[llvm-commits] [llvm] r120457 - /llvm/trunk/lib/Transforms/Scalar/SCCP.cpp

[Dale Johannesen]

Author: johannes
Date: Tue Nov 30 14:23:21 2010
New Revision: 120457

URL: http://llvm.org/viewvc/llvm-project?rev=120457&view=rev
Log:
Avoid exponential growth of a table.  It feels like
there should be a better way to do this.  PR 8679.


Modified:
    llvm/trunk/lib/Transforms/Scalar/SCCP.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/SCCP.cpp?rev=120457&r1=120456&r2=120457&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/SCCP.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/SCCP.cpp Tue Nov 30 14:23:21 2010
@@ -481,6 +481,23 @@
     }
   }
 
+  /// InsertInOverdefinedPHIs - Insert an entry in the UsersOfOverdefinedPHIS
+  /// map for I and PN, but if one is there already, do not create another.
+  /// (Duplicate entries do not break anything directly, but can lead to
+  /// exponential growth of the table in rare cases.)
+  void InsertInOverdefinedPHIs(Instruction *I, PHINode *PN) {
+    std::multimap<PHINode*, Instruction*>::iterator J, E;
+    bool found = false;
+    tie(J, E) = UsersOfOverdefinedPHIs.equal_range(PN);
+    for (; J != E; ++J)
+      if (J->second == I) {
+        found = true;
+        break;
+      }
+    if (!found)
+      UsersOfOverdefinedPHIs.insert(std::make_pair(PN, I));
+  }
+
 private:
   friend class InstVisitor<SCCPSolver>;
 
@@ -973,9 +990,9 @@
         if (Result.isConstant()) {
           markConstant(IV, &I, Result.getConstant());
           // Remember that this instruction is virtually using the PHI node
-          // operands.
-          UsersOfOverdefinedPHIs.insert(std::make_pair(PN1, &I));
-          UsersOfOverdefinedPHIs.insert(std::make_pair(PN2, &I));
+          // operands. 
+          InsertInOverdefinedPHIs(&I, PN1);
+          InsertInOverdefinedPHIs(&I, PN2);
           return;
         }
         
@@ -1056,8 +1073,8 @@
           markConstant(&I, Result.getConstant());
           // Remember that this instruction is virtually using the PHI node
           // operands.
-          UsersOfOverdefinedPHIs.insert(std::make_pair(PN1, &I));
-          UsersOfOverdefinedPHIs.insert(std::make_pair(PN2, &I));
+          InsertInOverdefinedPHIs(&I, PN1);
+          InsertInOverdefinedPHIs(&I, PN2);
           return;
         }