Improve BitVecOps<>::Iter::NextElem (#11696)

* Improve BitVecOps<>::Iter::NextElem

Tweak the implementation, to reduce the number of instructions
executed in the hot path.

Also, don't pass "env" to NextElem; it can be stored by Init()
if required. For non-inlined calls, this saves setting up one
argument.

Use a `m_bsEnd` end condition. This eliminates the need to handle
short/long differently, and reduces conditions when updating
the current bits to iterate over in the long case.

Overall, pin shows this reduces instruction count of superpmi over
a minopts test run by 2.6% (NextElem is very hot).

Also, fix BitSetAsUInt64 NextElem() iterator: It should store and updated
its own bit count, and not depend on the value passed in to be the
correct latest bit count.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/jit/rangecheck.cpp b/src/jit/rangecheck.cpp
index 91ae81e322..403113255b 100644
--- a/src/jit/rangecheck.cpp
+++ b/src/jit/rangecheck.cpp
@@ -502,7 +502,7 @@ void RangeCheck::MergeEdgeAssertions(GenTreePtr tree, const ASSERT_VALARG_TP ass
     // Walk through the "assertions" to check if the apply.
     BitVecOps::Iter iter(m_pCompiler->apTraits, assertions);
     unsigned        index = 0;
-    while (iter.NextElem(m_pCompiler->apTraits, &index))
+    while (iter.NextElem(&index))
     {
         index++;