[ValueTracking] Add logic for `isKnownNonZero(smin/smax X, Y)`

For `smin` if either `X` or `Y` is negative, the result is non-zero.
For `smax` if either `X` or `Y` is strictly positive, the result is
non-zero.

For both if `X != 0` and `Y != 0` the result is non-zero.

Alive2 Link:
    https://alive2.llvm.org/ce/z/7yvbgN
    https://alive2.llvm.org/ce/z/zizbvq

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D149417

1 files changed, 20 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 8551de6..fa267ce 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2942,6 +2942,26 @@ bool isKnownNonZero(const Value *V, const APInt &DemandedElts, unsigned Depth,
             isKnownNonZero(II->getArgOperand(1), DemandedElts, Depth, Q))
           return true;
         break;
+      case Intrinsic::smin:
+      case Intrinsic::smax: {
+        auto KnownOpImpliesNonZero = [&](const KnownBits &K) {
+          return II->getIntrinsicID() == Intrinsic::smin
+                     ? K.isNegative()
+                     : K.isStrictlyPositive();
+        };
+        KnownBits XKnown =
+            computeKnownBits(II->getArgOperand(0), DemandedElts, Depth, Q);
+        if (KnownOpImpliesNonZero(XKnown))
+          return true;
+        KnownBits YKnown =
+            computeKnownBits(II->getArgOperand(1), DemandedElts, Depth, Q);
+        if (KnownOpImpliesNonZero(YKnown))
+          return true;
+
+        if (XKnown.isNonZero() && YKnown.isNonZero())
+          return true;
+      }
+        [[fallthrough]];
       case Intrinsic::umin:
         return isKnownNonZero(II->getArgOperand(0), DemandedElts, Depth, Q) &&
                isKnownNonZero(II->getArgOperand(1), DemandedElts, Depth, Q);