[OpenMP] set_bits iterator yields unsigned elements, no reference (NFC).

[fhahn]

Summary

BitVector::set_bits() returns an iterator range yielding unsinged
elements, which always will be copied while const & gives the impression
that there will be no copy. Newer version of clang complain:

warning: loop variable 'SetBitsIt' is always a copy because the range of type 'iterator_range<llvm::BitVector::const_set_bits_iterator>' (aka 'iterator_range<const_set_bits_iterator_impl<llvm::BitVector> >') does not return a reference [-Wrange-loop-analysis]

[rnk]

Lgtm, thanks, I was seeing this locally

llvm/lib/Frontend/OpenMP/OMPContext.cpp

#include "llvm/Frontend/OpenMP/OMPKinds.def"
   ActiveTraits.set(unsigned(TraitProperty::user_condition_true));
 
   // This is for sure some device.
   ActiveTraits.set(unsigned(TraitProperty::device_kind_any));
 
   LLVM_DEBUG({
     dbgs() << "[" << DEBUG_TYPE
            << "] New OpenMP context with the following properties:\n";
-    for (const auto &SetBitsIt : ActiveTraits.set_bits()) {
-      TraitProperty Property = TraitProperty(SetBitsIt);
+    for (unsigned Bit : ActiveTraits.set_bits()) {
+      TraitProperty Property = TraitProperty(Bit);
       dbgs() << "\t " << getOpenMPContextTraitPropertyFullName(Property)
              << "\n";
     }
   });
 }
 
 /// Return true if \p C0 is a subset of \p C1. Note that both arrays are
 /// expected to be sorted.

 
 static bool isStrictSubset(const VariantMatchInfo &VMI0,
                            const VariantMatchInfo &VMI1) {
   // If all required traits are a strict subset and the ordered vectors storing
   // the construct traits, we say it is a strict subset. Note that the latter
   // relation is not required to be strict.
   if (VMI0.RequiredTraits.count() >= VMI1.RequiredTraits.count())
     return false;
-  for (const auto &SetBitsIt : VMI0.RequiredTraits.set_bits())
-    if (!VMI1.RequiredTraits.test(SetBitsIt))
+  for (unsigned Bit : VMI0.RequiredTraits.set_bits())
+    if (!VMI1.RequiredTraits.test(Bit))
       return false;
   if (!isSubset<TraitProperty>(VMI0.ConstructTraits, VMI1.ConstructTraits))
     return false;
   return true;
 }
 
 static int isVariantApplicableInContextHelper(
     const VariantMatchInfo &VMI, const OMPContext &Ctx,
     SmallVectorImpl<unsigned> *ConstructMatches) {
 
-  for (const auto &SetBitsIt : VMI.RequiredTraits.set_bits()) {
-    TraitProperty Property = TraitProperty(SetBitsIt);
+  for (unsigned Bit : VMI.RequiredTraits.set_bits()) {
+    TraitProperty Property = TraitProperty(Bit);
 
     bool IsActiveTrait = Ctx.ActiveTraits.test(unsigned(Property));
     if (!IsActiveTrait) {
       LLVM_DEBUG(dbgs() << "[" << DEBUG_TYPE << "] Property "
                         << getOpenMPContextTraitPropertyName(Property)
                         << " was not in the OpenMP context.\n");
       return false;
     }

 }
 
 static APInt getVariantMatchScore(const VariantMatchInfo &VMI,
                                   const OMPContext &Ctx,
                                   SmallVectorImpl<unsigned> &ConstructMatches) {
   APInt Score(64, 1);
 
   unsigned NoConstructTraits = VMI.ConstructTraits.size();
-  for (const auto &SetBitsIt : VMI.RequiredTraits.set_bits()) {
-    TraitProperty Property = TraitProperty(SetBitsIt);
+  for (unsigned Bit : VMI.RequiredTraits.set_bits()) {
+    TraitProperty Property = TraitProperty(Bit);
     // If there is a user score attached, use it.
     if (VMI.ScoreMap.count(Property)) {
       const APInt &UserScore = VMI.ScoreMap.lookup(Property);
       assert(UserScore.uge(0) && "Expect non-negative user scores!");
       Score += UserScore.getZExtValue();
       continue;
     }