Rollup merge of #100827 - JakobDegen:better-tests, r=wesleywiser

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 end to end effect of the optimization pipeline on the example code is.

r? `````@wesleywiser`````

1 files changed, 0 insertions, 22 deletions

diff --git a/src/test/mir-opt/lower_array_len.array_len.SimplifyLocals.diff b/src/test/mir-opt/lower_array_len.array_len.SimplifyLocals.diff
deleted file mode 100644
index 09d571d20a3..00000000000
--- a/src/test/mir-opt/lower_array_len.array_len.SimplifyLocals.diff
+++ /dev/null
@@ -1,22 +0,0 @@
-- // MIR for `array_len` before SimplifyLocals
-+ // MIR for `array_len` after SimplifyLocals
-  
-  fn array_len(_1: &[u8; N]) -> usize {
-      debug arr => _1;                     // in scope 0 at $DIR/lower_array_len.rs:+0:34: +0:37
-      let mut _0: usize;                   // return place in scope 0 at $DIR/lower_array_len.rs:+0:52: +0:57
--     let mut _2: &[u8];                   // in scope 0 at $DIR/lower_array_len.rs:+1:5: +1:14
--     let mut _3: &[u8; N];                // in scope 0 at $DIR/lower_array_len.rs:+1:5: +1:14
--     let mut _4: &[u8; N];                // in scope 0 at $DIR/lower_array_len.rs:+1:5: +1:14
-  
-      bb0: {
--         StorageLive(_2);                 // scope 0 at $DIR/lower_array_len.rs:+1:5: +1:14
--         StorageLive(_3);                 // scope 0 at $DIR/lower_array_len.rs:+1:5: +1:14
--         StorageLive(_4);                 // scope 0 at $DIR/lower_array_len.rs:+1:5: +1:14
--         StorageDead(_3);                 // scope 0 at $DIR/lower_array_len.rs:+1:7: +1:8
-          _0 = const N;                    // scope 0 at $DIR/lower_array_len.rs:+1:5: +1:14
--         StorageDead(_4);                 // scope 0 at $DIR/lower_array_len.rs:+1:5: +1:14
--         StorageDead(_2);                 // scope 0 at $DIR/lower_array_len.rs:+1:13: +1:14
-          return;                          // scope 0 at $DIR/lower_array_len.rs:+2:2: +2:2
-      }
-  }
-