[ValueTracking] Handle shl in isKnownNonEqual()

This handles the pattern X != X << C for non-zero X and C and a
non-overflowing shift. This establishes parity with the corresponing
fold for multiplies.

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 1c3d5df..6f89ba9 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2564,6 +2564,19 @@ static bool isNonEqualMul(const Value *V1, const Value *V2, unsigned Depth,
   return false;
 }
 
+/// Return true if V2 == V1 << C, where V1 is known non-zero, C is not 0 and
+/// the shift is nuw or nsw.
+static bool isNonEqualShl(const Value *V1, const Value *V2, unsigned Depth,
+                          const Query &Q) {
+  if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(V2)) {
+    const APInt *C;
+    return match(OBO, m_Shl(m_Specific(V1), m_APInt(C))) &&
+           (OBO->hasNoUnsignedWrap() || OBO->hasNoSignedWrap()) &&
+           !C->isNullValue() && isKnownNonZero(V1, Depth + 1, Q);
+  }
+  return false;
+}
+
 static bool isNonEqualPHIs(const PHINode *PN1, const PHINode *PN2,
                            unsigned Depth, const Query &Q) {
   // Check two PHIs are in same block.
@@ -2665,6 +2678,9 @@ static bool isKnownNonEqual(const Value *V1, const Value *V2, unsigned Depth,
   if (isNonEqualMul(V1, V2, Depth, Q) || isNonEqualMul(V2, V1, Depth, Q))
     return true;
 
+  if (isNonEqualShl(V1, V2, Depth, Q) || isNonEqualShl(V2, V1, Depth, Q))
+    return true;
+
   if (V1->getType()->isIntOrIntVectorTy()) {
     // Are any known bits in V1 contradictory to known bits in V2? If V1
     // has a known zero where V2 has a known one, they must not be equal.