[Mlir-commits] [mlir] [mlir][vector] Support multi-dimensional vectors in VectorFromElementsLowering (PR #151175)
Yang Bai
llvmlistbot at llvm.org
Tue Jul 29 08:48:47 PDT 2025
https://github.com/yangtetris created https://github.com/llvm/llvm-project/pull/151175
This patch extends the `VectorFromElementsLowering` conversion pattern to support
vectors of any rank, removing the previous restriction to 1D vectors only.
**Implementation Details:**
1. **0D vectors**: Handled explicitly since LLVMTypeConverter converts them to
length-1 1D vectors
2. **1D vectors**: Direct construction using llvm.insertelement operations
3. **N-D vectors**: Two-phase construction:
- Build 1D vectors for the innermost dimension using `llvm.insertelement`
- Assemble them into the nested aggregate structure using `llvm.insertvalue`
and `nDVectorIterate`
4. Use direct LLVM dialect operations instead of intermediate vector.insert operations for efficiency
**Example:**
```mlir
// Before: Failed for rank > 1
%v = vector.from_elements %e0, %e1, %e2, %e3 : vector<2x2xf32>
// After: Converts to nested aggregate
%poison = llvm.mlir.poison : !llvm.array<2 x vector<2xf32>>
%inner0 = llvm.insertelement %e0, %poison_1d[%c0] : vector<2xf32>
%inner0 = llvm.insertelement %e1, %inner0[%c1] : vector<2xf32>
%inner1 = llvm.insertelement %e2, %poison_1d[%c0] : vector<2xf32>
%inner1 = llvm.insertelement %e3, %inner1[%c1] : vector<2xf32>
%result = llvm.insertvalue %inner0, %poison[0] : !llvm.array<2 x vector<2xf32>>
%result = llvm.insertvalue %inner1, %result[1] : !llvm.array<2 x vector<2xf32>>
```
>From cf8174fcde57f8092409171ae19444886aca3625 Mon Sep 17 00:00:00 2001
From: yangtetris <baiyang0132 at gmail.com>
Date: Tue, 29 Jul 2025 23:41:22 +0800
Subject: [PATCH] [mlir] Support lowering multi-dim vectors in
VectorFromElementsLowering
---
.../VectorToLLVM/ConvertVectorToLLVM.cpp | 63 ++++++++++++++++---
.../vector-to-llvm-interface.mlir | 24 +++++++
2 files changed, 79 insertions(+), 8 deletions(-)
diff --git a/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp b/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp
index 17a79e3815b97..26d056cadb19c 100644
--- a/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp
+++ b/mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp
@@ -1890,15 +1890,62 @@ struct VectorFromElementsLowering
ConversionPatternRewriter &rewriter) const override {
Location loc = fromElementsOp.getLoc();
VectorType vectorType = fromElementsOp.getType();
- // TODO: Multi-dimensional vectors lower to !llvm.array<... x vector<>>.
- // Such ops should be handled in the same way as vector.insert.
- if (vectorType.getRank() > 1)
- return rewriter.notifyMatchFailure(fromElementsOp,
- "rank > 1 vectors are not supported");
Type llvmType = typeConverter->convertType(vectorType);
- Value result = LLVM::PoisonOp::create(rewriter, loc, llvmType);
- for (auto [idx, val] : llvm::enumerate(adaptor.getElements()))
- result = vector::InsertOp::create(rewriter, loc, val, result, idx);
+ Type llvmIndexType = typeConverter->convertType(rewriter.getIndexType());
+
+ Value result;
+ // 0D vectors are converted to legnth-1 1D vectors by LLVMTypeConverter.
+ if (vectorType.getRank() == 0) {
+ result = LLVM::PoisonOp::create(rewriter, loc, llvmType);
+ auto index0 = LLVM::ConstantOp::create(rewriter, loc, llvmIndexType, 0);
+ result = LLVM::InsertElementOp::create(rewriter, loc, result, adaptor.getElements().front(), index0);
+ rewriter.replaceOp(fromElementsOp, result);
+ return success();
+ }
+
+ // Build 1D vectors for the innermost dimension
+ int64_t innerDimSize = vectorType.getShape().back();
+ int64_t numInnerVectors = vectorType.getNumElements() / innerDimSize;
+
+ SmallVector<Value> innerVectors;
+ innerVectors.reserve(numInnerVectors);
+
+ auto innerVectorType = VectorType::get(innerDimSize, vectorType.getElementType());
+ Type llvmInnerType = typeConverter->convertType(innerVectorType);
+
+ int64_t elementInVectorIdx = 0;
+ Value innerVector;
+ for (auto val : adaptor.getElements()) {
+ if (elementInVectorIdx == 0)
+ innerVector = LLVM::PoisonOp::create(rewriter, loc, llvmInnerType);
+ auto position = LLVM::ConstantOp::create(rewriter, loc, llvmIndexType, elementInVectorIdx);
+ innerVector = LLVM::InsertElementOp::create(rewriter, loc, llvmInnerType, innerVector, val, position);
+ if (++elementInVectorIdx == innerDimSize) {
+ innerVectors.push_back(innerVector);
+ elementInVectorIdx = 0;
+ }
+ }
+
+ // For 1D vectors, we can just return the first innermost vector.
+ if (vectorType.getRank() == 1) {
+ rewriter.replaceOp(fromElementsOp, innerVectors.front());
+ return success();
+ }
+
+ // Now build the nested aggregate structure from these 1D vectors.
+ result = LLVM::PoisonOp::create(rewriter, loc, llvmType);
+
+ // Use the same iteration approach as VectorBroadcastScalarToNdLowering to
+ // insert the 1D vectors into the aggregate.
+ auto vectorTypeInfo = LLVM::detail::extractNDVectorTypeInfo(vectorType, *getTypeConverter());
+ if (!vectorTypeInfo.llvmNDVectorTy)
+ return failure();
+ int64_t vectorIdx = 0;
+ nDVectorIterate(vectorTypeInfo, rewriter, [&](ArrayRef<int64_t> position) {
+ result = LLVM::InsertValueOp::create(rewriter, loc, result,
+ innerVectors[vectorIdx++], position);
+ });
+
rewriter.replaceOp(fromElementsOp, result);
return success();
}
diff --git a/mlir/test/Conversion/VectorToLLVM/vector-to-llvm-interface.mlir b/mlir/test/Conversion/VectorToLLVM/vector-to-llvm-interface.mlir
index 31e17fb3e3cc6..834858c0b7c8f 100644
--- a/mlir/test/Conversion/VectorToLLVM/vector-to-llvm-interface.mlir
+++ b/mlir/test/Conversion/VectorToLLVM/vector-to-llvm-interface.mlir
@@ -2286,6 +2286,30 @@ func.func @from_elements_0d(%arg0: f32) -> vector<f32> {
// -----
+// CHECK-LABEL: func.func @from_elements_3d(
+// CHECK-SAME: %[[ARG_0:.*]]: f32, %[[ARG_1:.*]]: f32, %[[ARG_2:.*]]: f32, %[[ARG_3:.*]]: f32)
+// CHECK: %[[UNDEF_VEC0:.*]] = llvm.mlir.poison : vector<2xf32>
+// CHECK: %[[C0_0:.*]] = llvm.mlir.constant(0 : i64) : i64
+// CHECK: %[[VEC0_0:.*]] = llvm.insertelement %[[ARG_0]], %[[UNDEF_VEC0]][%[[C0_0]] : i64] : vector<2xf32>
+// CHECK: %[[C1_0:.*]] = llvm.mlir.constant(1 : i64) : i64
+// CHECK: %[[VEC0_1:.*]] = llvm.insertelement %[[ARG_1]], %[[VEC0_0]][%[[C1_0]] : i64] : vector<2xf32>
+// CHECK: %[[UNDEF_VEC1:.*]] = llvm.mlir.poison : vector<2xf32>
+// CHECK: %[[C0_1:.*]] = llvm.mlir.constant(0 : i64) : i64
+// CHECK: %[[VEC1_0:.*]] = llvm.insertelement %[[ARG_2]], %[[UNDEF_VEC1]][%[[C0_1]] : i64] : vector<2xf32>
+// CHECK: %[[C1_1:.*]] = llvm.mlir.constant(1 : i64) : i64
+// CHECK: %[[VEC1_1:.*]] = llvm.insertelement %[[ARG_3]], %[[VEC1_0]][%[[C1_1]] : i64] : vector<2xf32>
+// CHECK: %[[UNDEF_RES:.*]] = llvm.mlir.poison : !llvm.array<2 x array<1 x vector<2xf32>>>
+// CHECK: %[[RES_0:.*]] = llvm.insertvalue %[[VEC0_1]], %[[UNDEF_RES]][0, 0] : !llvm.array<2 x array<1 x vector<2xf32>>>
+// CHECK: %[[RES_1:.*]] = llvm.insertvalue %[[VEC1_1]], %[[RES_0]][1, 0] : !llvm.array<2 x array<1 x vector<2xf32>>>
+// CHECK: %[[CAST:.*]] = builtin.unrealized_conversion_cast %[[RES_1]] : !llvm.array<2 x array<1 x vector<2xf32>>> to vector<2x1x2xf32>
+// CHECK: return %[[CAST]]
+func.func @from_elements_3d(%arg0: f32, %arg1: f32, %arg2: f32, %arg3: f32) -> vector<2x1x2xf32> {
+ %0 = vector.from_elements %arg0, %arg1, %arg2, %arg3 : vector<2x1x2xf32>
+ return %0 : vector<2x1x2xf32>
+}
+
+// -----
+
//===----------------------------------------------------------------------===//
// vector.to_elements
//===----------------------------------------------------------------------===//
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