name in RUN line.
test/e2e/histogram/histogram_kernel.mlir	Updates mapping pass flag name in RUN line.
test/e2e/gemv/gemv_kernel.mlir	Updates mapping pass flag name and refreshes extensive mapping/YAML/ASM FileCheck expectations.
test/e2e/fir/fir_kernel_vec.mlir	Updates mapping pass flag name in RUN line.
test/e2e/fir/fir_kernel.mlir	Updates mapping pass flag name in RUN line.
test/e2e/axpy/axpy_kernel.mlir	Updates mapping pass flag name in RUN line.
test/controflow_fuse/simple_loop_reduction/simple_loop_reduction.mlir	Updates mapping pass flag name in RUN line.
test/controflow_fuse/simple_loop/simple_loop.mlir	Updates mapping pass flag name in RUN line.
test/controflow_fuse/perfect_nested/perfect_nested.mlir	Updates mapping pass flag name in RUN line.
test/code_gen/test_code_generate.mlir	Updates mapping pass flag name in RUN line.
test/c2llvm2mlir/simple_loop/test.mlir	Updates mapping pass flag name in RUN line.
test/c2llvm2mlir/nested_loop/test.mlir	Updates mapping pass flag name in RUN line.
test/arch_spec/README.md	Updates documentation to use --map-operation-on-tile.
lib/TaskflowDialect/Transforms/Optimizations/ResourceAwareTaskOptimizationPass.cpp	Renames mapper references and invokes AllocateCgraToTask-based placement at convergence.
lib/TaskflowDialect/Transforms/CMakeLists.txt	Swaps in AllocateCgraToTaskPass.cpp and adds Optimizations subdirectory.
lib/TaskflowDialect/Transforms/AllocateCgraToTaskPass.cpp	Implements new task+SRAM placement pass with multi-CGRA placement search.
lib/TaskflowDialect/CMakeLists.txt	Adjusts subdirectory structure so Optimizations is included via Transforms.
lib/NeuraDialect/Transforms/MapOperationOnTilePass.cpp	Renames mapper pass (class/argument/logs) and updates factory function.
lib/NeuraDialect/Transforms/CanonicalizeLiveInPass.cpp	Skips direct-dominating-live-in optimization when the using block is a loop header.
lib/NeuraDialect/Transforms/CMakeLists.txt	Replaces MapToAcceleratorPass.cpp with MapOperationOnTilePass.cpp.
lib/NeuraDialect/NeuraPasses.cpp	Updates conversion pipeline to run createMapOperationOnTilePass().
include/TaskflowDialect/TaskflowPasses.td	Renames pass definition to allocate-cgra-to-task.
include/TaskflowDialect/TaskflowPasses.h	Updates pass factory name and adds runAllocateCgraToTask() helper declaration.
include/NeuraDialect/NeuraPasses.td	Renames pass definition to map-operation-on-tile and updates constructor name.
include/NeuraDialect/NeuraPasses.h	Renames pass factory API to createMapOperationOnTilePass.
include/NeuraDialect/Architecture/Architecture.h	Updates reference in comment to new mapper pass name.

Comments suppressed due to low confidence (4)

lib/TaskflowDialect/Transforms/AllocateCgraToTaskPass.cpp:285

• placement.primary() returns {-1,-1} when placement.cgra_positions is empty, but the code still pushes it into task_node->placement. That can result in invalid task_mapping_info (row/col = -1) and can skew the SRAM centroid computation in later iterations. Handle the no-placement case explicitly (e.g., signal pass failure / emit an error, or keep the task unannotated and skip SRAM assignment) before committing any placement.
  lib/TaskflowDialect/Transforms/AllocateCgraToTaskPass.cpp:281
• When a placement can’t be found for cgra_count, the pass falls back to cgra_count-1 but does not update the task’s cgra_count (or tile_shape) attribute accordingly. That can leave IR in an inconsistent state where cgra_count disagrees with the number of entries in task_mapping_info.cgra_positions, which downstream passes may rely on. Consider either failing the pass, or updating the attributes to match the chosen fallback placement (and possibly iterating fallback down to 1).
  lib/TaskflowDialect/Transforms/AllocateCgraToTaskPass.cpp:432
• parseTileShapeOffsets() is introduced but never used, and the placement search currently ignores each task’s tile_shape attribute (even though other code paths/comments imply placement should respect it). If tile_shape is intended to constrain the physical shape, wire this helper into findBestPlacement() (read the task’s tile_shape StringAttr, validate it matches cgra_count, then call tryPlaceShape() with those offsets). Otherwise, remove the dead helper / update comments to reflect that the allocator chooses shapes autonomously.
  lib/TaskflowDialect/Transforms/AllocateCgraToTaskPass.cpp:553
• The non-rectangular shape search uses a 64-bit bitmask (1ULL << (nr * grid_cols_ + nc)). If grid_rows * grid_cols >= 64, this shift becomes undefined and the mask cannot represent all cells. Add a guard/assert limiting the supported grid size (e.g., 4x4) or switch to a wider/dynamic bitset representation for visited states.

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