8 files changed, 28 insertions, 9 deletions
diff --git a/src/libcore/tests/fmt/mod.rs b/src/libcore/tests/fmt/mod.rs
index b10b63fc484..3baa445e652 100644
--- a/src/libcore/tests/fmt/mod.rs
+++ b/src/libcore/tests/fmt/mod.rs
@@ -1,4 +1,4 @@
-#![cfg(not(miri))]
+#![cfg(not(miri))] // FIXME: A bug in Miri breaks padding in string formatting
 
 mod builders;
 mod float;
diff --git a/src/libcore/tests/hash/mod.rs b/src/libcore/tests/hash/mod.rs
index bf3039a7e51..1000088e6b0 100644
--- a/src/libcore/tests/hash/mod.rs
+++ b/src/libcore/tests/hash/mod.rs
@@ -1,5 +1,3 @@
-#![cfg(not(miri))]
-
 mod sip;
 
 use std::hash::{Hash, Hasher};
@@ -75,9 +73,11 @@ fn test_writer_hasher() {
     let cs: &mut [u8] = &mut [1, 2, 3];
     let ptr = cs.as_ptr();
     let slice_ptr = cs as *const [u8];
+    #[cfg(not(miri))] // Miri cannot hash pointers
     assert_eq!(hash(&slice_ptr), hash(&ptr) + cs.len() as u64);
 
     let slice_ptr = cs as *mut [u8];
+    #[cfg(not(miri))] // Miri cannot hash pointers
     assert_eq!(hash(&slice_ptr), hash(&ptr) + cs.len() as u64);
 }
 
diff --git a/src/libcore/tests/iter.rs b/src/libcore/tests/iter.rs
index bc951829bd7..9b76a4af988 100644
--- a/src/libcore/tests/iter.rs
+++ b/src/libcore/tests/iter.rs
@@ -1661,9 +1661,7 @@ fn test_range_step() {
     assert_eq!((1..21).rev().step_by(5).collect::<Vec<isize>>(), [20, 15, 10, 5]);
     assert_eq!((1..21).rev().step_by(6).collect::<Vec<isize>>(), [20, 14, 8, 2]);
     assert_eq!((200..255).step_by(50).collect::<Vec<u8>>(), [200, 250]);
-    #[cfg(not(miri))] // Miri cannot compare empty slices
     assert_eq!((200..-5).step_by(1).collect::<Vec<isize>>(), []);
-    #[cfg(not(miri))] // Miri cannot compare empty slices
     assert_eq!((200..200).step_by(1).collect::<Vec<isize>>(), []);
 
     assert_eq!((0..20).step_by(1).size_hint(), (20, Some(20)));
diff --git a/src/libcore/tests/num/bignum.rs b/src/libcore/tests/num/bignum.rs
index b873f1dd065..956c22c9982 100644
--- a/src/libcore/tests/num/bignum.rs
+++ b/src/libcore/tests/num/bignum.rs
@@ -3,6 +3,7 @@ use core::num::bignum::tests::Big8x3 as Big;
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_from_u64_overflow() {
     Big::from_u64(0x1000000);
 }
@@ -19,12 +20,14 @@ fn test_add() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_add_overflow_1() {
     Big::from_small(1).add(&Big::from_u64(0xffffff));
 }
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_add_overflow_2() {
     Big::from_u64(0xffffff).add(&Big::from_small(1));
 }
@@ -42,6 +45,7 @@ fn test_add_small() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_add_small_overflow() {
     Big::from_u64(0xffffff).add_small(1);
 }
@@ -57,12 +61,14 @@ fn test_sub() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_sub_underflow_1() {
     Big::from_u64(0x10665).sub(&Big::from_u64(0x10666));
 }
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_sub_underflow_2() {
     Big::from_small(0).sub(&Big::from_u64(0x123456));
 }
@@ -76,6 +82,7 @@ fn test_mul_small() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_mul_small_overflow() {
     Big::from_u64(0x800000).mul_small(2);
 }
@@ -94,12 +101,14 @@ fn test_mul_pow2() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_mul_pow2_overflow_1() {
     Big::from_u64(0x1).mul_pow2(24);
 }
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_mul_pow2_overflow_2() {
     Big::from_u64(0x123).mul_pow2(16);
 }
@@ -118,12 +127,14 @@ fn test_mul_pow5() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_mul_pow5_overflow_1() {
     Big::from_small(1).mul_pow5(12);
 }
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_mul_pow5_overflow_2() {
     Big::from_small(230).mul_pow5(8);
 }
@@ -141,12 +152,14 @@ fn test_mul_digits() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_mul_digits_overflow_1() {
     Big::from_u64(0x800000).mul_digits(&[2]);
 }
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_mul_digits_overflow_2() {
     Big::from_u64(0x1000).mul_digits(&[0, 0x10]);
 }
@@ -206,6 +219,7 @@ fn test_get_bit() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))] // Miri does not support panics
 fn test_get_bit_out_of_range() {
     Big::from_small(42).get_bit(24);
 }
diff --git a/src/libcore/tests/num/dec2flt/mod.rs b/src/libcore/tests/num/dec2flt/mod.rs
index 8f1cd32c356..faeaabbf95a 100644
--- a/src/libcore/tests/num/dec2flt/mod.rs
+++ b/src/libcore/tests/num/dec2flt/mod.rs
@@ -52,6 +52,7 @@ fn large() {
 }
 
 #[test]
+#[cfg(not(miri))] // Miri is too slow
 fn subnormals() {
     test_literal!(5e-324);
     test_literal!(91e-324);
@@ -63,6 +64,7 @@ fn subnormals() {
 }
 
 #[test]
+#[cfg(not(miri))] // Miri is too slow
 fn infinity() {
     test_literal!(1e400);
     test_literal!(1e309);
diff --git a/src/libcore/tests/num/flt2dec/mod.rs b/src/libcore/tests/num/flt2dec/mod.rs
index fed9ce73b2a..d362c7994d8 100644
--- a/src/libcore/tests/num/flt2dec/mod.rs
+++ b/src/libcore/tests/num/flt2dec/mod.rs
@@ -1,3 +1,5 @@
+#![cfg(not(miri))] // Miri does not implement ldexp, which most tests here need
+
 use std::prelude::v1::*;
 use std::{str, i16, f32, f64, fmt};
 
diff --git a/src/libcore/tests/num/mod.rs b/src/libcore/tests/num/mod.rs
index ab638e06cc1..a17c094679e 100644
--- a/src/libcore/tests/num/mod.rs
+++ b/src/libcore/tests/num/mod.rs
@@ -1,5 +1,3 @@
-#![cfg(not(miri))]
-
 use core::convert::{TryFrom, TryInto};
 use core::cmp::PartialEq;
 use core::fmt::Debug;
diff --git a/src/libcore/tests/ptr.rs b/src/libcore/tests/ptr.rs
index 57845590822..2c53e4832a8 100644
--- a/src/libcore/tests/ptr.rs
+++ b/src/libcore/tests/ptr.rs
@@ -1,5 +1,3 @@
-#![cfg(not(miri))]
-
 use core::ptr::*;
 use core::cell::RefCell;
 
@@ -42,6 +40,7 @@ fn test() {
 }
 
 #[test]
+#[cfg(not(miri))] // This test performs invalid OOB pointer arithmetic
 fn test_is_null() {
     let p: *const isize = null();
     assert!(p.is_null());
@@ -147,6 +146,7 @@ fn test_as_ref() {
 }
 
 #[test]
+#[cfg(not(miri))] // This test is UB according to Stacked Borrows
 fn test_as_mut() {
     unsafe {
         let p: *mut isize = null_mut();
@@ -208,6 +208,7 @@ fn test_ptr_addition() {
 }
 
 #[test]
+#[cfg(not(miri))] // This test performs invalid OOB pointer arithmetic
 fn test_ptr_subtraction() {
     unsafe {
         let xs = vec![0,1,2,3,4,5,6,7,8,9];
@@ -251,6 +252,7 @@ fn test_unsized_nonnull() {
 
 #[test]
 #[allow(warnings)]
+#[cfg(not(miri))] // Miri cannot hash pointers
 // Have a symbol for the test below. It doesn’t need to be an actual variadic function, match the
 // ABI, or even point to an actual executable code, because the function itself is never invoked.
 #[no_mangle]
@@ -290,6 +292,7 @@ fn write_unaligned_drop() {
 }
 
 #[test]
+#[cfg(not(miri))] // Miri cannot compute actual alignment of an allocation
 fn align_offset_zst() {
     // For pointers of stride = 0, the pointer is already aligned or it cannot be aligned at
     // all, because no amount of elements will align the pointer.
@@ -304,6 +307,7 @@ fn align_offset_zst() {
 }
 
 #[test]
+#[cfg(not(miri))] // Miri cannot compute actual alignment of an allocation
 fn align_offset_stride1() {
     // For pointers of stride = 1, the pointer can always be aligned. The offset is equal to
     // number of bytes.
@@ -320,6 +324,7 @@ fn align_offset_stride1() {
 }
 
 #[test]
+#[cfg(not(miri))] // Miri is too slow
 fn align_offset_weird_strides() {
     #[repr(packed)]
     struct A3(u16, u8);