[llvm] r266909 - IR: Use SmallVector instead of std::vector of TrackingMDRef

[Duncan P. N. Exon Smith via llvm-commits]

Author: dexonsmith
Date: Wed Apr 20 15:14:09 2016
New Revision: 266909

URL: http://llvm.org/viewvc/llvm-project?rev=266909&view=rev
Log:
IR: Use SmallVector instead of std::vector of TrackingMDRef

Don't use std::vector<TrackingMDRef>, since (at least in some versions
of libc++) std::vector apparently copies values on grow operations
instead of moving them.  Found this when I was temporarily deleting the
copy constructor for TrackingMDRef to investigate a performance
bottleneck.

Modified:
    llvm/trunk/include/llvm/IR/DIBuilder.h
    llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp
    llvm/trunk/lib/IR/DIBuilder.cpp

Modified: llvm/trunk/include/llvm/IR/DIBuilder.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/DIBuilder.h?rev=266909&r1=266908&r2=266909&view=diff
==============================================================================
--- llvm/trunk/include/llvm/IR/DIBuilder.h (original)
+++ llvm/trunk/include/llvm/IR/DIBuilder.h Wed Apr 20 15:14:09 2016
@@ -51,7 +51,11 @@ namespace llvm {
     bool AllowUnresolvedNodes;
 
     /// Each subprogram's preserved local variables.
-    DenseMap<MDNode *, std::vector<TrackingMDNodeRef>> PreservedVariables;
+    ///
+    /// Do not use a std::vector.  Some versions of libc++ apparently copy
+    /// instead of move on grow operations, and TrackingMDRef is expensive to
+    /// copy.
+    DenseMap<MDNode *, SmallVector<TrackingMDNodeRef, 1>> PreservedVariables;
 
     DIBuilder(const DIBuilder &) = delete;
     void operator=(const DIBuilder &) = delete;

Modified: llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp?rev=266909&r1=266908&r2=266909&view=diff
==============================================================================
--- llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp (original)
+++ llvm/trunk/lib/Bitcode/Reader/BitcodeReader.cpp Wed Apr 20 15:14:09 2016
@@ -107,7 +107,12 @@ class BitcodeReaderMetadataList {
   bool AnyFwdRefs;
   unsigned MinFwdRef;
   unsigned MaxFwdRef;
-  std::vector<TrackingMDRef> MetadataPtrs;
+
+  /// Array of metadata references.
+  ///
+  /// Don't use std::vector here.  Some versions of libc++ copy (instead of
+  /// move) on resize, and TrackingMDRef is very expensive to copy.
+  SmallVector<TrackingMDRef, 1> MetadataPtrs;
 
   LLVMContext &Context;
 public:

Modified: llvm/trunk/lib/IR/DIBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/DIBuilder.cpp?rev=266909&r1=266908&r2=266909&view=diff
==============================================================================
--- llvm/trunk/lib/IR/DIBuilder.cpp (original)
+++ llvm/trunk/lib/IR/DIBuilder.cpp Wed Apr 20 15:14:09 2016
@@ -614,7 +614,7 @@ DIGlobalVariable *DIBuilder::createTempG
 
 static DILocalVariable *createLocalVariable(
     LLVMContext &VMContext,
-    DenseMap<MDNode *, std::vector<TrackingMDNodeRef>> &PreservedVariables,
+    DenseMap<MDNode *, SmallVector<TrackingMDNodeRef, 1>> &PreservedVariables,
     DIScope *Scope, StringRef Name, unsigned ArgNo, DIFile *File,
     unsigned LineNo, DIType *Ty, bool AlwaysPreserve, unsigned Flags) {
   // FIXME: Why getNonCompileUnitScope()?