[llvm-commits] CVS: llvm/lib/Transforms/Scalar/SCCP.cpp

[Chris Lattner]

Changes in directory llvm/lib/Transforms/Scalar:

SCCP.cpp updated: 1.91 -> 1.92

---
Log message:

Do not try to optimize PHI nodes with incredibly high degree.  This reduces SCCP
time from 615s to 1.49s on a large testcase that has a gigantic switch statement
that all of the blocks in the function go to (an intepreter).


---
Diffs of the changes:  (+7 -0)

Index: llvm/lib/Transforms/Scalar/SCCP.cpp
diff -u llvm/lib/Transforms/Scalar/SCCP.cpp:1.91 llvm/lib/Transforms/Scalar/SCCP.cpp:1.92
--- llvm/lib/Transforms/Scalar/SCCP.cpp:1.91	Thu Mar 11 23:52:44 2004
+++ llvm/lib/Transforms/Scalar/SCCP.cpp	Tue Mar 16 13:49:59 2004
@@ -500,6 +500,13 @@
     return;  // Quick exit
   }
 
+  // Super-extra-high-degree PHI nodes are unlikely to ever be marked constant,
+  // and slow us down a lot.  Just mark them overdefined.
+  if (PN.getNumIncomingValues() > 64) {
+    markOverdefined(PNIV, &PN);
+    return;
+  }
+
   // Look at all of the executable operands of the PHI node.  If any of them
   // are overdefined, the PHI becomes overdefined as well.  If they are all
   // constant, and they agree with each other, the PHI becomes the identical