[NFC] Detect IV increment expressed as uadd_with_overflow and usub_with_overflow

Current callers do not call it with such argument, so this is NFC.
But for further changes, it can be very useful to detect such cases.

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 2c2f667..d87d500 100644 (file)
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -1293,6 +1293,12 @@ getIVIncrement(const PHINode *PN, const LoopInfo *LI) {
     return std::make_pair(IVInc, ConstantExpr::getNeg(Step));
   if (match(IVInc, m_Add(m_Specific(PN), m_Constant(Step))))
     return std::make_pair(IVInc, Step);
+  if (match(IVInc, m_ExtractValue<0>(m_Intrinsic<Intrinsic::usub_with_overflow>(
+                       m_Specific(PN), m_Constant(Step)))))
+    return std::make_pair(IVInc, ConstantExpr::getNeg(Step));
+  if (match(IVInc, m_ExtractValue<0>(m_Intrinsic<Intrinsic::uadd_with_overflow>(
+                       m_Specific(PN), m_Constant(Step)))))
+    return std::make_pair(IVInc, Step);
   return None;
 }