[clang] [clang][bytecode] Load value of non-lvalue ArraySubscriptExpr (PR #160024)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/160024

As happens in C.

Fixes #158482

>From a00eb5e8b9b1267b8614c6fc8d0dfa419fb6f867 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Mon, 22 Sep 2025 05:01:46 +0200
Subject: [PATCH] [clang][bytecode] Load value of non-lvalue ArraySubscriptExpr

As happens in C.

Fixes #158482
---
 clang/lib/AST/ByteCode/Compiler.cpp | 7 ++++++-
 clang/test/AST/ByteCode/c.c         | 4 ++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index fafec47f7de3c..7518cfd2cf94d 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -1787,7 +1787,12 @@ bool Compiler<Emitter>::VisitArraySubscriptExpr(const ArraySubscriptExpr *E) {
     return false;
   if (DiscardResult)
     return this->emitPopPtr(E);
-  return true;
+
+  if (E->isGLValue())
+    return true;
+
+  OptPrimType T = classifyPrim(E);
+  return this->emitLoadPop(*T, E);
 }
 
 template <class Emitter>
diff --git a/clang/test/AST/ByteCode/c.c b/clang/test/AST/ByteCode/c.c
index 6681a4f427093..657a920e7d02c 100644
--- a/clang/test/AST/ByteCode/c.c
+++ b/clang/test/AST/ByteCode/c.c
@@ -368,3 +368,7 @@ void discardedCmp(void)
 {
     (*_b) = ((&a == &a) , a); // all-warning {{left operand of comma operator has no effect}}
 }
+
+/// ArraySubscriptExpr that's not an lvalue
+typedef unsigned char U __attribute__((vector_size(1)));
+void nonLValueASE(U f) { f[0] = f[((U)(U){0})[0]]; }