[llvm] [ADT] Simplify StringRef(const char *) (NFC) (PR #160038)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-adt

Author: Kazu Hirata (kazutakahirata)

<details>
<summary>Changes</summary>

This patch delegates the string length computation to
std::string_view.  This way, we don't have to worry about old GCC
versions or call __builtin_strlen on our own.


---
Full diff: https://github.com/llvm/llvm-project/pull/160038.diff


1 Files Affected:

- (modified) llvm/include/llvm/ADT/StringRef.h (+1-9) 


``````````diff
diff --git a/llvm/include/llvm/ADT/StringRef.h b/llvm/include/llvm/ADT/StringRef.h
index 16aca4d45892d..49a52fbe1a6f7 100644
--- a/llvm/include/llvm/ADT/StringRef.h
+++ b/llvm/include/llvm/ADT/StringRef.h
@@ -90,15 +90,7 @@ namespace llvm {
 
     /// Construct a string ref from a cstring.
     /*implicit*/ constexpr StringRef(const char *Str LLVM_LIFETIME_BOUND)
-        : Data(Str), Length(Str ?
-    // GCC 7 doesn't have constexpr char_traits. Fall back to __builtin_strlen.
-#if defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE < 8
-                                __builtin_strlen(Str)
-#else
-                                std::char_traits<char>::length(Str)
-#endif
-                                : 0) {
-    }
+        : StringRef(Str ? std::string_view(Str) : std::string_view()) {}
 
     /// Construct a string ref from a pointer and length.
     /*implicit*/ constexpr StringRef(const char *data LLVM_LIFETIME_BOUND,

``````````

</details>


https://github.com/llvm/llvm-project/pull/160038