Add an isOne() utility function to ScalarEvolution, similar to isZero()

and similar to ConstantInt's isOne().


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@72003 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 10 insertions, 1 deletions

diff --git a/include/llvm/Analysis/ScalarEvolution.h b/include/llvm/Analysis/ScalarEvolution.h
index 76e23b1169..a5534e89c4 100644
--- a/include/llvm/Analysis/ScalarEvolution.h
+++ b/include/llvm/Analysis/ScalarEvolution.h
@@ -77,6 +77,10 @@ namespace llvm {
     ///
     bool isZero() const;
 
+    /// isOne - Return true if the expression is a constant one.
+    ///
+    bool isOne() const;
+
     /// replaceSymbolicValuesWithConcrete - If this SCEV internally references
     /// the symbolic value "Sym", construct and return a new SCEV that produces
     /// the same value, but which uses the concrete value Conc instead of the
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 77a8070631..4b99a869ff 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -127,6 +127,11 @@ bool SCEV::isZero() const {
   return false;
 }
 
+bool SCEV::isOne() const {
+  if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
+    return SC->getValue()->isOne();
+  return false;
+}
 
 SCEVCouldNotCompute::SCEVCouldNotCompute() : SCEV(scCouldNotCompute) {}
 SCEVCouldNotCompute::~SCEVCouldNotCompute() {}
@@ -3392,7 +3397,7 @@ HowManyLessThans(const SCEV *LHS, const SCEV *RHS,
     const SCEVConstant *CStep = dyn_cast<SCEVConstant>(Step);
     if (!CStep || CStep->isZero())
       return UnknownValue;
-    if (CStep->getValue()->getValue() == 1) {
+    if (CStep->isOne()) {
       // With unit stride, the iteration never steps past the limit value.
     } else if (CStep->getValue()->getValue().isStrictlyPositive()) {
       if (const SCEVConstant *CLimit = dyn_cast<SCEVConstant>(RHS)) {