From: Nikita Popov <nikita.ppv@gmail.com>
Date: Sat, 12 Jan 2019 09:09:15 +0000 (+0000)
Subject: Reapply "[DemandedBits] Use SetVector for Worklist"
X-Git-Tag: llvmorg-8.0.0-rc1~358
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=5f393eb5da7f749e651ae9181515fa16554ebcbe;p=platform%2Fupstream%2Fllvm.git

Reapply "[DemandedBits] Use SetVector for Worklist"

DemandedBits currently uses a simple vector for the worklist, which
means that instructions may be inserted multiple times into it.
Especially in combination with the deep lattice, this may cause
instructions too be recomputed very often. To avoid this, switch
to a SetVector.

Reapplying with a smaller number of inline elements in the
SmallSetVector, to avoid running into the SmallDenseMap issue
described in D56455.

Differential Revision: https://reviews.llvm.org/D56362

llvm-svn: 350997
---

diff --git a/llvm/lib/Analysis/DemandedBits.cpp b/llvm/lib/Analysis/DemandedBits.cpp
index ba310d8..34f785fb 100644
--- a/llvm/lib/Analysis/DemandedBits.cpp
+++ b/llvm/lib/Analysis/DemandedBits.cpp
@@ -21,8 +21,7 @@
 
 #include "llvm/Analysis/DemandedBits.h"
 #include "llvm/ADT/APInt.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/ValueTracking.h"
@@ -315,7 +314,7 @@ void DemandedBits::performAnalysis() {
   AliveBits.clear();
   DeadUses.clear();
 
-  SmallVector<Instruction*, 128> Worklist;
+  SmallSetVector<Instruction*, 16> Worklist;
 
   // Collect the set of "root" instructions that are known live.
   for (Instruction &I : instructions(F)) {
@@ -330,7 +329,7 @@ void DemandedBits::performAnalysis() {
     Type *T = I.getType();
     if (T->isIntOrIntVectorTy()) {
       if (AliveBits.try_emplace(&I, T->getScalarSizeInBits(), 0).second)
-        Worklist.push_back(&I);
+        Worklist.insert(&I);
 
       continue;
     }
@@ -341,7 +340,7 @@ void DemandedBits::performAnalysis() {
         Type *T = J->getType();
         if (T->isIntOrIntVectorTy())
           AliveBits[J] = APInt::getAllOnesValue(T->getScalarSizeInBits());
-        Worklist.push_back(J);
+        Worklist.insert(J);
       }
     }
     // To save memory, we don't add I to the Visited set here. Instead, we
@@ -412,11 +411,11 @@ void DemandedBits::performAnalysis() {
           APInt ABNew = AB | ABPrev;
           if (ABNew != ABPrev || ABI == AliveBits.end()) {
             AliveBits[I] = std::move(ABNew);
-            Worklist.push_back(I);
+            Worklist.insert(I);
           }
         }
       } else if (I && !Visited.count(I)) {
-        Worklist.push_back(I);
+        Worklist.insert(I);
       }
     }
   }