[clang] [clang][bytecode] Support composite arrays memcpy op (PR #132775)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/132775

See the attached test case.

>From f6be93ee0f3c9bfed4de7e1add7c2df9015ef12a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Mon, 24 Mar 2025 17:40:42 +0100
Subject: [PATCH] [clang][bytecode] Support composite arrays memcpy op

See the attached test case.
---
 clang/lib/AST/ByteCode/InterpBuiltin.cpp | 12 ++++++++++++
 clang/test/AST/ByteCode/c.c              | 10 ++++++++++
 2 files changed, 22 insertions(+)

diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index 5ea1d36a148ae..b305860d34f07 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -2793,6 +2793,18 @@ static bool copyComposite(InterpState &S, CodePtr OpPC, const Pointer &Src,
     return true;
   }
 
+  if (DestDesc->isCompositeArray()) {
+    assert(SrcDesc->isCompositeArray());
+    assert(SrcDesc->getNumElems() == DestDesc->getNumElems());
+    for (unsigned I = 0, N = DestDesc->getNumElems(); I != N; ++I) {
+      const Pointer &SrcElem = Src.atIndex(I).narrow();
+      Pointer DestElem = Dest.atIndex(I).narrow();
+      if (!copyComposite(S, OpPC, SrcElem, DestElem, Activate))
+        return false;
+    }
+    return true;
+  }
+
   if (DestDesc->isRecord())
     return copyRecord(S, OpPC, Src, Dest, Activate);
   return Invalid(S, OpPC);
diff --git a/clang/test/AST/ByteCode/c.c b/clang/test/AST/ByteCode/c.c
index 7cb7f96049f2d..fe47f9cab1c9f 100644
--- a/clang/test/AST/ByteCode/c.c
+++ b/clang/test/AST/ByteCode/c.c
@@ -203,6 +203,16 @@ const struct StrA sc = *sb;
 _Static_assert(sc.a == 12, ""); // pedantic-ref-warning {{GNU extension}} \
                                 // pedantic-expected-warning {{GNU extension}}
 
+struct ComplexS {
+  int a;
+  float b;
+  struct StrA sa[2];
+};
+const struct ComplexS CS = {12, 23.0f, {{1}, {2}}};
+const struct ComplexS CS2 = CS;
+_Static_assert(CS2.sa[0].a == 1, ""); // pedantic-ref-warning {{GNU extension}} \
+                                      // pedantic-expected-warning {{GNU extension}}
+
 _Static_assert(((void*)0 + 1) != (void*)0, ""); // pedantic-expected-warning {{arithmetic on a pointer to void is a GNU extension}} \
                                                 // pedantic-expected-warning {{not an integer constant expression}} \
                                                 // pedantic-expected-note {{cannot perform pointer arithmetic on null pointer}} \