[clang] [clang][Interp] Fix IntAP(s) to IntAP(s) casts (PR #69915)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr updated https://github.com/llvm/llvm-project/pull/69915

>From b82acd12f1217468d6fc53ab2b2f5856802b9b78 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Mon, 23 Oct 2023 12:46:25 +0200
Subject: [PATCH] [clang][Interp] Fix IntAP(s) to IntAP(s) casts

---
 clang/lib/AST/Interp/ByteCodeExprGen.cpp |  7 ++-----
 clang/test/AST/Interp/intap.cpp          | 11 +++++++++++
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/clang/lib/AST/Interp/ByteCodeExprGen.cpp b/clang/lib/AST/Interp/ByteCodeExprGen.cpp
index 485893d58f487ae..a2cf682b2532bde 100644
--- a/clang/lib/AST/Interp/ByteCodeExprGen.cpp
+++ b/clang/lib/AST/Interp/ByteCodeExprGen.cpp
@@ -200,16 +200,13 @@ bool ByteCodeExprGen<Emitter>::VisitCastExpr(const CastExpr *CE) {
     if (!this->visit(SubExpr))
       return false;
 
-    if (FromT == ToT) {
-      assert(ToT != PT_IntAP && ToT != PT_IntAPS);
-      return true;
-    }
-
     if (ToT == PT_IntAP)
       return this->emitCastAP(*FromT, Ctx.getBitWidth(CE->getType()), CE);
     if (ToT == PT_IntAPS)
       return this->emitCastAPS(*FromT, Ctx.getBitWidth(CE->getType()), CE);
 
+    if (FromT == ToT)
+      return true;
     return this->emitCast(*FromT, *ToT, CE);
   }
 
diff --git a/clang/test/AST/Interp/intap.cpp b/clang/test/AST/Interp/intap.cpp
index 02a860eb0986c15..c7df32b70d20a45 100644
--- a/clang/test/AST/Interp/intap.cpp
+++ b/clang/test/AST/Interp/intap.cpp
@@ -30,6 +30,17 @@ static_assert(UBitIntZero1 == 0, "");
 constexpr unsigned _BitInt(2) BI1 = 3u;
 static_assert(BI1 == 3, "");
 
+namespace APCast {
+  constexpr _BitInt(10) A = 1;
+  constexpr _BitInt(11) B = A;
+  static_assert(B == 1, "");
+  constexpr _BitInt(16) B2 = A;
+  static_assert(B2 == 1, "");
+  constexpr _BitInt(32) B3 = A;
+  static_assert(B3 == 1, "");
+  constexpr unsigned _BitInt(32) B4 = A;
+  static_assert(B4 == 1, "");
+}
 
 #ifdef __SIZEOF_INT128__
 namespace i128 {