[libc-commits] [libc] [libc] implement `memalignment` (PR #132493)

[Joseph Huber via libc-commits]

================
@@ -0,0 +1,15 @@
+#include "src/stdlib/memalignment.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/CPP/bit.h"
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(size_t, memalignment, (const void *p)) {
+  if (p == nullptr)
+    return 0;
+
+  uintptr_t addr = reinterpret_cast<uintptr_t>(p);
+
+  return 1 << cpp::countr_zero(addr);
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jhuber6 wrote:

I decided on the original `addr & (~addr + 1)` version since it has better results for 64-bit.

https://github.com/llvm/llvm-project/pull/132493