[clangd] Tune down scope boost for global scope

Summary:
This improves cross-namespace completions and has ignorable
impact on other completion types.

Metrics
```
==================================================================================================
                                        OVERALL (excl. CROSS_NAMESPACE)
==================================================================================================
  Total measurements: 109367 (-6)
  All measurements:
	MRR: 68.11 (+0.04)	Top-1: 58.59% (+0.03%)	Top-5: 80.00% (+0.01%)	Top-100: 95.92% (-0.02%)
  Full identifiers:
	MRR: 98.35 (+0.09)	Top-1: 97.87% (+0.17%)	Top-5: 98.96% (+0.01%)	Top-100: 99.03% (+0.00%)
  Filter length 0-5:
	MRR:      23.20 (+0.05)		58.72 (+0.01)		70.16 (-0.03)		73.44 (+0.03)		76.24 (+0.00)		80.79 (+0.14)
	Top-1:    11.90% (+0.03%)		45.07% (+0.03%)		58.49% (-0.05%)		62.44% (-0.02%)		66.31% (-0.05%)		72.10% (+0.07%)
	Top-5:    35.51% (+0.08%)		76.94% (-0.01%)		85.10% (-0.13%)		87.40% (-0.02%)		88.65% (+0.01%)		91.84% (+0.17%)
	Top-100:  83.25% (-0.02%)		96.61% (-0.15%)		98.15% (-0.02%)		98.43% (-0.01%)		98.53% (+0.01%)		98.66% (+0.02%)

==================================================================================================
                                        CROSS_NAMESPACE
==================================================================================================
  Total measurements: 17702 (+27)
  All measurements:
	MRR: 28.12 (+3.26)	Top-1: 21.07% (+2.70%)	Top-5: 35.11% (+4.48%)	Top-100: 74.31% (+1.02%)
  Full identifiers:
	MRR: 79.20 (+3.72)	Top-1: 71.78% (+4.86%)	Top-5: 88.39% (+2.84%)	Top-100: 98.99% (+0.00%)
  Filter length 0-5:
	MRR:      0.92 (-0.10)		5.51 (+0.57)		18.30 (+2.34)		21.62 (+3.76)		32.00 (+6.00)		41.55 (+7.61)
	Top-1:    0.56% (-0.08%)		2.44% (+0.15%)		9.82% (+1.47%)		12.59% (+2.16%)		21.17% (+4.47%)		30.05% (+6.72%)
	Top-5:    1.20% (-0.15%)		7.14% (+1.04%)		25.17% (+3.91%)		29.74% (+5.90%)		43.29% (+9.59%)		54.75% (+9.79%)
	Top-100:  5.49% (-0.01%)		56.22% (+2.59%)		86.69% (+1.08%)		89.03% (+2.04%)		93.74% (+0.78%)		96.99% (+0.59%)
```

Reviewers: sammccall

Reviewed By: sammccall

Subscribers: ilya-biryukov, MaskRay, jkorous, arphaman, kadircet, cfe-commits

Differential Revision: https://reviews.llvm.org/D54851

llvm-svn: 347548

diff --git a/clang-tools-extra/clangd/FileDistance.cpp b/clang-tools-extra/clangd/FileDistance.cpp
index 1458146..6bd73e5 100644 (file)
--- a/clang-tools-extra/clangd/FileDistance.cpp
+++ b/clang-tools-extra/clangd/FileDistance.cpp
@@ -196,11 +196,11 @@ static FileDistance createScopeFileDistance(ArrayRef<std::string> QueryScopes) {
     // symbols in it, and there is pattern where using-namespace is used in
     // place of enclosing namespaces (e.g. in implementation files).
     if (S == Preferred)
-      Param.Cost = S == "" ? 2 : 0;
+      Param.Cost = S == "" ? 4 : 0;
     else if (Preferred.startswith(S) && !S.empty())
       continue; // just rely on up-traversals.
     else
-      Param.Cost = S == "" ? 5 : 2;
+      Param.Cost = S == "" ? 6 : 2;
     auto Path = scopeToPath(S);
     // The global namespace is not 'near' its children.
     Param.MaxUpTraversals = std::max(Path.second - 1, 0);