diff --git a/library/core/src/slice/ascii.rs b/library/core/src/slice/ascii.rs
index 3f3f5a8c441d..8b713947cd9c 100644
--- a/library/core/src/slice/ascii.rs
+++ b/library/core/src/slice/ascii.rs
@@ -103,6 +103,7 @@ impl [u8] {
         let (other_chunks, _) = other.as_chunks::<N>();
 
         // Branchless check to encourage auto-vectorization
+        #[inline(always)]
         const fn eq_ignore_ascii_inner(lhs: &[u8; N], rhs: &[u8; N]) -> bool {
             let mut equal_ascii = true;
             let mut j = 0;
diff --git a/library/coretests/benches/ascii.rs b/library/coretests/benches/ascii.rs
index 17a520922bfa..64bdc7fed118 100644
--- a/library/coretests/benches/ascii.rs
+++ b/library/coretests/benches/ascii.rs
@@ -1,4 +1,3 @@
-mod eq_ignore_ascii_case;
 mod is_ascii;
 
 // Lower-case ASCII 'a' is the first byte that has its highest bit set
diff --git a/library/coretests/benches/ascii/eq_ignore_ascii_case.rs b/library/coretests/benches/ascii/eq_ignore_ascii_case.rs
deleted file mode 100644
index a51acb1e8463..000000000000
--- a/library/coretests/benches/ascii/eq_ignore_ascii_case.rs
+++ /dev/null
@@ -1,56 +0,0 @@
-use test::Bencher;
-
-#[bench]
-fn bench_str_under_8_bytes_eq(b: &mut Bencher) {
-    let s = "foo";
-    let other = "FOo";
-    b.iter(|| {
-        assert!(s.eq_ignore_ascii_case(other));
-    })
-}
-
-#[bench]
-fn bench_str_of_8_bytes_eq(b: &mut Bencher) {
-    let s = "foobar78";
-    let other = "FOObAr78";
-    b.iter(|| {
-        assert!(s.eq_ignore_ascii_case(other));
-    })
-}
-
-#[bench]
-fn bench_str_17_bytes_eq(b: &mut Bencher) {
-    let s = "performance-criti";
-    let other = "performANce-cRIti";
-    b.iter(|| {
-        assert!(s.eq_ignore_ascii_case(other));
-    })
-}
-
-#[bench]
-fn bench_str_31_bytes_eq(b: &mut Bencher) {
-    let s = "foobarbazquux02foobarbazquux025";
-    let other = "fooBARbazQuuX02fooBARbazQuuX025";
-    b.iter(|| {
-        assert!(s.eq_ignore_ascii_case(other));
-    })
-}
-
-#[bench]
-fn bench_long_str_eq(b: &mut Bencher) {
-    let s = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor \
-             incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud \
-             exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute \
-             irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla \
-             pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui \
-             officia deserunt mollit anim id est laborum.";
-    let other = "Lorem ipsum dolor sit amet, CONSECTETUR adipisicing elit, sed do eiusmod tempor \
-             incididunt ut labore et dolore MAGNA aliqua. Ut enim ad MINIM veniam, quis nostrud \
-             exercitation ullamco LABORIS nisi ut aliquip ex ea commodo consequat. Duis aute \
-             irure dolor in reprehenderit in voluptate velit esse cillum DOLORE eu fugiat nulla \
-             pariatur. Excepteur sint occaecat CUPIDATAT non proident, sunt in culpa qui \
-             officia deserunt mollit anim id est laborum.";
-    b.iter(|| {
-        assert!(s.eq_ignore_ascii_case(other));
-    })
-}
diff --git a/library/coretests/benches/str.rs b/library/coretests/benches/str.rs
index 2f7d9d56a70b..bf45a8f0a79b 100644
--- a/library/coretests/benches/str.rs
+++ b/library/coretests/benches/str.rs
@@ -5,6 +5,7 @@ use test::{Bencher, black_box};
 mod char_count;
 mod corpora;
 mod debug;
+mod eq_ignore_ascii_case;
 mod iter;
 
 #[bench]
diff --git a/library/coretests/benches/str/eq_ignore_ascii_case.rs b/library/coretests/benches/str/eq_ignore_ascii_case.rs
new file mode 100644
index 000000000000..29129b933bc4
--- /dev/null
+++ b/library/coretests/benches/str/eq_ignore_ascii_case.rs
@@ -0,0 +1,45 @@
+use test::{Bencher, black_box};
+
+use super::corpora::*;
+
+#[bench]
+fn bench_str_under_8_bytes_eq(b: &mut Bencher) {
+    let s = black_box("foo");
+    let other = black_box("foo");
+    b.iter(|| assert!(s.eq_ignore_ascii_case(other)))
+}
+
+#[bench]
+fn bench_str_of_8_bytes_eq(b: &mut Bencher) {
+    let s = black_box(en::TINY);
+    let other = black_box(en::TINY);
+    b.iter(|| assert!(s.eq_ignore_ascii_case(other)))
+}
+
+#[bench]
+fn bench_str_17_bytes_eq(b: &mut Bencher) {
+    let s = black_box(&en::SMALL[..17]);
+    let other = black_box(&en::SMALL[..17]);
+    b.iter(|| assert!(s.eq_ignore_ascii_case(other)))
+}
+
+#[bench]
+fn bench_str_31_bytes_eq(b: &mut Bencher) {
+    let s = black_box(&en::SMALL[..31]);
+    let other = black_box(&en::SMALL[..31]);
+    b.iter(|| assert!(s.eq_ignore_ascii_case(other)))
+}
+
+#[bench]
+fn bench_medium_str_eq(b: &mut Bencher) {
+    let s = black_box(en::MEDIUM);
+    let other = black_box(en::MEDIUM);
+    b.iter(|| assert!(s.eq_ignore_ascii_case(other)))
+}
+
+#[bench]
+fn bench_large_str_eq(b: &mut Bencher) {
+    let s = black_box(en::LARGE);
+    let other = black_box(en::LARGE);
+    b.iter(|| assert!(s.eq_ignore_ascii_case(other)))
+}
diff --git a/tests/codegen-llvm/lib-optimizations/eq_ignore_ascii_case.rs b/tests/codegen-llvm/lib-optimizations/eq_ignore_ascii_case.rs
index b733f1812c92..d4ac5d64585d 100644
--- a/tests/codegen-llvm/lib-optimizations/eq_ignore_ascii_case.rs
+++ b/tests/codegen-llvm/lib-optimizations/eq_ignore_ascii_case.rs
@@ -2,13 +2,15 @@
 //@ only-x86_64
 #![crate_type = "lib"]
 
-// Ensure that the optimized variant of the function gets auto-vectorized.
+// Ensure that the optimized variant of the function gets auto-vectorized and
+// that the inner helper function is inlined.
 // CHECK-LABEL: @eq_ignore_ascii_case_autovectorized
 #[no_mangle]
 pub fn eq_ignore_ascii_case_autovectorized(s: &str, other: &str) -> bool {
     // CHECK: load <16 x i8>
     // CHECK: load <16 x i8>
     // CHECK: bitcast <16 x i1>
+    // CHECK-NOT: call {{.*}}eq_ignore_ascii_inner
     // CHECK-NOT: panic
     s.eq_ignore_ascii_case(other)
 }