add stacking framework

decompiler/IR2/FormStack.cpp

@@ -0,0 +1,91 @@
+#include "FormStack.h"
+#include "Form.h"
+
+namespace decompiler {
+std::string FormStack::StackEntry::print(const Env& env) const {
+  if (destination.has_value()) {
+    assert(source && !elt);
+    return fmt::format("d: {} s: {} | {} <- {}", active, sequence_point,
+                       destination.value().reg().to_charp(), source->to_string(env));
+  } else {
+    assert(elt && !source);
+    return fmt::format("d: {} s: {} | {}", active, sequence_point, elt->to_string(env));
+  }
+}
+
+std::string FormStack::print(const Env& env) {
+  std::string result;
+  for (auto& x : m_stack) {
+    result += x.print(env);
+    result += '\n';
+  }
+  return result;
+}
+
+void FormStack::push_value_to_reg(Variable var, Form* value, bool sequence_point) {
+  StackEntry entry;
+  entry.active = true;  // by default, we should display everything!
+  entry.sequence_point = sequence_point;
+  entry.destination = var;
+  entry.source = value;
+  m_stack.push_back(entry);
+}
+
+bool FormStack::is_single_expression() {
+  int count = 0;
+  for (auto& e : m_stack) {
+    if (e.active) {
+      count++;
+    }
+  }
+  return count == 1;
+}
+
+void FormStack::push_form_element(FormElement* elt, bool sequence_point) {
+  StackEntry entry;
+  entry.active = true;
+  entry.elt = elt;
+  entry.sequence_point = sequence_point;
+  m_stack.push_back(entry);
+}
+
+Form* FormStack::pop_reg(const Variable& var) {
+  for (size_t i = m_stack.size(); i-- > 0;) {
+    auto& entry = m_stack.at(i);
+    if (entry.active) {
+      if (entry.destination == var) {
+        entry.active = false;
+        assert(entry.source);
+        return entry.source;
+      } else {
+        // we didn't match
+        if (entry.sequence_point) {
+          // and it's a sequence point! can't look any more back than this.
+          return nullptr;
+        }
+      }
+    }
+  }
+  // we didn't have it...
+  return nullptr;
+}
+
+std::vector<FormElement*> FormStack::rewrite(FormPool& pool) {
+  std::vector<FormElement*> result;
+
+  for (auto& e : m_stack) {
+    if (!e.active) {
+      continue;
+    }
+
+    if (e.destination.has_value()) {
+      auto elt = pool.alloc_element<SetVarElement>(*e.destination, e.source, e.sequence_point);
+      e.source->parent_element = elt;
+      result.push_back(elt);
+    } else {
+      result.push_back(e.elt);
+    }
+  }
+  return result;
+}
+}  // namespace decompiler