[PATCH] D47402: [analyzer] Improve simplifySVal performance further.

[Artem Dergachev via Phabricator via cfe-commits]

NoQ created this revision.
NoQ added reviewers: dcoughlin, xazax.hun, a.sidorin, george.karpenkov, szepet, rnkovacs.
Herald added subscribers: cfe-commits, baloghadamsoftware.

Memoize `SValBuilder::simplifySVal()` so that it didn't try to re-simplify the same symbolic expression in the same program state.

Speeds up the analysis by ~25% on the artificial test in `test/Analysis/hangs.c`.


Repository:
  rC Clang

https://reviews.llvm.org/D47402

Files:
  lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp


Index: lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
===================================================================
--- lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
+++ lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
@@ -1222,6 +1222,12 @@
     ProgramStateRef State;
     SValBuilder &SVB;
 
+    // Cache results for the lifetime of the Simplifier. Results change every
+    // time new constraints are added to the program state, which is the whole
+    // point of simplifying, and for that very reason it's pointless to maintain
+    // the same cache for the duration of the whole analysis.
+    llvm::DenseMap<SymbolRef, SVal> Cached;
+
     static bool isUnchanged(SymbolRef Sym, SVal Val) {
       return Sym == Val.getAsSymbol();
     }
@@ -1242,9 +1248,16 @@
     // start producing them.
 
     SVal VisitSymIntExpr(const SymIntExpr *S) {
+      auto I = Cached.find(S);
+      if (I != Cached.end())
+        return I->second;
+
       SVal LHS = Visit(S->getLHS());
-      if (isUnchanged(S->getLHS(), LHS))
-        return SVB.makeSymbolVal(S);
+      if (isUnchanged(S->getLHS(), LHS)) {
+        SVal V = SVB.makeSymbolVal(S);
+        Cached[S] = V;
+        return V;
+      }
       SVal RHS;
       // By looking at the APSInt in the right-hand side of S, we cannot
       // figure out if it should be treated as a Loc or as a NonLoc.
@@ -1263,15 +1276,27 @@
       } else {
         RHS = SVB.makeIntVal(S->getRHS());
       }
-      return SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType());
+
+      SVal V = SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType());
+      Cached[S] = V;
+      return V;
     }
 
     SVal VisitSymSymExpr(const SymSymExpr *S) {
+      auto I = Cached.find(S);
+      if (I != Cached.end())
+        return I->second;
+
       SVal LHS = Visit(S->getLHS());
       SVal RHS = Visit(S->getRHS());
-      if (isUnchanged(S->getLHS(), LHS) && isUnchanged(S->getRHS(), RHS))
-        return SVB.makeSymbolVal(S);
-      return SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType());
+      if (isUnchanged(S->getLHS(), LHS) && isUnchanged(S->getRHS(), RHS)) {
+        SVal V = SVB.makeSymbolVal(S);
+        Cached[S] = V;
+        return V;
+      }
+      SVal V = SVB.evalBinOp(State, S->getOpcode(), LHS, RHS, S->getType());
+      Cached[S] = V;
+      return V;
     }
 
     SVal VisitSymExpr(SymbolRef S) { return nonloc::SymbolVal(S); }


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