[Mlir-commits] [mlir] [mlir][ArmSME] Add rudimentary support for tile spills to the stack (PR #76086)

[Andrzej Warzyński]

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@@ -40,6 +132,209 @@ IntegerAttr getTileIdOrError(arm_sme::ArmSMETileOpInterface op) {
   return tileId;
 }
 
+/// Creates a alloca matching the size of tile used by `tileOp`. The alloca is
+/// placed in the first block of the function.
+static memref::AllocaOp
+createAllocaForTile(RewriterBase &rewriter, Location loc,
+                    FunctionOpInterface func,
+                    arm_sme::ArmSMETileOpInterface tileOp) {
+  RewriterBase::InsertionGuard g(rewriter);
+  // Move to the first operation in the function.
+  rewriter.setInsertionPoint(&func.getBlocks().front().front());
+  // Create an alloca matching the tile size of the `tileOp`.
+  auto vscale = rewriter.create<vector::VectorScaleOp>(loc);
+  auto tileElementType =
+      llvm::cast<VectorType>(tileOp.getTileType()).getElementType();
+  auto memrefType = MemRefType::get(
+      {ShapedType::kDynamic, ShapedType::kDynamic}, tileElementType);
+  auto minElements = arm_sme::getSMETileSliceMinNumElts(tileElementType);
+  auto minElementsOp =
+      rewriter.create<arith::ConstantIndexOp>(loc, minElements);
+  auto vectorLen = rewriter.create<arith::MulIOp>(loc, vscale, minElementsOp);
+  auto alloca = rewriter.create<memref::AllocaOp>(
+      loc, memrefType, ValueRange{vectorLen, vectorLen});
+  return alloca;
+}
+
+/// Finds or creates an alloca for a spill of a tile.
----------------
banach-space wrote:

So every Tile with a tileId > 16 will have a dedicated `alloca` created? Should this be checking `tileId` against so pre-defined constant (e.g. `kInMemoryTileIdBase`)?

https://github.com/llvm/llvm-project/pull/76086