[clang] [clang][Interp] Fix assignment eval order (PR #101834)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: layta (cIamor)

<details>
<summary>Changes</summary>

RHS first

---
Full diff: https://github.com/llvm/llvm-project/pull/101834.diff


1 Files Affected:

- (modified) clang/lib/AST/Interp/Compiler.cpp (+12-4) 


``````````diff
diff --git a/clang/lib/AST/Interp/Compiler.cpp b/clang/lib/AST/Interp/Compiler.cpp
index ada22b569b2b0..d9db1c788314c 100644
--- a/clang/lib/AST/Interp/Compiler.cpp
+++ b/clang/lib/AST/Interp/Compiler.cpp
@@ -733,8 +733,8 @@ bool Compiler<Emitter>::VisitBinaryOperator(const BinaryOperator *BO) {
   }
 
   // Typecheck the args.
-  std::optional<PrimType> LT = classify(LHS->getType());
-  std::optional<PrimType> RT = classify(RHS->getType());
+  std::optional<PrimType> LT = classify(LHS);
+  std::optional<PrimType> RT = classify(RHS);
   std::optional<PrimType> T = classify(BO->getType());
 
   // Special case for C++'s three-way/spaceship operator <=>, which
@@ -769,8 +769,16 @@ bool Compiler<Emitter>::VisitBinaryOperator(const BinaryOperator *BO) {
       return this->VisitPointerArithBinOp(BO);
   }
 
-  if (!visit(LHS) || !visit(RHS))
-    return false;
+  // Assignmentes require us to evalute the RHS first.
+  if (BO->getOpcode() == BO_Assign) {
+    if (!visit(RHS) || !visit(LHS))
+      return false;
+    if (!this->emitFlip(*LT, *RT, BO))
+      return false;
+  } else {
+    if (!visit(LHS) || !visit(RHS))
+      return false;
+  }
 
   // For languages such as C, cast the result of one
   // of our comparision opcodes to T (which is usually int).

``````````

</details>


https://github.com/llvm/llvm-project/pull/101834