Simplify MIR opt tests

This commit removes many cases of MIR opt tests emitting `.diff`s for more than one pass. These
tests cannot be `unit-test`s, and so they are easy to break, and they also provide little value due
to having excessively strong opinions over *how* a piece of code should be optimized.

Where reasonable, we instead add separate test files that only emit the `PreCodegen.after` MIR for
code where we want to track what the result of the net result of the optimization pipeline's output
is.

1 files changed, 49 insertions, 0 deletions

diff --git a/src/test/mir-opt/lower_array_len_e2e.array_bound.PreCodegen.after.mir b/src/test/mir-opt/lower_array_len_e2e.array_bound.PreCodegen.after.mir
new file mode 100644
index 00000000000..2c6c93cb1d8
--- /dev/null
+++ b/src/test/mir-opt/lower_array_len_e2e.array_bound.PreCodegen.after.mir
@@ -0,0 +1,49 @@
+// MIR for `array_bound` after PreCodegen
+
+fn array_bound(_1: usize, _2: &[u8; N]) -> u8 {
+    debug index => _1;                   // in scope 0 at $DIR/lower_array_len_e2e.rs:+0:36: +0:41
+    debug slice => _2;                   // in scope 0 at $DIR/lower_array_len_e2e.rs:+0:50: +0:55
+    let mut _0: u8;                      // return place in scope 0 at $DIR/lower_array_len_e2e.rs:+0:70: +0:72
+    let mut _3: bool;                    // in scope 0 at $DIR/lower_array_len_e2e.rs:+1:8: +1:27
+    let mut _4: usize;                   // in scope 0 at $DIR/lower_array_len_e2e.rs:+1:8: +1:13
+    let mut _5: usize;                   // in scope 0 at $DIR/lower_array_len_e2e.rs:+1:16: +1:27
+    let _6: usize;                       // in scope 0 at $DIR/lower_array_len_e2e.rs:+2:15: +2:20
+    let mut _7: usize;                   // in scope 0 at $DIR/lower_array_len_e2e.rs:+2:9: +2:21
+    let mut _8: bool;                    // in scope 0 at $DIR/lower_array_len_e2e.rs:+2:9: +2:21
+
+    bb0: {
+        StorageLive(_3);                 // scope 0 at $DIR/lower_array_len_e2e.rs:+1:8: +1:27
+        StorageLive(_4);                 // scope 0 at $DIR/lower_array_len_e2e.rs:+1:8: +1:13
+        _4 = _1;                         // scope 0 at $DIR/lower_array_len_e2e.rs:+1:8: +1:13
+        StorageLive(_5);                 // scope 0 at $DIR/lower_array_len_e2e.rs:+1:16: +1:27
+        _5 = const N;                    // scope 0 at $DIR/lower_array_len_e2e.rs:+1:16: +1:27
+        _3 = Lt(move _4, move _5);       // scope 0 at $DIR/lower_array_len_e2e.rs:+1:8: +1:27
+        StorageDead(_5);                 // scope 0 at $DIR/lower_array_len_e2e.rs:+1:26: +1:27
+        StorageDead(_4);                 // scope 0 at $DIR/lower_array_len_e2e.rs:+1:26: +1:27
+        switchInt(move _3) -> [false: bb3, otherwise: bb1]; // scope 0 at $DIR/lower_array_len_e2e.rs:+1:8: +1:27
+    }
+
+    bb1: {
+        StorageLive(_6);                 // scope 0 at $DIR/lower_array_len_e2e.rs:+2:15: +2:20
+        _6 = _1;                         // scope 0 at $DIR/lower_array_len_e2e.rs:+2:15: +2:20
+        _7 = const N;                    // scope 0 at $DIR/lower_array_len_e2e.rs:+2:9: +2:21
+        _8 = Lt(_6, _7);                 // scope 0 at $DIR/lower_array_len_e2e.rs:+2:9: +2:21
+        assert(move _8, "index out of bounds: the length is {} but the index is {}", move _7, _6) -> bb2; // scope 0 at $DIR/lower_array_len_e2e.rs:+2:9: +2:21
+    }
+
+    bb2: {
+        _0 = (*_2)[_6];                  // scope 0 at $DIR/lower_array_len_e2e.rs:+2:9: +2:21
+        StorageDead(_6);                 // scope 0 at $DIR/lower_array_len_e2e.rs:+3:5: +3:6
+        goto -> bb4;                     // scope 0 at $DIR/lower_array_len_e2e.rs:+1:5: +5:6
+    }
+
+    bb3: {
+        _0 = const 42_u8;                // scope 0 at $DIR/lower_array_len_e2e.rs:+4:9: +4:11
+        goto -> bb4;                     // scope 0 at $DIR/lower_array_len_e2e.rs:+1:5: +5:6
+    }
+
+    bb4: {
+        StorageDead(_3);                 // scope 0 at $DIR/lower_array_len_e2e.rs:+5:5: +5:6
+        return;                          // scope 0 at $DIR/lower_array_len_e2e.rs:+6:2: +6:2
+    }
+}