[Mlir-commits] [mlir] [mlir][EmitC]Expand the MemRefToEmitC pass - Lowering `AllocOp` (PR #148257)

[Gil Rapaport]

================
@@ -77,6 +81,81 @@ struct ConvertAlloca final : public OpConversionPattern<memref::AllocaOp> {
   }
 };
 
+struct ConvertAlloc final : public OpConversionPattern<memref::AllocOp> {
+  using OpConversionPattern::OpConversionPattern;
+  LogicalResult
+  matchAndRewrite(memref::AllocOp allocOp, OpAdaptor operands,
+                  ConversionPatternRewriter &rewriter) const override {
+    mlir::Location loc = allocOp.getLoc();
+    MemRefType memrefType = allocOp.getType();
+    if (!memrefType.hasStaticShape()) {
+      // TODO: Handle Dynamic shapes in the future. If the size
+      // of the allocation is the result of some function, we could
+      // potentially evaluate the function and use the result in the call to
+      // allocate.
+      return rewriter.notifyMatchFailure(
+          loc, "cannot transform alloc with dynamic shape");
+    }
+
+    mlir::Type sizeTType = mlir::emitc::SizeTType::get(rewriter.getContext());
+    Type elementType = memrefType.getElementType();
+    mlir::emitc::CallOpaqueOp sizeofElementOp =
+        rewriter.create<mlir::emitc::CallOpaqueOp>(
+            loc, sizeTType, rewriter.getStringAttr("sizeof"),
+            mlir::ValueRange{},
+            mlir::ArrayAttr::get(rewriter.getContext(),
+                                 {mlir::TypeAttr::get(elementType)}));
+    mlir::Value sizeofElement = sizeofElementOp.getResult(0);
+
+    unsigned int elementWidth = elementType.getIntOrFloatBitWidth();
+    IntegerAttr indexAttr = rewriter.getIndexAttr(elementWidth);
+
+    mlir::Value numElements;
+    numElements = rewriter.create<emitc::ConstantOp>(
+        loc, rewriter.getIndexType(), indexAttr);
+    mlir::Value totalSizeBytes = rewriter.create<emitc::MulOp>(
+        loc, sizeTType, sizeofElement, numElements);
+
+    int64_t alignment = alignedAllocationGetAlignment(allocOp, elementWidth);
+    mlir::Value alignmentValue = rewriter.create<emitc::ConstantOp>(
+        loc, sizeTType,
+        rewriter.getIntegerAttr(rewriter.getIndexType(), alignment));
+
+    emitc::CallOpaqueOp alignedAllocCall = rewriter.create<emitc::CallOpaqueOp>(
+        loc,
+        emitc::PointerType::get(
+            mlir::emitc::OpaqueType::get(rewriter.getContext(), "void")),
+        rewriter.getStringAttr("aligned_alloc"),
+        mlir::ValueRange{alignmentValue, totalSizeBytes});
+    emitc::PointerType targetPointerType = emitc::PointerType::get(elementType);
+    emitc::CastOp castOp = rewriter.create<emitc::CastOp>(
+        loc, targetPointerType, alignedAllocCall.getResult(0));
----------------
aniragil wrote:

This part IMO should only be reached if there's actually an explicit alignment requirement. If there isn't any, better to emit a call to `malloc` and let the compiler use its native alignment rules. It would also work for lower versions than C11 C++17.

https://github.com/llvm/llvm-project/pull/148257