[IR&PASS] fix constant_folding_pass and add use_count api for Value (#56967)

paddle/fluid/ir/transforms/constant_folding_pass.cc

@@ -92,14 +92,13 @@ class ConstantFoldingPattern : public ir::RewritePattern {
     }
 
     // Execute program
-    paddle::framework::interpreter::ExecutionConfig exe_config;
-    exe_config.create_local_scope = false;
+    exe_config_.create_local_scope = false;
     paddle::framework::InterpreterCore core(
         phi::CPUPlace{},
         fetch_var_names,
         paddle::dialect::PdOpLowerToKernelPass(temp_program.get()),
         &scope_,
-        exe_config);
+        exe_config_);
 
     paddle::framework::FetchList fetch_list = core.Run({});
 
@@ -112,6 +111,7 @@ class ConstantFoldingPattern : public ir::RewritePattern {
 
     std::string param_name =
         "@constant_folding_pass@_" + std::to_string(suffix_++);
+    exe_config_.skip_gc_vars.insert(param_name);
 
     auto* param_var = scope_.Var(param_name);
     auto* param_tensor = param_var->GetMutable<phi::DenseTensor>();
@@ -180,13 +180,11 @@ class ConstantFoldingPattern : public ir::RewritePattern {
   }
 
  private:
-  static size_t suffix_;
-  static paddle::framework::Scope scope_;
+  inline static size_t suffix_{0};
+  inline static paddle::framework::Scope scope_{};
+  inline static paddle::framework::interpreter::ExecutionConfig exe_config_{};
 };
 
-size_t ConstantFoldingPattern::suffix_ = 0;
-paddle::framework::Scope ConstantFoldingPattern::scope_ = {};
-
 class ConstantFoldingPass : public ir::Pass {
  public:
   // TODO(liuyuanle): Naming convention for pass.

paddle/ir/core/value.cc

@@ -13,6 +13,9 @@
 // limitations under the License.
 
 #include "paddle/ir/core/value.h"
+
+#include <cstddef>
+
 #include "paddle/ir/core/enforce.h"
 #include "paddle/ir/core/operation.h"
 #include "paddle/ir/core/value_impl.h"
@@ -128,6 +131,12 @@ bool Value::HasOneUse() const {
   return impl_->HasOneUse();
 }
 
+size_t Value::use_count() const {
+  size_t count = 0;
+  for (auto it = use_begin(); it != use_end(); ++it) count++;
+  return count;
+}
+
 void Value::ReplaceUsesWithIf(
     Value new_value,
     const std::function<bool(OpOperand)> &should_replace) const {

paddle/ir/core/value.h

@@ -123,6 +123,8 @@ class IR_API Value {
 
   bool HasOneUse() const;
 
+  size_t use_count() const;
+
   friend struct std::hash<Value>;
 
   void ReplaceUsesWithIf(

paddle/ir/pass/pass.h

@@ -78,7 +78,7 @@ class IR_API Pass {
 
   virtual ~Pass();
 
-  std::string name() const { return pass_info().name; }
+  const std::string& name() const { return pass_info().name; }
 
   const detail::PassInfo& pass_info() const { return pass_info_; }
 

paddle/ir/pattern_rewrite/pattern_rewrite_driver.cc

@@ -131,11 +131,15 @@ class GreedyPatternRewriteDriver : public ir::PatternRewriter {
     for (uint32_t i = 0; i < op->num_operands(); ++i) {
       AddOperandToWorklist(op->operand_source(i));
     }
-    for (uint32_t i = 0; i < op->num_regions(); ++i) {
-      auto& region = op->region(i);
-      for (auto& block : region) {
-        for (auto& op_item : *block) {
-          RemoveFromWorklist(op_item);
+    if (op->num_regions() == 0) {
+      RemoveFromWorklist(op);
+    } else {
+      for (uint32_t i = 0; i < op->num_regions(); ++i) {
+        auto& region = op->region(i);
+        for (auto& block : region) {
+          for (auto& op_item : *block) {
+            RemoveFromWorklist(op_item);
+          }
         }
       }
     }

test/cpp/ir/pattern_rewrite/pattern_rewrite_test.cc

@@ -1097,7 +1097,7 @@ TEST(pattern_rewrite, Patterns) {
 
   ir::PassManager pm(ctx);
   pm.AddPass(std::make_unique<TestPass>());
-  // pm.AddPass(ir::CreateConstantFoldingPass());
+  pm.AddPass(ir::CreateConstantFoldingPass());
   pm.AddPass(ir::CreateDeadCodeEliminationPass());
   pm.EnablePassTiming();
   pm.EnableIRPrinting();