[llvm] r258297 - [Verifier] Fix performance regression for LTO builds

[Ivan Krasin via llvm-commits]

Author: krasin
Date: Wed Jan 20 02:41:22 2016
New Revision: 258297

URL: http://llvm.org/viewvc/llvm-project?rev=258297&view=rev
Log:
[Verifier] Fix performance regression for LTO builds

Summary:
Fix a significant performance regression by introducing GlobalValueVisited field and reusing the map.
This is a follow up to r257823 that slowed down linking Chrome with LTO by 2.5x.

If you revert this commit, please, also revert r257823.

BUG=https://llvm.org/bugs/show_bug.cgi?id=26214

Reviewers: pcc, loladiro, joker.eph

Subscribers: krasin1, joker.eph, loladiro, pcc

Differential Revision: http://reviews.llvm.org/D16338

Modified:
    llvm/trunk/lib/IR/Verifier.cpp

Modified: llvm/trunk/lib/IR/Verifier.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Verifier.cpp?rev=258297&r1=258296&r2=258297&view=diff
==============================================================================
--- llvm/trunk/lib/IR/Verifier.cpp (original)
+++ llvm/trunk/lib/IR/Verifier.cpp Wed Jan 20 02:41:22 2016
@@ -217,6 +217,12 @@ class Verifier : public InstVisitor<Veri
   /// Cache of constants visited in search of ConstantExprs.
   SmallPtrSet<const Constant *, 32> ConstantExprVisited;
 
+  // Verify that this GlobalValue is only used in this module.
+  // This map is used to avoid visiting uses twice. We can arrive at a user
+  // twice, if they have multiple operands. In particular for very large
+  // constant expressions, we can arrive at a particular user many times.
+  SmallPtrSet<const Value *, 32> GlobalValueVisited;
+
   void checkAtomicMemAccessSize(const Module *M, Type *Ty,
                                 const Instruction *I);
 public:
@@ -494,12 +500,7 @@ void Verifier::visitGlobalValue(const Gl
   if (GV.isDeclarationForLinker())
     Assert(!GV.hasComdat(), "Declaration may not be in a Comdat!", &GV);
 
-  // Verify that this GlobalValue is only used in this module.
-  // This map is used to avoid visiting uses twice. We can arrive at a user
-  // twice, if they have multiple operands. In particular for very large
-  // constant expressions, we can arrive at a particular user many times.
-  SmallPtrSet<const Value *, 32> Visited;
-  forEachUser(&GV, Visited, [&](const Value *V) -> bool {
+  forEachUser(&GV, GlobalValueVisited, [&](const Value *V) -> bool {
     if (const Instruction *I = dyn_cast<Instruction>(V)) {
       if (!I->getParent() || !I->getParent()->getParent())
         CheckFailed("Global is referenced by parentless instruction!", &GV,