From ce604df9e50f1702f7cb3320a48d1ef16d049fff Mon Sep 17 00:00:00 2001
From: gavin1012_hw <wanggang203@huawei.com>
Date: Tue, 19 Jul 2022 17:04:37 +0800
Subject: [PATCH] Support chain expression

Issue: I5IH79

Signed-off-by: gavin1012_hw <wanggang203@huawei.com>
Change-Id: I459aa005eedb7c2deb02ba958d4767585e7c888a
---
 es2panda/ir/expressions/chainExpression.cpp | 36 ++++++++++++++++++++-
 es2panda/ir/expressions/chainExpression.h   |  2 +-
 2 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/es2panda/ir/expressions/chainExpression.cpp b/es2panda/ir/expressions/chainExpression.cpp
index 16e2b3a299..6a49a01d90 100644
--- a/es2panda/ir/expressions/chainExpression.cpp
+++ b/es2panda/ir/expressions/chainExpression.cpp
@@ -14,8 +14,11 @@
  */
 
 #include "chainExpression.h"
+#include <compiler/core/pandagen.h>
 
 #include <ir/astDump.h>
+#include <ir/expressions/memberExpression.h>
+#include <ir/expressions/callExpression.h>
 
 namespace panda::es2panda::ir {
 
@@ -29,7 +32,38 @@ void ChainExpression::Dump(ir::AstDumper *dumper) const
     dumper->Add({{"type", "ChainExpression"}, {"expression", expression_}});
 }
 
-void ChainExpression::Compile([[maybe_unused]] compiler::PandaGen *pg) const {}
+void ChainExpression::Compile(compiler::PandaGen *pg) const
+{
+    // TODO: support continuous optional chain expression
+    compiler::RegScope rs(pg);
+    const MemberExpression *memberExpr = nullptr;
+    if (this->GetExpression()->IsMemberExpression()) {
+        memberExpr = this->GetExpression()->AsMemberExpression();
+    } else {
+        auto callExpr = this->GetExpression()->AsCallExpression();
+        memberExpr = callExpr->Callee()->AsMemberExpression();
+    }
+
+    compiler::VReg objReg = pg->AllocReg();
+    auto *isNullOrUndefinedLabel = pg->AllocLabel();
+    auto *endLabel = pg->AllocLabel();
+
+    memberExpr->CompileObject(pg, objReg);
+    pg->LoadConst(this, compiler::Constant::JS_NULL);
+    pg->Condition(this, lexer::TokenType::PUNCTUATOR_NOT_STRICT_EQUAL, objReg, isNullOrUndefinedLabel);
+    pg->LoadConst(this, compiler::Constant::JS_UNDEFINED);
+    pg->Condition(this, lexer::TokenType::PUNCTUATOR_NOT_STRICT_EQUAL, objReg, isNullOrUndefinedLabel);
+
+    // obj (ahead ?.) is not null/undefined, continue to compile sub-expression)
+    this->GetExpression()->Compile(pg);
+    pg->Branch(this, endLabel);
+
+    // obj (ahead ?.) is null/undefined, return undefined)
+    pg->SetLabel(this, isNullOrUndefinedLabel);
+    pg->LoadConst(this, compiler::Constant::JS_UNDEFINED);
+
+    pg->SetLabel(this, endLabel);
+}
 
 checker::Type *ChainExpression::Check([[maybe_unused]] checker::Checker *checker) const
 {
diff --git a/es2panda/ir/expressions/chainExpression.h b/es2panda/ir/expressions/chainExpression.h
index 571d10c89b..e31ed7c391 100644
--- a/es2panda/ir/expressions/chainExpression.h
+++ b/es2panda/ir/expressions/chainExpression.h
@@ -43,7 +43,7 @@ public:
 
     void Iterate(const NodeTraverser &cb) const override;
     void Dump(ir::AstDumper *dumper) const override;
-    void Compile([[maybe_unused]] compiler::PandaGen *pg) const override;
+    void Compile(compiler::PandaGen *pg) const override;
     checker::Type *Check([[maybe_unused]] checker::Checker *checker) const override;
 
 private:
-- 
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