From 5bc6ab006da7dbab993867c3d7d24cefaa81b51c Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 22 Feb 2023 08:08:11 -0700
Subject: [PATCH] Use __has_builtin for builtin checks instead of compiler
 versions

https://github.com/harfbuzz/harfbuzz/issues/4066#issuecomment-1439510188
---
 src/hb-algs.hh | 30 ++++++++++++++++++++++--------
 src/hb.hh      | 10 +++++++++-
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/src/hb-algs.hh b/src/hb-algs.hh
index e98645e3e..8c7ad434d 100644
--- a/src/hb-algs.hh
+++ b/src/hb-algs.hh
@@ -110,9 +110,10 @@ struct BEInt<Type, 2>
   constexpr operator Type () const
   {
 #if defined(__OPTIMIZE__) && !defined(HB_NO_PACKED) && \
-    ((defined(__GNUC__) && __GNUC__ >= 5) || defined(__clang__)) && \
     defined(__BYTE_ORDER) && \
-    (__BYTE_ORDER == __LITTLE_ENDIAN || __BYTE_ORDER == __BIG_ENDIAN)
+    (__BYTE_ORDER == __BIG_ENDIAN || \
+     (__BYTE_ORDER == __LITTLE_ENDIAN && \
+      hb_has_builtin(__builtin_bswap16)))
     /* Spoon-feed the compiler a big-endian integer with alignment 1.
      * https://github.com/harfbuzz/harfbuzz/pull/1398 */
 #if __BYTE_ORDER == __LITTLE_ENDIAN
@@ -155,9 +156,10 @@ struct BEInt<Type, 4>
   struct __attribute__((packed)) packed_uint32_t { uint32_t v; };
   constexpr operator Type () const {
 #if defined(__OPTIMIZE__) && !defined(HB_NO_PACKED) && \
-    ((defined(__GNUC__) && __GNUC__ >= 5) || defined(__clang__)) && \
     defined(__BYTE_ORDER) && \
-    (__BYTE_ORDER == __LITTLE_ENDIAN || __BYTE_ORDER == __BIG_ENDIAN)
+    (__BYTE_ORDER == __BIG_ENDIAN || \
+     (__BYTE_ORDER == __LITTLE_ENDIAN && \
+      hb_has_builtin(__builtin_bswap32)))
     /* Spoon-feed the compiler a big-endian integer with alignment 1.
      * https://github.com/harfbuzz/harfbuzz/pull/1398 */
 #if __BYTE_ORDER == __LITTLE_ENDIAN
@@ -598,13 +600,17 @@ template <typename T>
 static inline unsigned int
 hb_popcount (T v)
 {
-#if (defined(__GNUC__) && (__GNUC__ >= 4)) || defined(__clang__)
+#if hb_has_builtin(__builtin_popcount)
   if (sizeof (T) <= sizeof (unsigned int))
     return __builtin_popcount (v);
+#endif
 
+#if hb_has_builtin(__builtin_popcountl)
   if (sizeof (T) <= sizeof (unsigned long))
     return __builtin_popcountl (v);
+#endif
 
+#if hb_has_builtin(__builtin_popcountll)
   if (sizeof (T) <= sizeof (unsigned long long))
     return __builtin_popcountll (v);
 #endif
@@ -641,13 +647,17 @@ hb_bit_storage (T v)
 {
   if (unlikely (!v)) return 0;
 
-#if (defined(__GNUC__) && (__GNUC__ >= 4)) || defined(__clang__)
+#if hb_has_builtin(__builtin_clz)
   if (sizeof (T) <= sizeof (unsigned int))
     return sizeof (unsigned int) * 8 - __builtin_clz (v);
+#endif
 
+#if hb_has_builtin(__builtin_clzl)
   if (sizeof (T) <= sizeof (unsigned long))
     return sizeof (unsigned long) * 8 - __builtin_clzl (v);
+#endif
 
+#if hb_has_builtin(__builtin_clzll)
   if (sizeof (T) <= sizeof (unsigned long long))
     return sizeof (unsigned long long) * 8 - __builtin_clzll (v);
 #endif
@@ -715,13 +725,17 @@ hb_ctz (T v)
 {
   if (unlikely (!v)) return 8 * sizeof (T);
 
-#if (defined(__GNUC__) && (__GNUC__ >= 4)) || defined(__clang__)
+#if hb_has_builtin(__builtin_ctz)
   if (sizeof (T) <= sizeof (unsigned int))
     return __builtin_ctz (v);
+#endif
 
+#if hb_has_builtin(__builtin_ctzl)
   if (sizeof (T) <= sizeof (unsigned long))
     return __builtin_ctzl (v);
+#endif
 
+#if hb_has_builtin(__builtin_ctzll)
   if (sizeof (T) <= sizeof (unsigned long long))
     return __builtin_ctzll (v);
 #endif
@@ -875,7 +889,7 @@ hb_in_ranges (T u, T lo1, T hi1, Ts... ds)
 static inline bool
 hb_unsigned_mul_overflows (unsigned int count, unsigned int size, unsigned *result = nullptr)
 {
-#if (defined(__GNUC__) && (__GNUC__ >= 4)) || (defined(__clang__) && (__clang_major__ >= 8))
+#if hb_has_builtin(__builtin_mul_overflow)
   unsigned stack_result;
   if (!result)
     result = &stack_result;
diff --git a/src/hb.hh b/src/hb.hh
index 857571b42..d09849e56 100644
--- a/src/hb.hh
+++ b/src/hb.hh
@@ -246,7 +246,15 @@ extern "C" void  hb_free_impl(void *ptr);
  * Compiler attributes
  */
 
-#if (defined(__GNUC__) || defined(__clang__)) && defined(__OPTIMIZE__)
+// gcc 10 has __has_builtin but not earlier versions. Sanction any gcc >= 5
+// clang defines it so no need.
+#ifdef __has_builtin
+#define hb_has_builtin __has_builtin
+#else
+#define hb_has_builtin(x) ((defined(__GNUC__) && __GNUC__ >= 5))
+#endif
+
+#if defined(__OPTIMIZE__) && hb_has_builtin(__builtin_expect)
 #define likely(expr) (__builtin_expect (!!(expr), 1))
 #define unlikely(expr) (__builtin_expect (!!(expr), 0))
 #else