[llvm] r208237 - do not collect undef terms

[Sebastian Pop]

Author: spop
Date: Wed May  7 14:00:32 2014
New Revision: 208237

URL: http://llvm.org/viewvc/llvm-project?rev=208237&view=rev
Log:
do not collect undef terms

Modified:
    llvm/trunk/lib/Analysis/ScalarEvolution.cpp

Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=208237&r1=208236&r2=208237&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Wed May  7 14:00:32 2014
@@ -6816,6 +6816,40 @@ const SCEV *SCEVAddRecExpr::getNumIterat
 }
 
 namespace {
+struct FindUndefs {
+  bool Found;
+  FindUndefs() : Found(false) {}
+
+  bool follow(const SCEV *S) {
+    if (const SCEVUnknown *C = dyn_cast<SCEVUnknown>(S)) {
+      if (isa<UndefValue>(C->getValue()))
+        Found = true;
+    } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
+      if (isa<UndefValue>(C->getValue()))
+        Found = true;
+    }
+
+    // Keep looking if we haven't found it yet.
+    return !Found;
+  }
+  bool isDone() const {
+    // Stop recursion if we have found an undef.
+    return Found;
+  }
+};
+}
+
+// Return true when S contains at least an undef value.
+static inline bool
+containsUndefs(const SCEV *S) {
+  FindUndefs F;
+  SCEVTraversal<FindUndefs> ST(F);
+  ST.visitAll(S);
+
+  return F.Found;
+}
+
+namespace {
 // Collect all steps of SCEV expressions.
 struct SCEVCollectStrides {
   ScalarEvolution &SE;
@@ -6841,7 +6875,8 @@ struct SCEVCollectTerms {
 
   bool follow(const SCEV *S) {
     if (isa<SCEVUnknown>(S) || isa<SCEVConstant>(S) || isa<SCEVMulExpr>(S)) {
-      Terms.push_back(S);
+      if (!containsUndefs(S))
+        Terms.push_back(S);
 
       // Stop recursion: once we collected a term, do not walk its operands.
       return false;