[mlir][vector] Refine Vector to LLVM lowering options

This is a follow-up to #144307, where we removed
`vector.matrix_multiply` and `vector.flat_transpose` from the Vector
dialect.

This PR:
* Updates comments that were missed in the previous change.
* Renames relevant `-convert-vector-to-llvm=` options:
  - `vector-contract-lowering=matmul` → `vector-contract-lowering=llvm`
  - `vector-transpose-lowering=flat_transpose` → `vector-transpose-lowering=llvm`

These new names better reflect the actual transformation target — LLVM
intrinsics — rather than the now-removed abstract operations.

Author: banach-space

mlir/include/mlir/Conversion/Passes.td

@@ -1489,8 +1489,8 @@ def ConvertVectorToLLVMPass : Pass<"convert-vector-to-llvm"> {
            VectorContractLoweringAttr.summary, [{::llvm::cl::values(
            clEnumValN(::mlir::vector::VectorContractLowering::Dot, "dot",
             "Progressively lower to finer grained `vector.contract` and dot-products. (default)"),
-           clEnumValN(::mlir::vector::VectorContractLowering::Matmul, "matmul",
-            "Lower to `vector.matrix_multiply`, maps 1-1 to LLVM matrix intrinsics."),
+           clEnumValN(::mlir::vector::VectorContractLowering::LLVM, "llvm",
+            "Lower directly to `llvm.intr.matrix.multiply`."),
            clEnumValN(::mlir::vector::VectorContractLowering::OuterProduct, "outerproduct",
             "Lower to `vector.outerproduct`."),
            clEnumValN(::mlir::vector::VectorContractLowering::ParallelArith, "parallelarith",
@@ -1502,8 +1502,8 @@ def ConvertVectorToLLVMPass : Pass<"convert-vector-to-llvm"> {
            VectorTransposeLoweringAttr.summary, [{::llvm::cl::values(
            clEnumValN(::mlir::vector::VectorTransposeLowering::EltWise, "eltwise",
             "Lower transpose into element-wise extract and inserts (default)"),
-           clEnumValN(::mlir::vector::VectorTransposeLowering::Flat, "flat",
-            "Lower 2-D transpose to `vector.flat_transpose`, maps 1-1 to LLVM matrix intrinsics"),
+           clEnumValN(::mlir::vector::VectorTransposeLowering::LLVM, "llvm",
+            "Lower 2-D transpose directly to `llvm.intr.matrix.transpose`"),
            clEnumValN(::mlir::vector::VectorTransposeLowering::Shuffle1D, "shuffle1d",
             "Lower 2-D transpose to `vector.shuffle` on 1-D vector."),
            clEnumValN(::mlir::vector::VectorTransposeLowering::Shuffle16x16, "shuffle16x16",

mlir/include/mlir/Dialect/Vector/Transforms/VectorTransformsBase.td

@@ -14,10 +14,9 @@ include "mlir/IR/EnumAttr.td"
 // Lower transpose into element-wise extract and inserts.
 def VectorTransposeLowering_Elementwise:
   I32EnumAttrCase<"EltWise",  0, "eltwise">;
-// Lower 2-D transpose to `vector.flat_transpose`, maps 1-1 to LLVM matrix
-// intrinsics.
-def VectorTransposeLowering_FlatTranspose:
-  I32EnumAttrCase<"Flat",  1, "flat_transpose">;
+// Lower directly to LLVM matrix intrinsics.
+def VectorTransposeLowering_LLVM:
+  I32EnumAttrCase<"LLVM",  1, "llvm">;
 // Lower 2-D transpose to `vector.shuffle` on 1-D vector.
 def VectorTransposeLowering_Shuffle1D:
   I32EnumAttrCase<"Shuffle1D",  2, "shuffle_1d">;
@@ -27,7 +26,7 @@ def VectorTransposeLowering_Shuffle16x16:
 def VectorTransposeLoweringAttr : I32EnumAttr<
     "VectorTransposeLowering",
     "control the lowering of `vector.transpose` operations.",
-    [VectorTransposeLowering_Elementwise, VectorTransposeLowering_FlatTranspose,
+    [VectorTransposeLowering_Elementwise, VectorTransposeLowering_LLVM,
      VectorTransposeLowering_Shuffle1D, VectorTransposeLowering_Shuffle16x16]> {
   let cppNamespace = "::mlir::vector";
 }
@@ -48,9 +47,9 @@ def VectorMultiReductionLoweringAttr: I32EnumAttr<
 
 // Progressively lower to finer grained `vector.contract` and dot-products.
 def VectorContractLowering_Dot: I32EnumAttrCase<"Dot", 0, "dot">;
-// Lower to `vector.matrix_multiply`, maps 1-1 to LLVM matrix intrinsics.
-def VectorContractLowering_Matmul:
-  I32EnumAttrCase<"Matmul", 1, "matmulintrinsics">;
+// Lower directly to LLVM intrinsics. 
+def VectorContractLowering_LLVM:
+  I32EnumAttrCase<"LLVM", 1, "llvm">;
 // Lower to `vector.outerproduct`.
 def VectorContractLowering_OuterProduct:
   I32EnumAttrCase<"OuterProduct", 2, "outerproduct">;
@@ -61,7 +60,7 @@ def VectorContractLowering_ParallelArith:
 def VectorContractLoweringAttr: I32EnumAttr<
     "VectorContractLowering",
     "control the lowering of `vector.contract` operations.",
-  [VectorContractLowering_Dot, VectorContractLowering_Matmul,
+  [VectorContractLowering_Dot, VectorContractLowering_LLVM,
    VectorContractLowering_OuterProduct, VectorContractLowering_ParallelArith]> {
   let cppNamespace = "::mlir::vector";
 }

mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVM.cpp

@@ -1987,16 +1987,12 @@ struct VectorScalableStepOpLowering
 ///    %e = add %c, %d
 /// ```
 /// `vector.matrix_multiply` later lowers to `llvm.matrix.multiply`.
-//
-/// This only kicks in when vectorContractLowering is set to Matmul and
-/// the vector.contract op is a row-major matrix multiply.
 class ContractionOpToMatmulOpLowering
     : public vector::MaskableOpRewritePattern<vector::ContractionOp> {
 public:
   using MaskableOpRewritePattern::MaskableOpRewritePattern;
 
   ContractionOpToMatmulOpLowering(
-      vector::VectorContractLowering vectorContractLowering,
       MLIRContext *context, PatternBenefit benefit = 100)
       : MaskableOpRewritePattern<vector::ContractionOp>(context, benefit) {}
 
@@ -2005,23 +2001,22 @@ class ContractionOpToMatmulOpLowering
                             PatternRewriter &rewriter) const override;
 };
 
-/// Progressively lower a `vector.contract %a, %b, %c` with row-major matmul
-/// semantics to:
+/// Lower a qualifying `vector.contract %a, %b, %c` (with row-major matmul
+/// semantics directly into `llvm.intr.matrix.multiply`:
+/// BEFORE:
 /// ```
-///    %mta = maybe_transpose
-///    %mtb = maybe_transpose
-///    %flattened_a = vector.shape_cast %mta
-///    %flattened_b = vector.shape_cast %mtb
-///    %flattened_d = llvm.intr.matrix.multiply %flattened_a, %flattened_b
-///    %mtd = vector.shape_cast %flattened_d
-///    %d = maybe_untranspose %mtd
-///    %e = add %c, %d
+///  %res = vector.contract #matmat_trait %lhs, %rhs, %acc
+///    : vector<2x4xf32>, vector<4x3xf32> into vector<2x3xf32>
 /// ```
-//
-/// This only kicks in when vectorContractLowering is set to `Matmul`.
-/// vector.transpose operations are inserted if the vector.contract op is not a
-/// row-major matrix multiply.
 ///
+/// AFTER:
+/// ```
+///   %lhs = vector.shape_cast %arg0 : vector<2x4xf32> to vector<8xf32>
+///   %rhs = vector.shape_cast %arg1 : vector<4x3xf32> to vector<12xf32>
+///   %matmul = llvm.intr.matrix.multiply %lhs, %rhs
+///   %res = arith.addf %acc, %matmul : vector<2x3xf32>
+/// ```
+//
 /// Scalable vectors are not supported.
 FailureOr<Value> ContractionOpToMatmulOpLowering::matchAndRewriteMaskableOp(
     vector::ContractionOp op, MaskingOpInterface maskOp,
@@ -2116,7 +2111,19 @@ FailureOr<Value> ContractionOpToMatmulOpLowering::matchAndRewriteMaskableOp(
   return res;
 }
 
-/// Lowers vector.transpose to llvm.intr.matrix.transpose
+/// Lowers vector.transpose directly to llvm.intr.matrix.transpose
+///
+/// BEFORE:
+/// ```
+///  %tr = vector.transpose %vec, [1, 0] : vector<2x4xf32> to vector<4x2xf32>
+/// ```
+/// AFTER:
+/// ```
+///  %vec_cs = vector.shape_cast %vec : vector<2x4xf32> to vector<8xf32>
+///  %tr = llvm.intr.matrix.transpose %vec_sc
+///    {columns = 2 : i32, rows = 4 : i32} : vector<8xf32> into vector<8xf32>
+///  %res = vector.shape_cast %tr : vector<8xf32> to vector<4x2xf32>
+/// ```
 class TransposeOpToMatrixTransposeOpLowering
     : public OpRewritePattern<vector::TransposeOp> {
 public:

mlir/lib/Conversion/VectorToLLVM/ConvertVectorToLLVMPass.cpp

@@ -70,7 +70,7 @@ void ConvertVectorToLLVMPass::runOnOperation() {
     populateVectorBitCastLoweringPatterns(patterns);
     populateVectorBroadcastLoweringPatterns(patterns);
     populateVectorContractLoweringPatterns(patterns, vectorContractLowering);
-    if (vectorContractLowering == vector::VectorContractLowering::Matmul) {
+    if (vectorContractLowering == vector::VectorContractLowering::LLVM) {
       // This pattern creates a dependency on the LLVM dialect, hence we don't
       // include it in `populateVectorContractLoweringPatterns` that is part of
       // the Vector dialect (and should not depend on LLVM).
@@ -80,7 +80,7 @@ void ConvertVectorToLLVMPass::runOnOperation() {
     populateVectorShapeCastLoweringPatterns(patterns);
     populateVectorInterleaveLoweringPatterns(patterns);
     populateVectorTransposeLoweringPatterns(patterns, vectorTransposeLowering);
-    if (vectorTransposeLowering == vector::VectorTransposeLowering::Flat) {
+    if (vectorTransposeLowering == vector::VectorTransposeLowering::LLVM) {
       // This pattern creates a dependency on the LLVM dialect, hence we don't
       // include it in `populateVectorTransposeLoweringPatterns` that is part of
       // the Vector dialect (and should not depend on LLVM).

mlir/test/Conversion/VectorToLLVM/pass-option-serialization.mlir

@@ -13,7 +13,7 @@
 
 // RUN: mlir-opt --convert-vector-to-llvm --dump-pass-pipeline %s 2>&1 | FileCheck %s --check-prefix=DEFAULT
 
-// RUN: mlir-opt --convert-vector-to-llvm='vector-contract-lowering=matmul vector-transpose-lowering=flat' \
+// RUN: mlir-opt --convert-vector-to-llvm='vector-contract-lowering=llvm vector-transpose-lowering=llvm' \
 // RUN:          --dump-pass-pipeline %s 2>&1 | FileCheck %s --check-prefix=NON-DEFAULT
 
 // CHECK: builtin.module(
@@ -26,5 +26,5 @@
 // CHECK-SAME: reassociate-fp-reductions={{[aA-zZ0-9]+}}
 // DEFAULT: vector-contract-lowering=dot
 // DEFAULT: vector-transpose-lowering=eltwise
-// NON-DEFAULT: vector-contract-lowering=matmul
-// NON-DEFAULT: vector-transpose-lowering=flat
+// NON-DEFAULT: vector-contract-lowering=llvm
+// NON-DEFAULT: vector-transpose-lowering=llvm

mlir/test/Dialect/Vector/vector-contract-to-matrix-intrinsics-transforms.mlir

@@ -1,4 +1,4 @@
-// RUN: mlir-opt %s  --convert-vector-to-llvm='vector-contract-lowering=matmul' | FileCheck %s
+// RUN: mlir-opt %s  --convert-vector-to-llvm='vector-contract-lowering=llvm' | FileCheck %s
 
 #matmat_accesses = [
   affine_map<(i, j, k) -> (i, k)>,

mlir/test/Dialect/Vector/vector-transpose-to-matrix-intrinsics-transform.mlir

@@ -1,4 +1,4 @@
-// RUN: mlir-opt %s --convert-vector-to-llvm='vector-transpose-lowering=flat' --split-input-file | FileCheck %s
+// RUN: mlir-opt %s --convert-vector-to-llvm='vector-transpose-lowering=llvm' --split-input-file | FileCheck %s
 
 // CHECK-LABEL: func @transpose(
 func.func @transpose(%arg0: vector<2x4xf32>) -> vector<4x2xf32> {