[Triton-MLIR] Replace triton.extract_slice with tensor.extract_slice and support more general tensor slicing (#837)

## Features

- Allow taking a block of tensor slice, as long as each dimension is
contiguous (unit stride).
- Fix some problems in `insert_slice_async`'s semantic.
- More general verification for ops that return shared layout encoding.

## Known Limitations

- `insert_slice_async` still uses the old semantic. May submit another
PR later to support similar semantic like `tensor.extract_slice`.
- No encoding verification for `tensor.extract_slice`.
- 3d tensor ops are broken.
- Strided accesses are not allowed.
- May cause a little performance slowdown since we are passing strides
as values but not constants (e.g., int).
It would be difficult to pass strides as attributes when we have control
flows. A block argument is possible to accept tensors with different
strides.

lib/Analysis/Alias.cpp

@@ -1,4 +1,5 @@
 #include "triton/Analysis/Alias.h"
+#include "mlir/Dialect/Tensor/IR/Tensor.h"
 #include "triton/Analysis/Utility.h"
 #include "triton/Dialect/TritonGPU/IR/Dialect.h"
 
@@ -24,18 +25,18 @@ ChangeResult SharedMemoryAliasAnalysis::visitOperation(
   if (maybeSharedAllocationOp(op)) {
     // These ops may allocate a new shared memory buffer.
     auto result = op->getResult(0);
-    if (isSharedEncoding(result)) {
-      // FIXME(Keren): extract and insert are always alias for now
-      if (auto extractSliceOp = dyn_cast<triton::gpu::ExtractSliceOp>(op)) {
-        // extract_slice %src, %index
-        aliasInfo = AliasInfo(operands[0]->getValue());
-      } else if (auto insertSliceOp =
-                     dyn_cast<triton::gpu::InsertSliceAsyncOp>(op)) {
-        // insert_slice_async %src, %dst, %index
-        aliasInfo = AliasInfo(operands[1]->getValue());
-      } else {
-        aliasInfo.insert(result);
-      }
+    // FIXME(Keren): extract and insert are always alias for now
+    if (auto extractSliceOp = dyn_cast<tensor::ExtractSliceOp>(op)) {
+      // extract_slice %src
+      aliasInfo = AliasInfo(operands[0]->getValue());
+      pessimistic = false;
+    } else if (auto insertSliceOp =
+                   dyn_cast<triton::gpu::InsertSliceAsyncOp>(op)) {
+      // insert_slice_async %src, %dst, %index
+      aliasInfo = AliasInfo(operands[1]->getValue());
+      pessimistic = false;
+    } else if (isSharedEncoding(result)) {
+      aliasInfo.insert(result);
       pessimistic = false;
     }
   }