Step #3 to improving trip count analysis: If we fold

a + {b,+,stride} into {a+b,+,stride}  (because a is LIV),
then the resultant AddRec is NUW/NSW if the client says it
is.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123133 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index d3d65847cbca195c4f2cc5380e68166e1155504d..89daec8053e4df9fa6ca91e2af28443f03bc16f5 100644 (file)
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -1560,10 +1560,14 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
       AddRecOps[0] = getAddExpr(LIOps);
 
       // Build the new addrec. Propagate the NUW and NSW flags if both the
-      // outer add and the inner addrec are guaranteed to have no overflow.
-      const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop,
-                                         HasNUW && AddRec->hasNoUnsignedWrap(),
-                                         HasNSW && AddRec->hasNoSignedWrap());
+      // outer add and the inner addrec are guaranteed to have no overflow or if
+      // there is no outer part.
+      if (Ops.size() != 1) {
+        HasNUW &= AddRec->hasNoUnsignedWrap();
+        HasNSW &= AddRec->hasNoSignedWrap();
+      }
+      
+      const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop, HasNUW, HasNSW);
 
       // If all of the other operands were loop invariant, we are done.
       if (Ops.size() == 1) return NewRec;