[PATCH] D80428: [clang] Optimize getFileIDLocal

[Marco Elver via Phabricator via cfe-commits]

melver created this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

- Avoid bit operations to compute Offset by removing bitfields. On 64-bit architectures, SLocEntry's size is unchanged.

- Provide branch-prediction hints to compiler to generate better code.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D80428

Files:
  clang/include/clang/Basic/SourceManager.h
  clang/lib/Basic/SourceManager.cpp


Index: clang/lib/Basic/SourceManager.cpp
===================================================================
--- clang/lib/Basic/SourceManager.cpp
+++ clang/lib/Basic/SourceManager.cpp
@@ -885,14 +885,14 @@
     bool Invalid = false;
     unsigned MiddleIndex = (GreaterIndex-LessIndex)/2+LessIndex;
     unsigned MidOffset = getLocalSLocEntry(MiddleIndex, &Invalid).getOffset();
-    if (Invalid)
+    if (LLVM_UNLIKELY(Invalid))
       return FileID::get(0);
 
     ++NumProbes;
 
     // If the offset of the midpoint is too large, chop the high side of the
     // range to the midpoint.
-    if (MidOffset > SLocOffset) {
+    if (LLVM_LIKELY(MidOffset > SLocOffset)) {
       GreaterIndex = MiddleIndex;
       continue;
     }
Index: clang/include/clang/Basic/SourceManager.h
===================================================================
--- clang/include/clang/Basic/SourceManager.h
+++ clang/include/clang/Basic/SourceManager.h
@@ -439,8 +439,8 @@
   /// SourceManager keeps an array of these objects, and they are uniquely
   /// identified by the FileID datatype.
   class SLocEntry {
-    unsigned Offset : 31;
-    unsigned IsExpansion : 1;
+    unsigned Offset;
+    bool IsExpansion;
     union {
       FileInfo File;
       ExpansionInfo Expansion;
@@ -465,7 +465,6 @@
     }
 
     static SLocEntry get(unsigned Offset, const FileInfo &FI) {
-      assert(!(Offset & (1u << 31)) && "Offset is too large");
       SLocEntry E;
       E.Offset = Offset;
       E.IsExpansion = false;
@@ -474,7 +473,6 @@
     }
 
     static SLocEntry get(unsigned Offset, const ExpansionInfo &Expansion) {
-      assert(!(Offset & (1u << 31)) && "Offset is too large");
       SLocEntry E;
       E.Offset = Offset;
       E.IsExpansion = true;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D80428.265700.patch
Type: text/x-patch
Size: 1751 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20200522/df67bac7/attachment-0001.bin>