[Codegen] Fix if_then_else codegen (#16242)

* fix

* lint

* fix while loop

* clean

* clean

---------

Co-authored-by: Junru Shao <[email protected]>

Author: spectrometerHBH

src/target/source/codegen_c.cc

@@ -631,13 +631,33 @@ void CodeGenC::VisitExpr_(const CallNode* op, std::ostream& os) {  // NOLINT(*)
     } else if (op->op.same_as(builtin::shift_right())) {
       PrintBinaryIntrinsic(op, " >> ", os, this);
     } else if (op->op.same_as(builtin::if_then_else())) {
-      os << "(";
-      PrintExpr(op->args[0], os);
-      os << " ? ";
-      PrintExpr(op->args[1], os);
-      os << " : ";
-      PrintExpr(op->args[2], os);
-      os << ")";
+      // conditional that skips eval if cond evals to false
+      std::string result = name_supply_->FreshName("condval");
+      std::string cond = PrintExpr(op->args[0]);
+      this->PrintIndent();
+      PrintType(op->dtype, this->stream);
+      this->stream << " " << result << ";\n";
+      this->PrintIndent();
+      this->stream << "if (" << cond << ") {\n";
+      {
+        int then_scope = this->BeginScope();
+        std::string true_val = PrintExpr(op->args[1]);
+        this->PrintIndent();
+        this->stream << result << " = " << true_val << ";\n";
+        this->EndScope(then_scope);
+        this->PrintIndent();
+        this->stream << "} else {\n";
+      }
+      {
+        int else_scope = this->BeginScope();
+        std::string false_val = PrintExpr(op->args[2]);
+        this->PrintIndent();
+        this->stream << result << " = " << false_val << ";\n";
+        this->EndScope(else_scope);
+        this->PrintIndent();
+        this->stream << "}\n";
+      }
+      os << result;
     } else if (op->op.same_as(builtin::address_of())) {
       const BufferLoadNode* load = op->args[0].as<BufferLoadNode>();
       ICHECK(op->args.size() == 1 && load);
@@ -1022,8 +1042,11 @@ void CodeGenC::VisitStmt_(const ForNode* op) {
 
 void CodeGenC::VisitStmt_(const WhileNode* op) {
   PrintIndent();
-  stream << "while (" << PrintExpr(op->condition) << ") {\n";
+  stream << "while (1) {\n";
   int while_scope = BeginScope();
+  std::string cond = PrintExpr(op->condition);
+  PrintIndent();
+  stream << "if (!(" << cond << ")) { break; }\n";
   PrintStmt(op->body);
   this->EndScope(while_scope);
   PrintIndent();