[clang-tools-extra] [clangd] Extract to function: Pass unmodified scalar parameters by value (PR #227675)

[Aleksandr Platonov via cfe-commits]

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@@ -1014,15 +1014,25 @@ bool createParameters(NewFunction &ExtractedFunc,
       return false;
     // Parameter qualifiers are same as the Decl's qualifiers.
     QualType TypeInfo = VD->getType().getNonReferenceType();
-    // Add const if it's not (conservatively) mutated in the zone: it's
-    // still passed by reference to avoid a copy, but the reference doesn't
-    // need to be mutable. Array types are never made const: mutating array
-    // elements through a non-const-ref loop variable or a decayed pointer
-    // argument is common and easy to miss conservatively, so we don't try.
-    if (!DeclInfo.IsPossiblyMutated && !TypeInfo->isArrayType())
-      TypeInfo.addConst();
     // FIXME: check if parameter will be a non l-value reference.
     bool IsPassedByReference = true;
+    if (!DeclInfo.IsPossiblyMutated) {
+      // A scalar (arithmetic, pointer, enumeration, ...) is at least as
+      // cheap to copy as to pass by reference, and less noisy. Any
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ArcsinX wrote:

I guess that for large scalar types this still makes sense to pass by reference.
E.g. `_BitInt(N)` is a scalar type. So, maybe we can add a check and still pass by reference if scalar type size ` > 2 * sizeof(void *)`

https://github.com/llvm/llvm-project/pull/227675