[clang] [clang][bytecode] Don't get the expr without emitting a diagnostic (PR #141953)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Timm Baeder (tbaederr)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/141953.diff


1 Files Affected:

- (modified) clang/lib/AST/ByteCode/Interp.h (+2-1) 


``````````diff
diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h
index 5473733578d7e..33de09a263b3e 100644
--- a/clang/lib/AST/ByteCode/Interp.h
+++ b/clang/lib/AST/ByteCode/Interp.h
@@ -200,15 +200,16 @@ bool CheckShift(InterpState &S, CodePtr OpPC, const LT &LHS, const RT &RHS,
 
   if constexpr (Dir == ShiftDir::Left) {
     if (LHS.isSigned() && !S.getLangOpts().CPlusPlus20) {
-      const Expr *E = S.Current->getExpr(OpPC);
       // C++11 [expr.shift]p2: A signed left shift must have a non-negative
       // operand, and must not overflow the corresponding unsigned type.
       if (LHS.isNegative()) {
+        const Expr *E = S.Current->getExpr(OpPC);
         S.CCEDiag(E, diag::note_constexpr_lshift_of_negative) << LHS.toAPSInt();
         if (!S.noteUndefinedBehavior())
           return false;
       } else if (LHS.toUnsigned().countLeadingZeros() <
                  static_cast<unsigned>(RHS)) {
+        const Expr *E = S.Current->getExpr(OpPC);
         S.CCEDiag(E, diag::note_constexpr_lshift_discards);
         if (!S.noteUndefinedBehavior())
           return false;

``````````

</details>


https://github.com/llvm/llvm-project/pull/141953