update cfg(miri)-related comments

library/core/src/primitive_docs.rs

@@ -1777,7 +1777,7 @@ mod prim_ref {}
 /// However, a direct cast back is not possible. You need to use `transmute`:
 ///
 /// ```rust
-/// # #[cfg(not(miri))] { // FIXME: use strict provenance APIs once they are stable, then remove this `cfg`
+/// # #[cfg(not(miri))] { // disabled because it fails with -Zmiri-strict-provenance
 /// # let fnptr: fn(i32) -> i32 = |x| x+2;
 /// # let fnptr_addr = fnptr as usize;
 /// let fnptr = fnptr_addr as *const ();

library/coretests/tests/num/midpoint.rs

@@ -4,7 +4,7 @@
 //!  - midpoint(-a, -b) == -midpoint(a, b)
 
 #[test]
-#[cfg(not(miri))]
+#[cfg(not(miri))] // Miri is too slow
 fn midpoint_obvious_impl_i8() {
     for a in i8::MIN..=i8::MAX {
         for b in i8::MIN..=i8::MAX {
@@ -14,7 +14,7 @@ fn midpoint_obvious_impl_i8() {
 }
 
 #[test]
-#[cfg(not(miri))]
+#[cfg(not(miri))] // Miri is too slow
 fn midpoint_obvious_impl_u8() {
     for a in u8::MIN..=u8::MAX {
         for b in u8::MIN..=u8::MAX {
@@ -24,7 +24,7 @@ fn midpoint_obvious_impl_u8() {
 }
 
 #[test]
-#[cfg(not(miri))]
+#[cfg(not(miri))] // Miri is too slow
 fn midpoint_order_expectation_i8() {
     for a in i8::MIN..=i8::MAX {
         for b in i8::MIN..=i8::MAX {
@@ -34,7 +34,7 @@ fn midpoint_order_expectation_i8() {
 }
 
 #[test]
-#[cfg(not(miri))]
+#[cfg(not(miri))] // Miri is too slow
 fn midpoint_order_expectation_u8() {
     for a in u8::MIN..=u8::MAX {
         for b in u8::MIN..=u8::MAX {
@@ -44,7 +44,7 @@ fn midpoint_order_expectation_u8() {
 }
 
 #[test]
-#[cfg(not(miri))]
+#[cfg(not(miri))] // Miri is too slow
 fn midpoint_negative_expectation() {
     for a in 0..=i8::MAX {
         for b in 0..=i8::MAX {

src/tools/miri/src/bin/miri.rs

@@ -188,7 +188,7 @@ fn make_miri_codegen_backend(sess: &Session) -> Box<dyn CodegenBackend> {
             cfg.has_reliable_f128 = true;
             // We always provide the f16 intrinsics, but some are provided via the host,
             // so forward its reliability.
-            cfg.has_reliable_f16_math = cfg!(target_has_reliable_f16);
+            cfg.has_reliable_f16_math = cfg!(target_has_reliable_f16_math);
             // Many f128 operations are still missing.
             cfg.has_reliable_f128_math = false;
             cfg