Amend r138129 (reduction of SLocEntries) which introduced performance regression due

to increased calls to SourceManager::getFileID. (rdar://9992664)

Use a slightly different approach that is more efficient both in terms of speed
(no extra getFileID calls) and in SLocEntries reduction.

Comparing pre-r138129 and this patch we get:

For compiling SemaExpr.cpp reduction of SLocEntries by 26%.
For the boost enum library:
  -SLocEntries -34% (note that this was -5% for r138129)
  -Memory consumption -50%
  -PCH size -31%

Reduced SLocEntries also benefit the hot function SourceManager::getFileID,
evident by the reduced "FileID scans".

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@138380 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 19 insertions, 0 deletions

diff --git a/include/clang/Basic/SourceManager.h b/include/clang/Basic/SourceManager.h
index 8799106a03..79eba4f353 100644
--- a/include/clang/Basic/SourceManager.h
+++ b/include/clang/Basic/SourceManager.h
@@ -906,6 +906,25 @@ public:
     return false;
   }
 
+  /// \brief Return true if both \arg LHS and \arg RHS are in the local source
+  /// location address space or the loaded one. If it's true and
+  /// \arg RelativeOffset is non-null, it will be set to the offset of \arg RHS
+  /// relative to \arg LHS.
+  bool isInSameSLocAddrSpace(SourceLocation LHS, SourceLocation RHS,
+                             int *RelativeOffset) const {
+    unsigned LHSOffs = LHS.getOffset(), RHSOffs = RHS.getOffset();
+    bool LHSLoaded = LHSOffs >= CurrentLoadedOffset;
+    bool RHSLoaded = RHSOffs >= CurrentLoadedOffset;
+
+    if (LHSLoaded == RHSLoaded) {
+      if (RelativeOffset)
+        *RelativeOffset = RHSOffs - LHSOffs;
+      return true;
+    }
+
+    return false;
+  }
+
   //===--------------------------------------------------------------------===//
   // Queries about the code at a SourceLocation.
   //===--------------------------------------------------------------------===//