From fd79426050c9722d7dc601629b153a04068527b1 Mon Sep 17 00:00:00 2001
From: aadanen <aaron.danen@gmail.com>
Date: Fri, 11 Sep 2026 13:04:17 -0700
Subject: [PATCH] bitreverse implementation

fix and tests

fix tests
---
 cfg/gnu.cfg    | 73 +++++++++++++++++++++++++++++++++++++++++++++++++-
 test/cfg/gnu.c | 17 ++++++++++++
 2 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/cfg/gnu.cfg b/cfg/gnu.cfg
index f83ed44294a..197a1d33899 100644
--- a/cfg/gnu.cfg
+++ b/cfg/gnu.cfg
@@ -25,6 +25,7 @@
     <alloc init="false" buffer-size="malloc">pvalloc</alloc>
     <dealloc>free</dealloc>
   </memory>
+  <!-- https://gcc.gnu.org/onlinedocs/gcc/Byte-Swapping-Builtins.html -->
   <function name="bswap_16">
     <noreturn>false</noreturn>
     <use-retval/>
@@ -64,10 +65,80 @@
       <not-bool/>
     </arg>
   </function>
-  <define name="__builtin_bit_cast(type,value)" value="std::bit_cast&lt;type&gt;(value)"/>
   <define name="__bswap_constant_64(x)" value="bswap_64(x)"/>
   <define name="__builtin_bswap64(x)" value="bswap_64(x)"/>
   <define name="__bswap_64(x)" value="bswap_64(x)"/>
+  <function name="__builtin_bitreverse8">
+    <noreturn>false</noreturn>
+    <use-retval/>
+    <returnValue type="uint8_t">(arg1 = ((arg1 &amp; 0x55555555) &lt;&lt; 1) | ((arg1 &amp; 0xAAAAAAAA) &gt;&gt; 1),
+      arg1 = ((arg1 &amp; 0x33333333) &lt;&lt; 2) | ((arg1 &amp; 0xCCCCCCCC) &gt;&gt; 2),
+      arg1 = ((arg1 &amp; 0x0F0F0F0F) &lt;&lt; 4) | ((arg1 &amp; 0xF0F0F0F0) &gt;&gt; 4),
+      arg1)
+    </returnValue>
+    <leak-ignore/>
+    <const/>
+    <arg nr="1" direction="in">
+      <not-uninit/>
+      <not-bool/>
+      <valid>0:</valid>
+    </arg>
+  </function>
+  <function name="__builtin_bitreverse16">
+    <noreturn>false</noreturn>
+    <use-retval/>
+    <returnValue type="uint16_t">(arg1 = ((arg1 &amp; 0x55555555u) &lt;&lt; 1) | ((arg1 &amp; 0xAAAAAAAAu) &gt;&gt; 1),
+      arg1 = ((arg1 &amp; 0x33333333u) &lt;&lt; 2) | ((arg1 &amp; 0xCCCCCCCCu) &gt;&gt; 2),
+      arg1 = ((arg1 &amp; 0x0F0F0F0Fu) &lt;&lt; 4) | ((arg1 &amp; 0xF0F0F0F0u) &gt;&gt; 4),
+      arg1 = ((arg1 &amp; 0x00FF00FFu) &lt;&lt; 8) | ((arg1 &amp; 0xFF00FF00u) &gt;&gt; 8),
+      arg1)
+    </returnValue>
+    <leak-ignore/>
+    <const/>
+    <arg nr="1" direction="in">
+      <not-uninit/>
+      <not-bool/>
+      <valid>0:</valid>
+    </arg>
+  </function>
+  <function name="__builtin_bitreverse32">
+    <noreturn>false</noreturn>
+    <use-retval/>
+    <returnValue type="uint32_t">(arg1 = ((arg1 &amp; 0x55555555ul) &lt;&lt; 1) | ((arg1 &amp; 0xAAAAAAAAul) &gt;&gt; 1),
+      arg1 = ((arg1 &amp; 0x33333333ul) &lt;&lt; 2) | ((arg1 &amp; 0xCCCCCCCCul) &gt;&gt; 2),
+      arg1 = ((arg1 &amp; 0x0F0F0F0Ful) &lt;&lt; 4) | ((arg1 &amp; 0xF0F0F0F0ul) &gt;&gt; 4),
+      arg1 = ((arg1 &amp; 0x00FF00FFul) &lt;&lt; 8) | ((arg1 &amp; 0xFF00FF00ul) &gt;&gt; 8),
+      arg1 = ((arg1 &amp; 0x0000FFFFul) &lt;&lt; 16) | ((arg1 &amp; 0xFFFF0000ul) &gt;&gt; 16),
+      arg1)
+    </returnValue>
+    <leak-ignore/>
+    <const/>
+    <arg nr="1" direction="in">
+      <not-uninit/>
+      <not-bool/>
+      <valid>0:</valid>
+    </arg>
+  </function>
+  <function name="__builtin_bitreverse64">
+    <noreturn>false</noreturn>
+    <use-retval/>
+    <returnValue type="uint64_t">(arg1 = ((arg1 &amp; 0x55555555ull) &lt;&lt; 1) | ((arg1 &amp; 0xAAAAAAAAull) &gt;&gt; 1),
+      arg1 = ((arg1 &amp; 0x33333333ull) &lt;&lt; 2) | ((arg1 &amp; 0xCCCCCCCCull) &gt;&gt; 2),
+      arg1 = ((arg1 &amp; 0x0F0F0F0Full) &lt;&lt; 4) | ((arg1 &amp; 0xF0F0F0F0ull) &gt;&gt; 4),
+      arg1 = ((arg1 &amp; 0x00FF00FFull) &lt;&lt; 8) | ((arg1 &amp; 0xFF00FF00ull) &gt;&gt; 8),
+      arg1 = ((arg1 &amp; 0x0000FFFFull) &lt;&lt; 16) | ((arg1 &amp; 0xFFFF0000ull) &gt;&gt; 16),
+      arg1 = ((arg1 &amp; 0x00000000FFFFFFFFull) &lt;&lt; 32) | ((arg1 &amp; 0xFFFFFFFF00000000ull) &gt;&gt; 32),
+      arg1)
+    </returnValue>
+    <leak-ignore/>
+    <const/>
+    <arg nr="1" direction="in">
+      <not-uninit/>
+      <not-bool/>
+      <valid>0:</valid>
+    </arg>
+  </function>
+  <define name="__builtin_bit_cast(type,value)" value="std::bit_cast&lt;type&gt;(value)"/>
   <!-- https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html -->
   <define name="__builtin_alloca(size)" value="alloca(size)"/>
   <define name="__builtin_memcpy(dest, source, size)" value="memcpy(dest, source, size)"/>
diff --git a/test/cfg/gnu.c b/test/cfg/gnu.c
index 7b3c6ae5fed..db44a341779 100644
--- a/test/cfg/gnu.c
+++ b/test/cfg/gnu.c
@@ -390,6 +390,23 @@ void valid_code(int argInt1, va_list valist_arg, const int * parg)
     // cppcheck-suppress zerodiv
     // cppcheck-suppress unreadVariable
     i64_1 /= bswap_64(0x023456789abcde0f) - 0x0fdebc9a78563402;
+
+#if __GNUC__ > 16
+    uint8_t i8_1 = 0;
+    // cppcheck-suppress zerodiv
+    // cppcheck-suppress unreadVariable
+    i8_1 /= __builtin_bitreverse8(1) - 128;
+    // cppcheck-suppress zerodiv
+    // cppcheck-suppress unreadVariable
+    i16_1 /= __builtin_bitreverse16(5) - 40960;
+    // cppcheck-suppress zerodiv
+    // cppcheck-suppress unreadVariable
+    i32_1 /= __builtin_bitreverse32(4294967295) - 4294967295;
+    // cppcheck-suppress zerodiv
+    // cppcheck-suppress unreadVariable
+    i64_1 /= __builtin_bitreverse64(8) - 1152921504606846976;
+#endif
+
 #endif
 }