Rollup merge of #74974 - RalfJung:miri-tests, r=Mark-Simulacrum

Make tests faster in Miri

Reduce some test iteration counts in Miri.

library/alloc/src/collections/vec_deque/tests.rs

@@ -107,7 +107,8 @@ fn test_insert() {
     let cap = tester.capacity();
 
     // len is the length *after* insertion
-    for len in 1..cap {
+    let minlen = if cfg!(miri) { cap - 1 } else { 1 }; // Miri is too slow
+    for len in minlen..cap {
         // 0, 1, 2, .., len - 1
         let expected = (0..).take(len).collect::<VecDeque<_>>();
         for tail_pos in 0..cap {
@@ -221,7 +222,8 @@ fn test_remove() {
     let cap = tester.capacity();
 
     // len is the length *after* removal
-    for len in 0..cap - 1 {
+    let minlen = if cfg!(miri) { cap - 2 } else { 0 }; // Miri is too slow
+    for len in minlen..cap - 1 {
         // 0, 1, 2, .., len - 1
         let expected = (0..).take(len).collect::<VecDeque<_>>();
         for tail_pos in 0..cap {
@@ -251,7 +253,8 @@ fn test_range() {
     let mut tester: VecDeque<usize> = VecDeque::with_capacity(7);
 
     let cap = tester.capacity();
-    for len in 0..=cap {
+    let minlen = if cfg!(miri) { cap - 1 } else { 0 }; // Miri is too slow
+    for len in minlen..=cap {
         for tail in 0..=cap {
             for start in 0..=len {
                 for end in start..=len {
@@ -384,7 +387,8 @@ fn test_split_off() {
     let cap = tester.capacity();
 
     // len is the length *before* splitting
-    for len in 0..cap {
+    let minlen = if cfg!(miri) { cap - 1 } else { 0 }; // Miri is too slow
+    for len in minlen..cap {
         // index to split at
         for at in 0..=len {
             // 0, 1, 2, .., at - 1 (may be empty)
@@ -495,8 +499,9 @@ fn test_vec_from_vecdeque() {
 fn test_clone_from() {
     let m = vec![1; 8];
     let n = vec![2; 12];
-    for pfv in 0..8 {
-        for pfu in 0..8 {
+    let limit = if cfg!(miri) { 4 } else { 8 }; // Miri is too slow
+    for pfv in 0..limit {
+        for pfu in 0..limit {
             for longer in 0..2 {
                 let (vr, ur) = if longer == 0 { (&m, &n) } else { (&n, &m) };
                 let mut v = VecDeque::from(vr.clone());

library/alloc/tests/slice.rs

@@ -1721,8 +1721,8 @@ fn panic_safe() {
 
     let mut rng = thread_rng();
 
-    // Miri is too slow
-    let lens = if cfg!(miri) { (1..10).chain(20..21) } else { (1..20).chain(70..MAX_LEN) };
+    // Miri is too slow (but still need to `chain` to make the types match)
+    let lens = if cfg!(miri) { (1..10).chain(0..0) } else { (1..20).chain(70..MAX_LEN) };
     let moduli: &[u32] = if cfg!(miri) { &[5] } else { &[5, 20, 50] };
 
     for len in lens {

library/core/tests/num/flt2dec/random.rs

@@ -188,7 +188,7 @@ fn exact_f32_random_equivalence_test() {
 fn exact_f64_random_equivalence_test() {
     use core::num::flt2dec::strategy::dragon::format_exact as fallback;
     // Miri is too slow
-    let n = if cfg!(miri) { 3 } else { 1_000 };
+    let n = if cfg!(miri) { 2 } else { 1_000 };
 
     for k in 1..21 {
         f64_random_equivalence_test(

library/core/tests/num/flt2dec/strategy/grisu.rs

@@ -2,6 +2,7 @@ use super::super::*;
 use core::num::flt2dec::strategy::grisu::*;
 
 #[test]
+#[cfg_attr(miri, ignore)] // Miri is too slow
 fn test_cached_power() {
     assert_eq!(CACHED_POW10.first().unwrap().1, CACHED_POW10_FIRST_E);
     assert_eq!(CACHED_POW10.last().unwrap().1, CACHED_POW10_LAST_E);

library/core/tests/slice.rs

@@ -1358,15 +1358,15 @@ fn sort_unstable() {
     use core::slice::heapsort;
     use rand::{rngs::StdRng, seq::SliceRandom, Rng, SeedableRng};
 
-    // Miri is too slow
-    let large_range = if cfg!(miri) { 0..0 } else { 500..510 };
+    // Miri is too slow (but still need to `chain` to make the types match)
+    let lens = if cfg!(miri) { (2..20).chain(0..0) } else { (2..25).chain(500..510) };
     let rounds = if cfg!(miri) { 1 } else { 100 };
 
     let mut v = [0; 600];
     let mut tmp = [0; 600];
     let mut rng = StdRng::from_entropy();
 
-    for len in (2..25).chain(large_range) {
+    for len in lens {
         let v = &mut v[0..len];
         let tmp = &mut tmp[0..len];