[InstSimplify] fold min/max with limit constant; NFC

This is already done within InstCombine:
https://alive2.llvm.org/ce/z/MiGE22

...but leaving it out of analysis makes it
harder to avoid infinite loops there.

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 4cb3fdb..42e4433 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4080,6 +4080,22 @@ static Value *simplifySelectWithICmpCond(Value *CondVal, Value *TrueVal,
     std::swap(TrueVal, FalseVal);
   }
 
+  // Check for integer min/max with a limit constant:
+  // X > MIN_INT ? X : MIN_INT --> X
+  // X < MAX_INT ? X : MAX_INT --> X
+  if (TrueVal->getType()->isIntOrIntVectorTy()) {
+    Value *X, *Y;
+    SelectPatternFlavor SPF =
+        matchDecomposedSelectPattern(cast<ICmpInst>(CondVal), TrueVal, FalseVal,
+                                     X, Y).Flavor;
+    if (SelectPatternResult::isMinOrMax(SPF) && Pred == getMinMaxPred(SPF)) {
+      APInt LimitC = getMinMaxLimit(getInverseMinMaxFlavor(SPF),
+                                    X->getType()->getScalarSizeInBits());
+      if (match(Y, m_SpecificInt(LimitC)))
+        return X;
+    }
+  }
+
   if (Pred == ICmpInst::ICMP_EQ && match(CmpRHS, m_Zero())) {
     Value *X;
     const APInt *Y;