[ConstantRange] Generalize makeGuaranteedNoWrapRegion to work on ranges

This will be used in a later patch to ScalarEvolution.  Right now only
the unit tests exercise the newly added code.

llvm-svn: 262637

1 files changed, 20 insertions, 12 deletions

diff --git a/llvm/lib/IR/ConstantRange.cpp b/llvm/lib/IR/ConstantRange.cpp
index 521511ade5c..417b752d1a2 100644
--- a/llvm/lib/IR/ConstantRange.cpp
+++ b/llvm/lib/IR/ConstantRange.cpp
@@ -129,7 +129,8 @@ ConstantRange ConstantRange::makeSatisfyingICmpRegion(CmpInst::Predicate Pred,
 
 ConstantRange
 ConstantRange::makeGuaranteedNoWrapRegion(Instruction::BinaryOps BinOp,
-                                          const APInt &C, unsigned NoWrapKind) {
+                                          const ConstantRange &Other,
+                                          unsigned NoWrapKind) {
   typedef OverflowingBinaryOperator OBO;
 
   // Computes the intersection of CR0 and CR1.  It is different from
@@ -149,29 +150,36 @@ ConstantRange::makeGuaranteedNoWrapRegion(Instruction::BinaryOps BinOp,
           NoWrapKind == (OBO::NoUnsignedWrap | OBO::NoSignedWrap)) &&
          "NoWrapKind invalid!");
 
-  unsigned BitWidth = C.getBitWidth();
+  unsigned BitWidth = Other.getBitWidth();
   if (BinOp != Instruction::Add)
     // Conservative answer: empty set
     return ConstantRange(BitWidth, false);
 
-  if (C.isMinValue())
-    // Full set: nothing signed / unsigned wraps when added to 0.
-    return ConstantRange(BitWidth);
+  if (auto *C = Other.getSingleElement())
+    if (C->isMinValue())
+      // Full set: nothing signed / unsigned wraps when added to 0.
+      return ConstantRange(BitWidth);
 
   ConstantRange Result(BitWidth);
 
   if (NoWrapKind & OBO::NoUnsignedWrap)
-    Result = SubsetIntersect(Result,
-                             ConstantRange(APInt::getNullValue(BitWidth), -C));
+    Result =
+        SubsetIntersect(Result, ConstantRange(APInt::getNullValue(BitWidth),
+                                              -Other.getUnsignedMax()));
 
   if (NoWrapKind & OBO::NoSignedWrap) {
-    if (C.isStrictlyPositive())
+    APInt SignedMin = Other.getSignedMin();
+    APInt SignedMax = Other.getSignedMax();
+
+    if (SignedMax.isStrictlyPositive())
       Result = SubsetIntersect(
-          Result, ConstantRange(APInt::getSignedMinValue(BitWidth),
-                                APInt::getSignedMinValue(BitWidth) - C));
-    else
+          Result,
+          ConstantRange(APInt::getSignedMinValue(BitWidth),
+                        APInt::getSignedMinValue(BitWidth) - SignedMax));
+
+    if (SignedMin.isNegative())
       Result = SubsetIntersect(
-          Result, ConstantRange(APInt::getSignedMinValue(BitWidth) - C,
+          Result, ConstantRange(APInt::getSignedMinValue(BitWidth) - SignedMin,
                                 APInt::getSignedMinValue(BitWidth)));
   }