[mlir] subview op lowering for target memrefs with const offset

The current standard to llvm conversion pass lowers subview ops only if
dynamic offsets are provided. This commit extends the lowering with a
code path that uses the constant offset of the target memref for the
subview op lowering (see Example 3 of the subview op definition for an
example) if no dynamic offsets are provided.

Differential Revision: https://reviews.llvm.org/D74280

diff --git a/mlir/lib/Conversion/StandardToLLVM/ConvertStandardToLLVM.cpp b/mlir/lib/Conversion/StandardToLLVM/ConvertStandardToLLVM.cpp
index 63c8b75f197f63c6944113759803b838cb33b1b3..36c98d0e85b156c39f366631a249f1aa6f81d425 100644 (file)
--- a/mlir/lib/Conversion/StandardToLLVM/ConvertStandardToLLVM.cpp
+++ b/mlir/lib/Conversion/StandardToLLVM/ConvertStandardToLLVM.cpp
@@ -2304,7 +2304,8 @@ struct SubViewOpLowering : public LLVMLegalizationPattern<SubViewOp> {
     // Currently, only rank > 0 and full or no operands are supported. Fail to
     // convert otherwise.
     unsigned rank = sourceMemRefType.getRank();
-    if (viewMemRefType.getRank() == 0 || (rank != dynamicOffsets.size()) ||
+    if (viewMemRefType.getRank() == 0 ||
+        (!dynamicOffsets.empty() && rank != dynamicOffsets.size()) ||
         (!dynamicSizes.empty() && rank != dynamicSizes.size()) ||
         (!dynamicStrides.empty() && rank != dynamicStrides.size()))
       return matchFailure();
@@ -2315,6 +2316,11 @@ struct SubViewOpLowering : public LLVMLegalizationPattern<SubViewOp> {
     if (failed(successStrides))
       return matchFailure();
 
+    // Fail to convert if neither a dynamic nor static offset is available.
+    if (dynamicOffsets.empty() &&
+        offset == MemRefType::getDynamicStrideOrOffset())
+      return matchFailure();
+
     // Create the descriptor.
     MemRefDescriptor sourceMemRef(operands.front());
     auto targetMemRef = MemRefDescriptor::undef(rewriter, loc, targetDescTy);
@@ -2348,14 +2354,18 @@ struct SubViewOpLowering : public LLVMLegalizationPattern<SubViewOp> {
     }
 
     // Offset.
-    Value baseOffset = sourceMemRef.offset(rewriter, loc);
-    for (int i = 0, e = viewMemRefType.getRank(); i < e; ++i) {
-      Value min = dynamicOffsets[i];
-      baseOffset = rewriter.create<LLVM::AddOp>(
-          loc, baseOffset,
-          rewriter.create<LLVM::MulOp>(loc, min, strideValues[i]));
+    if (dynamicOffsets.empty()) {
+      targetMemRef.setConstantOffset(rewriter, loc, offset);
+    } else {
+      Value baseOffset = sourceMemRef.offset(rewriter, loc);
+      for (int i = 0, e = viewMemRefType.getRank(); i < e; ++i) {
+        Value min = dynamicOffsets[i];
+        baseOffset = rewriter.create<LLVM::AddOp>(
+            loc, baseOffset,
+            rewriter.create<LLVM::MulOp>(loc, min, strideValues[i]));
+      }
+      targetMemRef.setOffset(rewriter, loc, baseOffset);
     }
-    targetMemRef.setOffset(rewriter, loc, baseOffset);
 
     // Update sizes and strides.
     for (int i = viewMemRefType.getRank() - 1; i >= 0; --i) {

diff --git a/mlir/test/Conversion/StandardToLLVM/convert-to-llvmir.mlir b/mlir/test/Conversion/StandardToLLVM/convert-to-llvmir.mlir
index 302aa31e48e0a95409bd7c91a5d6eb8893f00aa7..4c5a4a078a11e7f54e8015a3e9eb32a1d041b22d 100644 (file)
--- a/mlir/test/Conversion/StandardToLLVM/convert-to-llvmir.mlir
+++ b/mlir/test/Conversion/StandardToLLVM/convert-to-llvmir.mlir
@@ -815,6 +815,31 @@ func @subview_const_stride(%0 : memref<64x4xf32, affine_map<(d0, d1) -> (d0 * 4
   return
 }
 
+// CHECK-LABEL: func @subview_const_stride_and_offset(
+func @subview_const_stride_and_offset(%0 : memref<64x4xf32, affine_map<(d0, d1) -> (d0 * 4 + d1)>>) {
+  // The last "insertvalue" that populates the memref descriptor from the function arguments.
+  // CHECK: %[[MEMREF:.*]] = llvm.insertvalue %{{.*}}, %{{.*}}[4, 1]
+
+  // CHECK: %[[DESC:.*]] = llvm.mlir.undef : !llvm<"{ float*, float*, i64, [2 x i64], [2 x i64] }">
+  // CHECK: %[[DESC0:.*]] = llvm.insertvalue %{{.*}}, %[[DESC]][0] : !llvm<"{ float*, float*, i64, [2 x i64], [2 x i64] }">
+  // CHECK: %[[DESC1:.*]] = llvm.insertvalue %{{.*}}, %[[DESC0]][1] : !llvm<"{ float*, float*, i64, [2 x i64], [2 x i64] }">
+  // CHECK: %[[STRIDE0:.*]] = llvm.extractvalue %[[MEMREF]][4, 0] : !llvm<"{ float*, float*, i64, [2 x i64], [2 x i64] }">
+  // CHECK: %[[STRIDE1:.*]] = llvm.extractvalue %[[MEMREF]][4, 1] : !llvm<"{ float*, float*, i64, [2 x i64], [2 x i64] }">
+  // CHECK: %[[CST62:.*]] = llvm.mlir.constant(62 : i64)
+  // CHECK: %[[CST3:.*]] = llvm.mlir.constant(3 : i64)
+  // CHECK: %[[CST8:.*]] = llvm.mlir.constant(8 : index)
+  // CHECK: %[[DESC2:.*]] = llvm.insertvalue %[[CST8]], %[[DESC1]][2] : !llvm<"{ float*, float*, i64, [2 x i64], [2 x i64] }">
+  // CHECK: %[[DESC3:.*]] = llvm.insertvalue %[[CST3]], %[[DESC2]][3, 1] : !llvm<"{ float*, float*, i64, [2 x i64], [2 x i64] }">
+  // CHECK: %[[CST1:.*]] = llvm.mlir.constant(1 : i64)
+  // CHECK: %[[DESC4:.*]] = llvm.insertvalue %[[CST1]], %[[DESC3]][4, 1] : !llvm<"{ float*, float*, i64, [2 x i64], [2 x i64] }">
+  // CHECK: %[[DESC5:.*]] = llvm.insertvalue %[[CST62]], %[[DESC4]][3, 0] : !llvm<"{ float*, float*, i64, [2 x i64], [2 x i64] }">
+  // CHECK: %[[CST4:.*]] = llvm.mlir.constant(4 : i64)
+  // CHECK: llvm.insertvalue %[[CST4]], %[[DESC5]][4, 0] : !llvm<"{ float*, float*, i64, [2 x i64], [2 x i64] }">
+  %1 = subview %0[][][] :
+    memref<64x4xf32, affine_map<(d0, d1) -> (d0 * 4 + d1)>> to memref<62x3xf32, affine_map<(d0, d1) -> (d0 * 4 + d1 + 8)>>
+  return
+}
+
 // -----
 
 module {