[mlir][Target] Teach dense_resource conversion to LLVMIR Target

mlir/lib/Target/LLVMIR/ModuleTranslation.cpp

@@ -27,6 +27,7 @@
 #include "mlir/IR/Attributes.h"
 #include "mlir/IR/BuiltinOps.h"
 #include "mlir/IR/BuiltinTypes.h"
+#include "mlir/IR/DialectResourceBlobManager.h"
 #include "mlir/IR/RegionGraphTraits.h"
 #include "mlir/Support/LLVM.h"
 #include "mlir/Support/LogicalResult.h"
@@ -446,6 +447,90 @@ convertDenseElementsAttr(Location loc, DenseElementsAttr denseElementsAttr,
   return buildSequentialConstant(constantsRef, outerShape, llvmType, loc);
 }
 
+/// Convert a dense resource elements attribute to an LLVM IR constant using its
+/// raw data storage if possible. This supports elements attributes of tensor or
+/// vector type and avoids constructing separate objects for individual values
+/// of the innermost dimension. Constants for other dimensions are still
+/// constructed recursively. Returns null if constructing from raw data is not
+/// supported for this type, e.g., element type is not a power-of-two-sized
+/// primitive. Reports other errors at `loc`.
+static llvm::Constant *convertDenseResourceElementsAttr(
+    Location loc, DenseResourceElementsAttr denseResourceAttr,
+    llvm::Type *llvmType, const ModuleTranslation &moduleTranslation) {
+  if (!denseResourceAttr)
+    return nullptr;
+
+  llvm::Type *innermostLLVMType = getInnermostElementType(llvmType);
+  if (!llvm::ConstantDataSequential::isElementTypeCompatible(innermostLLVMType))
+    return nullptr;
+
+  ShapedType type = denseResourceAttr.getType();
+  if (type.getNumElements() == 0)
+    return nullptr;
+
+  ArrayRef<char> rawData =
+      denseResourceAttr.getRawHandle().getBlob()->getData();
+
+  // Check that the raw data size matches what is expected for the scalar size.
+  // TODO: in theory, we could repack the data here to keep constructing from
+  // raw data.
+  // TODO: we may also need to consider endianness when cross-compiling to an
+  // architecture where it is different.
+  int64_t numElements = denseResourceAttr.getType().getNumElements();
+  int64_t elementByteSize = rawData.size() / numElements;
+  if (8 * elementByteSize != innermostLLVMType->getScalarSizeInBits())
+    return nullptr;
+
+  // Compute the shape of all dimensions but the innermost. Note that the
+  // innermost dimension may be that of the vector element type.
+  bool hasVectorElementType = isa<VectorType>(type.getElementType());
+  int64_t numAggregates =
+      numElements / (hasVectorElementType
+                         ? 1
+                         : denseResourceAttr.getType().getShape().back());
+  ArrayRef<int64_t> outerShape = type.getShape();
+  if (!hasVectorElementType)
+    outerShape = outerShape.drop_back();
+
+  // Create a constructor for the innermost constant from a piece of raw data.
+  std::function<llvm::Constant *(StringRef)> buildCstData;
+  if (isa<TensorType>(type)) {
+    auto vectorElementType = dyn_cast<VectorType>(type.getElementType());
+    if (vectorElementType && vectorElementType.getRank() == 1) {
+      buildCstData = [&](StringRef data) {
+        return llvm::ConstantDataVector::getRaw(
+            data, vectorElementType.getShape().back(), innermostLLVMType);
+      };
+    } else if (!vectorElementType) {
+      buildCstData = [&](StringRef data) {
+        return llvm::ConstantDataArray::getRaw(data, type.getShape().back(),
+                                               innermostLLVMType);
+      };
+    }
+  } else if (isa<VectorType>(type)) {
+    buildCstData = [&](StringRef data) {
+      return llvm::ConstantDataVector::getRaw(data, type.getShape().back(),
+                                              innermostLLVMType);
+    };
+  }
+  if (!buildCstData)
+    return nullptr;
+
+  // Create innermost constants and defer to the default constant creation
+  // mechanism for other dimensions.
+  SmallVector<llvm::Constant *> constants;
+  int64_t aggregateSize = denseResourceAttr.getType().getShape().back() *
+                          (innermostLLVMType->getScalarSizeInBits() / 8);
+  constants.reserve(numAggregates);
+  for (unsigned i = 0; i < numAggregates; ++i) {
+    StringRef data(rawData.data() + i * aggregateSize, aggregateSize);
+    constants.push_back(buildCstData(data));
+  }
+
+  ArrayRef<llvm::Constant *> constantsRef = constants;
+  return buildSequentialConstant(constantsRef, outerShape, llvmType, loc);
+}
+
 /// Create an LLVM IR constant of `llvmType` from the MLIR attribute `attr`.
 /// This currently supports integer, floating point, splat and dense element
 /// attributes and combinations thereof. Also, an array attribute with two
@@ -546,6 +631,12 @@ llvm::Constant *mlir::LLVM::detail::getLLVMConstant(
     return result;
   }
 
+  if (llvm::Constant *result = convertDenseResourceElementsAttr(
+          loc, dyn_cast<DenseResourceElementsAttr>(attr), llvmType,
+          moduleTranslation)) {
+    return result;
+  }
+
   // Fall back to element-by-element construction otherwise.
   if (auto elementsAttr = dyn_cast<ElementsAttr>(attr)) {
     assert(elementsAttr.getShapedType().hasStaticShape());

mlir/test/Target/LLVMIR/llvmir.mlir

@@ -101,6 +101,9 @@ llvm.mlir.global internal @dense_float_vector_3d(dense<[[[1.0, 2.0], [3.0, 4.0]]
 // CHECK{LITERAL}: @splat_float_vector_3d = internal global [2 x [2 x <2 x float>]] [[2 x <2 x float>] [<2 x float> <float 4.200000e+01, float 4.200000e+01>, <2 x float> <float 4.200000e+01, float 4.200000e+01>], [2 x <2 x float>] [<2 x float> <float 4.200000e+01, float 4.200000e+01>, <2 x float> <float 4.200000e+01, float 4.200000e+01>]]
 llvm.mlir.global internal @splat_float_vector_3d(dense<42.0> : vector<2x2x2xf32>) : !llvm.array<2 x !llvm.array<2 x vector<2xf32>>>
 
+// CHECK: @dense_resource_constant = internal constant [5 x float] [float 0x3FCA034080000000, float 0xBFD0466300000000, float 0xBFD75DDF80000000, float 0xBFDE074F40000000, float 0x3FDDD3A1C0000000]
+llvm.mlir.global internal constant @dense_resource_constant(dense_resource<dense_resource_test> : tensor<5xf32>) : !llvm.array<5 x f32>
+
 //
 // Linkage attribute.
 //
@@ -1577,6 +1580,15 @@ llvm.func @invokeLandingpad() -> i32 attributes { personality = @__gxx_personali
   llvm.invoke %9(%6, %0) to ^bb2 unwind ^bb1 vararg(!llvm.func<void (ptr, ...)>) : !llvm.ptr, (!llvm.ptr, i32) -> ()
 }
 
+// Resources are kept at end of file. New tests should be added above this.
+{-#
+  dialect_resources: {
+    builtin: {
+      dense_resource_test: "0x08000000041A503E183382BEFCEEBABE7A3AF0BE0E9DEE3E"
+    }
+  }
+#-}
+
 // -----
 
 llvm.func @foo() -> i8