[Dynamic Shape] Erase expand (#60525)

* EraseExpandOp

* minor fix

* minor fix

* Code format

paddle/cinn/hlir/dialect/operator/transforms/group_merge/cinn_group_lowering_pass.cc

@@ -34,10 +34,85 @@
 #include "paddle/pir/pass/pass_registry.h"
 #include "paddle/pir/pattern_rewrite/frozen_rewrite_pattern_set.h"
 
+#include "paddle/fluid/pir/dialect/operator/ir/manual_op.h"
+#include "paddle/pir/dialect/shape/utils/dim_expr.h"
+
 PD_DECLARE_bool(cinn_enable_map_expr);
 
 namespace {
 
+using ShapeOrDataDimExprs4ValueT =
+    std::function<const symbol::ShapeOrDataDimExprs&(pir::Value)>;
+
+pir::Block::ConstIterator FindFirstExpandOp(pir::Block* block) {
+  for (auto iter = block->begin(); iter != block->end(); ++iter) {
+    if (iter->isa<paddle::dialect::ExpandOp>()) {
+      return iter;
+    }
+  }
+}
+
+bool SameInputOutputShape(
+    paddle::dialect::ExpandOp expand_op,
+    const ShapeOrDataDimExprs4ValueT& ShapeOrDataDimExprs4Value) {
+  const auto& x = ShapeOrDataDimExprs4Value(expand_op.x());
+  const auto& shape = ShapeOrDataDimExprs4Value(expand_op.shape());
+  const auto& out = ShapeOrDataDimExprs4Value(expand_op.out());
+  if (x.data().has_value()) return false;
+  if (!shape.data().has_value()) return false;
+  if (out.data().has_value()) return false;
+  CHECK(shape.data().value() == out.shape());
+  return x.shape() == out.shape();
+}
+
+void ReplaceAllUsesWithInput(paddle::dialect::ExpandOp expand) {
+  pir::Value x = expand.x();
+  expand.out().ReplaceAllUsesWith(x);
+}
+
+void EraseExpandOp(pir::Block* block, pir::Block::ConstIterator expand_it) {
+  block->erase(expand_it);
+}
+
+void EraseUpstreamGenerateShapeOp(
+    pir::Block* block, cinn::dialect::GenerateShapeOp generate_shape_op) {
+  for (auto iter = block->begin(); iter != block->end(); ++iter) {
+    if (iter->isa<cinn::dialect::GenerateShapeOp>()) {
+      if (iter->dyn_cast<cinn::dialect::GenerateShapeOp>() ==
+          generate_shape_op) {
+        block->erase(iter);
+      }
+    }
+  }
+}
+
+// Returns true if success
+bool EraseOneExpand(
+    pir::Block* block,
+    const ShapeOrDataDimExprs4ValueT& ShapeOrDataDimExprs4Value) {
+  for (auto expand_it = block->begin(); expand_it != block->end();
+       ++expand_it) {
+    if (!expand_it->isa<paddle::dialect::ExpandOp>()) continue;
+    auto expand = expand_it->dyn_cast<paddle::dialect::ExpandOp>();
+    if (!SameInputOutputShape(expand, ShapeOrDataDimExprs4Value)) continue;
+    auto generate_shape_op =
+        expand.shape().defining_op<cinn::dialect::GenerateShapeOp>();
+    CHECK_NOTNULL(generate_shape_op);
+    ReplaceAllUsesWithInput(expand);
+    EraseExpandOp(block, expand_it);
+    EraseUpstreamGenerateShapeOp(block, generate_shape_op);
+    return true;
+  }
+  return false;
+}
+
+void EraseExpands(pir::Block* block,
+                  const ShapeOrDataDimExprs4ValueT& ShapeOrDataDimExprs4Value) {
+  while (EraseOneExpand(block, ShapeOrDataDimExprs4Value)) {
+    // Do nothing.
+  }
+}
+
 std::vector<pir::Value> GetBlockOutsideInput(
     const std::vector<pir::Operation*> op_list) {
   std::vector<pir::Value> vec_res;