[IR] CmpInst: add getUnsignedPredicate()

There's already getSignedPredicate(), it is not symmetrical to not have
it's opposite. I wanted to use it in new code, but it wasn't there..

llvm/include/llvm/IR/InstrTypes.h

@@ -920,6 +920,18 @@ public:
     return getSignedPredicate(getPredicate());
   }
 
+  /// For example, SLT->ULT, SLE->ULE, SGT->UGT, SGE->UGE, ULT->Failed assert
+  /// @returns the unsigned version of the signed predicate pred.
+  static Predicate getUnsignedPredicate(Predicate pred);
+
+  /// For example, SLT->ULT, SLE->ULE, SGT->UGT, SGE->UGE, ULT->Failed assert
+  /// @returns the unsigned version of the predicate for this instruction (which
+  /// has to be an signed predicate).
+  /// return the unsigned version of a predicate
+  Predicate getUnsignedPredicate() {
+    return getUnsignedPredicate(getPredicate());
+  }
+
   /// This is just a convenience.
   /// Determine if this is true when both operands are the same.
   bool isTrueWhenEqual() const {

llvm/lib/IR/Instructions.cpp

@@ -3847,7 +3847,7 @@ CmpInst::Predicate CmpInst::getNonStrictPredicate(Predicate pred) {
 }
 
 CmpInst::Predicate CmpInst::getSignedPredicate(Predicate pred) {
-  assert(CmpInst::isUnsigned(pred) && "Call only with signed predicates!");
+  assert(CmpInst::isUnsigned(pred) && "Call only with unsigned predicates!");
 
   switch (pred) {
   default:
@@ -3863,6 +3863,23 @@ CmpInst::Predicate CmpInst::getSignedPredicate(Predicate pred) {
   }
 }
 
+CmpInst::Predicate CmpInst::getUnsignedPredicate(Predicate pred) {
+  assert(CmpInst::isSigned(pred) && "Call only with signed predicates!");
+
+  switch (pred) {
+  default:
+    llvm_unreachable("Unknown predicate!");
+  case CmpInst::ICMP_SLT:
+    return CmpInst::ICMP_ULT;
+  case CmpInst::ICMP_SLE:
+    return CmpInst::ICMP_ULE;
+  case CmpInst::ICMP_SGT:
+    return CmpInst::ICMP_UGT;
+  case CmpInst::ICMP_SGE:
+    return CmpInst::ICMP_UGE;
+  }
+}
+
 bool CmpInst::isUnsigned(Predicate predicate) {
   switch (predicate) {
     default: return false;