Add new SCEV, SCEVSMax. This allows LLVM to analyze do-while loops.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44319 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 31 insertions, 2 deletions

diff --git a/include/llvm/Analysis/ScalarEvolution.h b/include/llvm/Analysis/ScalarEvolution.h
index a52f273..d0886e8 100644
--- a/include/llvm/Analysis/ScalarEvolution.h
+++ b/include/llvm/Analysis/ScalarEvolution.h
@@ -235,6 +235,8 @@ namespace llvm {
       std::vector<SCEVHandle> NewOp(Operands);
       return getAddRecExpr(NewOp, L);
     }
+    SCEVHandle getSMaxExpr(const SCEVHandle &LHS, const SCEVHandle &RHS);
+    SCEVHandle getSMaxExpr(std::vector<SCEVHandle> Operands);
     SCEVHandle getUnknown(Value *V);
 
     /// getNegativeSCEV - Return the SCEV object corresponding to -V.
diff --git a/include/llvm/Analysis/ScalarEvolutionExpander.h b/include/llvm/Analysis/ScalarEvolutionExpander.h
index 8582067..6529902 100644
--- a/include/llvm/Analysis/ScalarEvolutionExpander.h
+++ b/include/llvm/Analysis/ScalarEvolutionExpander.h
@@ -134,6 +134,8 @@ namespace llvm {
 
     Value *visitAddRecExpr(SCEVAddRecExpr *S);
 
+    Value *visitSMaxExpr(SCEVSMaxExpr *S);
+
     Value *visitUnknown(SCEVUnknown *S) {
       return S->getValue();
     }
diff --git a/include/llvm/Analysis/ScalarEvolutionExpressions.h b/include/llvm/Analysis/ScalarEvolutionExpressions.h
index fb69a90..f639243 100644
--- a/include/llvm/Analysis/ScalarEvolutionExpressions.h
+++ b/include/llvm/Analysis/ScalarEvolutionExpressions.h
@@ -25,7 +25,7 @@ namespace llvm {
     // These should be ordered in terms of increasing complexity to make the
     // folders simpler.
     scConstant, scTruncate, scZeroExtend, scSignExtend, scAddExpr, scMulExpr,
-    scSDivExpr, scAddRecExpr, scUnknown, scCouldNotCompute
+    scSDivExpr, scAddRecExpr, scSMaxExpr, scUnknown, scCouldNotCompute
   };
 
   //===--------------------------------------------------------------------===//
@@ -274,7 +274,8 @@ namespace llvm {
     static inline bool classof(const SCEVCommutativeExpr *S) { return true; }
     static inline bool classof(const SCEV *S) {
       return S->getSCEVType() == scAddExpr ||
-             S->getSCEVType() == scMulExpr;
+             S->getSCEVType() == scMulExpr ||
+             S->getSCEVType() == scSMaxExpr;
     }
   };
 
@@ -459,6 +460,28 @@ namespace llvm {
     }
   };
 
+
+  //===--------------------------------------------------------------------===//
+  /// SCEVSMaxExpr - This class represents a signed maximum selection.
+  ///
+  class SCEVSMaxExpr : public SCEVCommutativeExpr {
+    friend class ScalarEvolution;
+
+    explicit SCEVSMaxExpr(const std::vector<SCEVHandle> &ops)
+      : SCEVCommutativeExpr(scSMaxExpr, ops) {
+    }
+
+  public:
+    virtual const char *getOperationStr() const { return " smax "; }
+
+    /// Methods for support type inquiry through isa, cast, and dyn_cast:
+    static inline bool classof(const SCEVSMaxExpr *S) { return true; }
+    static inline bool classof(const SCEV *S) {
+      return S->getSCEVType() == scSMaxExpr;
+    }
+  };
+
+
   //===--------------------------------------------------------------------===//
   /// SCEVUnknown - This means that we are dealing with an entirely unknown SCEV
   /// value, and only represent it as it's LLVM Value.  This is the "bottom"
@@ -521,6 +544,8 @@ namespace llvm {
         return ((SC*)this)->visitSDivExpr((SCEVSDivExpr*)S);
       case scAddRecExpr:
         return ((SC*)this)->visitAddRecExpr((SCEVAddRecExpr*)S);
+      case scSMaxExpr:
+        return ((SC*)this)->visitSMaxExpr((SCEVSMaxExpr*)S);
       case scUnknown:
         return ((SC*)this)->visitUnknown((SCEVUnknown*)S);
       case scCouldNotCompute: