From b81b64a961fc23fb3466d2a71a542803c9c55fcc Mon Sep 17 00:00:00 2001
From: Matevz Kovacic <117923752+matevz-kovacic@users.noreply.github.com>
Date: Thu, 6 Aug 2026 08:49:46 +0200
Subject: [PATCH 1/2] compiler: apply TARGET_ATTRIBUTE under clang-cl, not only
 under __GNUC__

portability_macros.h enables DYNAMIC_BMI2 for clang-cl by testing
__clang__ && __has_attribute(__target__). compiler.h then gates
TARGET_ATTRIBUTE on __GNUC__, which clang-cl does not define, so
BMI2_TARGET_ATTRIBUTE expands to nothing and the dispatched _bmi2
entry points are compiled without BMI2.

Test the attribute directly with __has_attribute, keeping the __GNUC__
test as a fallback for compilers without __has_attribute. No change on
any compiler that defines __GNUC__.
---
 lib/common/compiler.h | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/lib/common/compiler.h b/lib/common/compiler.h
index 5e70570ec7a..1351495997f 100644
--- a/lib/common/compiler.h
+++ b/lib/common/compiler.h
@@ -118,8 +118,26 @@
 #endif
 
 
-/* target attribute */
-#if defined(__GNUC__) || defined(__IAR_SYSTEMS_ICC__)
+/* target attribute
+ *
+ * This condition must stay in sync with the one DYNAMIC_BMI2 uses in
+ * portability_macros.h. clang in MSVC-compatible mode (clang-cl) supports
+ * __attribute__((__target__)) but does not define __GNUC__, so testing
+ * __GNUC__ alone silently expands this to nothing while DYNAMIC_BMI2
+ * remains enabled -- the runtime dispatch then calls _bmi2 entry points
+ * that were compiled with no BMI2 at all.
+ */
+#if defined(__has_attribute)
+#  if __has_attribute(__target__)
+#    define ZSTD_HAS_TARGET_ATTRIBUTE 1
+#  endif
+#endif
+#if !defined(ZSTD_HAS_TARGET_ATTRIBUTE) && \
+    (defined(__GNUC__) || defined(__IAR_SYSTEMS_ICC__))
+#  define ZSTD_HAS_TARGET_ATTRIBUTE 1
+#endif
+
+#if defined(ZSTD_HAS_TARGET_ATTRIBUTE)
 #  define TARGET_ATTRIBUTE(target) __attribute__((__target__(target)))
 #else
 #  define TARGET_ATTRIBUTE(target)

From 4afc10ef28d9df8b212dbeb28d0ea4dab6519699 Mon Sep 17 00:00:00 2001
From: Matevz Kovacic <117923752+matevz-kovacic@users.noreply.github.com>
Date: Thu, 6 Aug 2026 08:49:52 +0200
Subject: [PATCH 2/2] compiler: honour LIKELY/UNLIKELY under clang-cl

Same __GNUC__ gate as TARGET_ATTRIBUTE. clang-cl supports
__builtin_expect, so test for it with __has_builtin and keep __GNUC__
as a fallback. Without this, every branch hint in the library is
discarded under clang-cl.
---
 lib/common/compiler.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/common/compiler.h b/lib/common/compiler.h
index 1351495997f..2cb8b1615aa 100644
--- a/lib/common/compiler.h
+++ b/lib/common/compiler.h
@@ -201,7 +201,16 @@
  * If you can remove a LIKELY/UNLIKELY annotation without speed changes in gcc
  * and clang, please do.
  */
-#if defined(__GNUC__)
+#if defined(__has_builtin)
+#  if __has_builtin(__builtin_expect)
+#    define ZSTD_HAS_BUILTIN_EXPECT 1
+#  endif
+#endif
+#if !defined(ZSTD_HAS_BUILTIN_EXPECT) && defined(__GNUC__)
+#  define ZSTD_HAS_BUILTIN_EXPECT 1
+#endif
+
+#if defined(ZSTD_HAS_BUILTIN_EXPECT)
 #define LIKELY(x) (__builtin_expect((x), 1))
 #define UNLIKELY(x) (__builtin_expect((x), 0))
 #else