[SCEV] Add smin support to getRangeRef

We were failing to compute trip counts (both exact and maximum) for any loop which involved a comparison against either an umin or smin. It looks like this simply got missed when we added smin/umin to SCEV.  (Note: umin was submitted separately earlier today.  Turned out two folks hit this at the same time.)

Differential Revision: https://reviews.llvm.org/D67514

llvm-svn: 371776

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 3817b1142d3..2cac4a090ff 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -5596,6 +5596,14 @@ ScalarEvolution::getRangeRef(const SCEV *S,
                     ConservativeResult.intersectWith(X, RangeType));
   }
 
+  if (const SCEVSMinExpr *SMin = dyn_cast<SCEVSMinExpr>(S)) {
+    ConstantRange X = getRangeRef(SMin->getOperand(0), SignHint);
+    for (unsigned i = 1, e = SMin->getNumOperands(); i != e; ++i)
+      X = X.smin(getRangeRef(SMin->getOperand(i), SignHint));
+    return setRange(SMin, SignHint,
+                    ConservativeResult.intersectWith(X, RangeType));
+  }
+
   if (const SCEVUMinExpr *UMin = dyn_cast<SCEVUMinExpr>(S)) {
     ConstantRange X = getRangeRef(UMin->getOperand(0), SignHint);
     for (unsigned i = 1, e = UMin->getNumOperands(); i != e; ++i)