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

[Gil Rapaport]

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@@ -77,6 +77,43 @@ 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();
+    auto 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(
+          allocOp.getLoc(), "cannot transform alloc op with dynamic shape");
+
+    // TODO: Is there a better API to determine the number of bits in a byte in
+    // MLIR?
+    int64_t totalSize = memrefType.getNumElements() *
+                        memrefType.getElementTypeBitWidth() / CHAR_BIT;
+    if (auto alignment = allocOp.getAlignment()) {
+      int64_t alignVal = alignment.value();
+      totalSize = (totalSize + alignVal - 1) / alignVal * alignVal;
+    }
+    mlir::Value sizeBytes = rewriter.create<emitc::ConstantOp>(
+        loc, rewriter.getIndexType(),
+        rewriter.getIntegerAttr(rewriter.getIndexType(), totalSize));
+    auto mallocPtrType = emitc::PointerType::get(rewriter.getContext(),
+                                                 memrefType.getElementType());
+    auto mallocCall = rewriter.create<emitc::CallOpaqueOp>(
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aniragil wrote:

IINM assigning in C++ a `void*` to, say, `int*` requires explicit casting or the -fpermissive compiler flag. Since we don't have a clear marking of the target C variant in the program we should probably emit an explicit cast as the common ground.

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