Optimize SwissMap iteration by another 5-10% for ARM

https://pastebin.com/fDvgWgHe

After having a chat with Dougall Johnson (https://twitter.com/dougallj/status/1534213050944802816), we realized that __clzll works with zero arguments per documentation:

https://developer.arm.com/documentation/101028/0009/Data-processing-intrinsics

```
Returns the number of leading zero bits in x. When x is zero it returns the argument width, i.e. 32 or 64.
```

Codegen improves https://godbolt.org/z/ebadf717Y

Thus we can use a little bit different construction not involving CLS but using more understandable CLZ and removing some operations.

PiperOrigin-RevId: 453879080
Change-Id: Ie2d7f834f63364d7bd50dd6a682c107985f21942

1 files changed, 1 insertions, 5 deletions

diff --git a/absl/container/internal/raw_hash_set_test.cc b/absl/container/internal/raw_hash_set_test.cc
index dc6bc3d2..f77ffbc1 100644
--- a/absl/container/internal/raw_hash_set_test.cc
+++ b/absl/container/internal/raw_hash_set_test.cc
@@ -266,20 +266,16 @@ TEST(Group, CountLeadingEmptyOrDeleted) {
 
   for (ctrl_t empty : empty_examples) {
     std::vector<ctrl_t> e(Group::kWidth, empty);
-    EXPECT_TRUE(IsEmptyOrDeleted(e[0]));
     EXPECT_EQ(Group::kWidth, Group{e.data()}.CountLeadingEmptyOrDeleted());
     for (ctrl_t full : full_examples) {
-      // First is always kEmpty or kDeleted.
-      for (size_t i = 1; i != Group::kWidth; ++i) {
+      for (size_t i = 0; i != Group::kWidth; ++i) {
         std::vector<ctrl_t> f(Group::kWidth, empty);
         f[i] = full;
-        EXPECT_TRUE(IsEmptyOrDeleted(f[0]));
         EXPECT_EQ(i, Group{f.data()}.CountLeadingEmptyOrDeleted());
       }
       std::vector<ctrl_t> f(Group::kWidth, empty);
       f[Group::kWidth * 2 / 3] = full;
       f[Group::kWidth / 2] = full;
-      EXPECT_TRUE(IsEmptyOrDeleted(f[0]));
       EXPECT_EQ(
           Group::kWidth / 2, Group{f.data()}.CountLeadingEmptyOrDeleted());
     }