Add FP8/BF8 support for LDS transpose load#2210
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Add FP8/BF8 support for LDS transpose load#2210stefankoncarevic wants to merge 12 commits intodevelopfrom
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Pull request overview
Adds FP8/BF8 enablement for Rock’s LDS transpose-load path on gfx950, including support for scaled FP8 MFMA geometries that use ds_read_tr8_b64, and expands testing coverage accordingly.
Changes:
- Extend LDS transpose-load utility/lowering to handle FP8/BF8 element types, including quad-rate scaled FP8 geometries (16x128, 32x64).
- Update LDS transpose MFMA-geometry validation and
rock.lds_transpose_loadop verification for 8-bit types (vector length = 8). - Add new e2e + MLIR tests covering FP8/BF8 and mixed fp8/bf8 combinations.
Reviewed changes
Copilot reviewed 11 out of 11 changed files in this pull request and generated 6 comments.
Show a summary per file
| File | Description |
|---|---|
| mlir/lib/Dialect/Rock/utility/LdsTransposeLoad.cpp | Implements FP8/BF8 lane→offset mapping, quad-rate load sequencing, and type-compatibility updates. |
| mlir/lib/Dialect/Rock/IR/RockDialect.cpp | Extends rock.lds_transpose_load verifier to accept FP8/BF8 and enforce expected vector length. |
| mlir/include/mlir/Dialect/Rock/IR/RockOps.td | Broadens op type constraints to allow FP8/BF8 memrefs and non-fixed vector results (checked in verifier). |
| mlir/lib/Dialect/Rock/IR/RockDialect.cpp | Updates LDS transpose config geometry validation error message. |
| mlir/include/mlir/Dialect/Rock/utility/LdsTransposeLoad.h | Updates public header docs to reflect new types/geometries. |
| mlir/include/mlir/Dialect/Rock/IR/RockAttrDefs.td | Updates KDim documentation to include 64/128. |
| mlir/lib/Dialect/Rock/IR/RockDialect.cpp | Updates LDS transpose config verification to allow (16,128) and (32,64). |
| mlir/test/Dialect/Rock/ops.mlir | Adds FP8 rock.lds_transpose_load + new config-attr test cases. |
| mlir/test/Dialect/Rock/lowering_load_transpose_lds.mlir | Adds lowering checks for FP8 transpose-load legalization. |
| mlir/test/Dialect/Rock/lds_transpose_error.mlir | Updates expected error text for expanded valid geometry set. |
| mlir/test/e2e/PrLdsTransposeLoadFp8.toml | New e2e suite for FP8/BF8 LDS transpose-load (including mixed-type cases). |
| mlir/test/e2e/PrLdsTransposeLoadFp8.cfg | Gating for the new e2e suite based on lds_transpose_load feature. |
| mlir/test/e2e/CMakeLists.txt | Wires the new e2e suite into CMake. |
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Pull request overview
Adds gfx950 FP8/BF8 enablement for the LDS transpose-load optimization path (ds_read_tr8_b64), including support for scaled FP8 MFMA geometries and mixed fp8/bf8 GEMM type combinations, plus accompanying IR + e2e tests.
Changes:
- Extend LDS transpose load utility to support FP8/BF8 (vector length 8) and scaled FP8 MFMA geometries (16x128, 32x64) with quad-rate load sequencing.
- Update Rock dialect verification/constraints and tests to cover new supported geometries and element types.
- Add new FP8/BF8 e2e regression suite and hook it into the e2e CMake target list.
Reviewed changes
Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| mlir/lib/Dialect/Rock/utility/LdsTransposeLoad.cpp | Core implementation: FP8/BF8 support, new geometry handling, quad-rate offset/load logic |
| mlir/lib/Dialect/Rock/IR/RockDialect.cpp | Verifier updates: LDS transpose config geometry list; LDS transpose load result vector length checks |
| mlir/include/mlir/Dialect/Rock/IR/RockOps.td | Expand operand element types; loosen result type to be enforced by verifier |
| mlir/include/mlir/Dialect/Rock/utility/LdsTransposeLoad.h | Header/docs updated for new types and geometries |
| mlir/include/mlir/Dialect/Rock/IR/RockAttrDefs.td | Doc update: KDim now includes 64/128 |
| mlir/test/Dialect/Rock/ops.mlir | New IR tests covering fp8 lds_transpose_load and new config attrs |
| mlir/test/Dialect/Rock/lowering_load_transpose_lds.mlir | Lowering checks for fp8 transpose_load generation |
| mlir/test/Dialect/Rock/lds_transpose_error.mlir | Update expected error messages for expanded valid geometry list |
| mlir/test/e2e/PrLdsTransposeLoadFp8.toml | New e2e suite covering fp8/bf8 + mixed combos |
| mlir/test/e2e/PrLdsTransposeLoadFp8.cfg | Feature-gate for the new e2e suite |
| mlir/test/e2e/CMakeLists.txt | Register new e2e suite in the PR test list |
Comments suppressed due to low confidence (1)
mlir/lib/Dialect/Rock/utility/LdsTransposeLoad.cpp:170
isValidMfmaGeometry()now treats scaled FP8 geometries (16x128, 32x64) as generally valid, but the non-FP8 lane mapping path ingetBasePanelOffsets()does not handle these and will hitllvm_unreachableif they ever occur with f16/bf16 types. To avoid potential compiler crashes on inconsistent inputs, add an element-type-dependent geometry check inmakeDecision()(or before callinggetBasePanelOffsets) so 16x128/32x64 are only accepted when the element type is FP8/BF8.
// Validate MFMA geometry
if (!isValidMfmaGeometry(shape.mnMfma, shape.kMfma)) {
return dec;
}
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- Remove duplicate entries in getMfmaInsnInfoMap - Clarify neutral scale creation comment in AccelEmitter.cpp - Rename zeroAttr to neutralScaleAttr for clarity
Implement ds_read_tr8_b64 offset formulas for FP8/BF8 MFMA (16x32, 32x16). Enable mixed fp8/bf8 type combinations for GEMM operations on gfx950.
Disable LDS transpose for FP8 GEMM when K >= 1280 or small square matrices (K == N < 512) to avoid performance regressions while preserving compile time benefits.Add FP8 GEMM heuristic to selectively disable LDS transpose
- Add (32,64) geometry support in LdsTransposeLoad.cpp: - New getBasePanelOffsets() branch for 32x64 quad-rate formula - k_block = block_id / 2, m_block = block_id % 2 - kOffsetBase = k_local + k_block * 32 - mOffsetBase = m_parity * 8 + m_block * 16 - Update isQuadRate detection to include 32x64 - Add validation for (32,64) in RockDialect.cpp - Extend tuning ranges for scaled FP8 testing: - kPackPerBlock: added 64 - kPack: added 32 (for k_base=32) Co-authored-by: Cursor <cursoragent@cursor.com>
… check in LDSTransposeLoadOp::verify, update suite 4 test count comment
exact set of valid vector types and drop the now-redundant verifier checks. Add ldsTransposeConfig structural checks to ThreadwiseReadIntoOp::verify (rank-1 + static dest, supported element type, (geometry, type) consistency). Replace the assert + .value() in emitThreadwiseHWTranspose with emitOpError to avoid UB in release builds and reject non-rank-1 / dynamic destinations up-front. Use AmdArchInfo::hasLdsTransposeLoad for arch gating, share a single isValidLdsTransposeMfmaGeometry helper, align the numWaves formula with computeWaveGridLayout, drop the dead (tuning only emits power-of-2 wave-tile factors), and refresh doc comments. Add four negative ODS-coverage tests for the result-type constraint.
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Resolves:
Implement ds_read_tr8_b64 offset formulas for FP8/BF8 MFMA (16x32, 32x16, 16x128, 32x64). Enable mixed fp8/bf8 type combinations for GEMM operations on gfx950.
Motivation
Add FP8 and BF8 data type support for LDS transpose load optimization on gfx950.
This enables efficient matrix loads using
ds_read_tr8_b64hardware instructionTechnical Details
LdsTransposeLoad.cpp: Implemented FP8/BF8 offset formulas ingetBasePanelOffsets()LdsTransposeLoad.cpp: Updated type compatibility check inmakeDecision()areBothFp8Types()check to allow mixed fp8/bf8 combinationsTest Plan
Test Result