[clang] [clang][bytecode] Initialize elements in __builtin_elementwise_popcount (PR #118457)

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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/118457.diff


2 Files Affected:

- (modified) clang/lib/AST/ByteCode/InterpBuiltin.cpp (+1) 
- (modified) clang/test/AST/ByteCode/builtin-functions.cpp (+12) 


``````````diff
diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index 2da16608e26c43..c5473322ecb280 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -1791,6 +1791,7 @@ static bool interp__builtin_elementwise_popcount(InterpState &S, CodePtr OpPC,
     INT_TYPE_SWITCH_NO_BOOL(ElemT, {
       Dst.atIndex(I).deref<T>() =
           T::from(Arg.atIndex(I).deref<T>().toAPSInt().popcount());
+      Dst.atIndex(I).initialize();
     });
   }
 
diff --git a/clang/test/AST/ByteCode/builtin-functions.cpp b/clang/test/AST/ByteCode/builtin-functions.cpp
index d8c8d207fbc45f..211ca6e164cbfb 100644
--- a/clang/test/AST/ByteCode/builtin-functions.cpp
+++ b/clang/test/AST/ByteCode/builtin-functions.cpp
@@ -7,6 +7,14 @@
 // RUN: %clang_cc1 -triple avr -std=c++20 -Wno-string-plus-int -fexperimental-new-constant-interpreter %s -verify=expected,both
 // RUN: %clang_cc1 -triple avr -std=c++20 -Wno-string-plus-int -verify=ref,both %s -Wno-constant-evaluated
 
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define LITTLE_END 1
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#define LITTLE_END 0
+#else
+#error "huh?"
+#endif
+
 extern "C" {
   typedef decltype(sizeof(int)) size_t;
   extern size_t wcslen(const wchar_t *p);
@@ -1140,6 +1148,10 @@ namespace ElementwisePopcount {
   static_assert(__builtin_elementwise_popcount(0L) == 0);
   static_assert(__builtin_elementwise_popcount(0xF0F0L) == 8);
   static_assert(__builtin_elementwise_popcount(~0LL) == 8 * sizeof(long long));
+
+#if __INT_WIDTH__ == 32
+  static_assert(__builtin_bit_cast(unsigned, __builtin_elementwise_popcount((vector4char){1, 2, 3, 4})) == (LITTLE_END ? 0x01020101 : 0x01010201));
+#endif
 }
 
 namespace BuiltinMemcpy {

``````````

</details>


https://github.com/llvm/llvm-project/pull/118457