[compiler-rt] [compiler-rt] Make sure __clzdi2 doesn't call itself recursively on sparc64 (PR #136737)

[Saleem Abdulrasool via llvm-commits]

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@@ -14,12 +14,12 @@
 
 // Returns: the number of leading 0-bits
 
-#if !defined(__clang__) &&                                                     \
-    ((defined(__sparc__) && defined(__arch64__)) || defined(__mips64) ||       \
+#if ((defined(__sparc__) && defined(__arch64__)) || defined(__mips64) ||       \
      (defined(__riscv) && __SIZEOF_POINTER__ >= 8))
 // On 64-bit architectures with neither a native clz instruction nor a native
-// ctz instruction, gcc resolves __builtin_clz to __clzdi2 rather than
+// ctz instruction, resolves __builtin_clz resolves to __clzdi2 rather than
 // __clzsi2, leading to infinite recursion.
+// This is because on those platforms, libgcc doesn't ship with __clzsi2.
----------------
compnerd wrote:

```suggestion
// `__clzsi2` as libgcc does not ship with `__clzsi2`, leading to infinite recursion.
```

https://github.com/llvm/llvm-project/pull/136737