Rollup merge of rust-lang#96090 - JakobDegen:mir-tests, r=nagisa

Implement MIR opt unit tests

This implements rust-lang/compiler-team#502 .

There's not much to say here, this implementation does everything as proposed. I also added the flag to a bunch of existing tests (mostly those to which I could add it without causing huge diffs due to changes in line numbers). Summarizing the changes to test outputs:
 - Every time an `MirPatch` is created, it adds a cleanup block to the body if it did not exist already. If this block is unused (as is usually the case), it usually gets removed soon after by some pass calling `SimplifyCFG` for unrelated reasons (in many cases this cycle happens quite a few times for a single body). We now run `SimplifyCFG` less often, so those blocks end up in some of our outputs. I looked at changing `MirPatch` to not do this, but that seemed too complicated for this PR. I may still do that in a follow-up.
 - The `InstCombine` test had set `-C opt-level=0` in its flags and so there were no storage markers. I don't really see a good motivation for doing this, so bringing it back in line with what everything else does seems correct.
 - One of the `EarlyOtherwiseBranch` tests had `UnreachableProp` running on it. Preventing that kind of thing is the goal of this feature, so this seems fine.

For the remaining tests for which this feature might be useful, we can gradually migrate them as opportunities present themselves.

In terms of documentation, I plan on submitting a PR to the rustc dev guide in the near future documenting this and other recent changes to MIR. If there's any other places to update, do let me know

r? `@nagisa`

Author: matthiaskrgr

compiler/rustc_interface/src/tests.rs

@@ -752,6 +752,7 @@ fn test_debugging_options_tracking_hash() {
     tracked!(location_detail, LocationDetail { file: true, line: false, column: false });
     tracked!(merge_functions, Some(MergeFunctions::Disabled));
     tracked!(mir_emit_retag, true);
+    tracked!(mir_enable_passes, vec![("DestProp".to_string(), false)]);
     tracked!(mir_opt_level, Some(4));
     tracked!(move_size_limit, Some(4096));
     tracked!(mutable_noalias, Some(true));

compiler/rustc_mir_transform/src/pass_manager.rs

@@ -77,17 +77,30 @@ pub fn run_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, passes: &[&dyn
     let mut cnt = 0;
 
     let validate = tcx.sess.opts.debugging_opts.validate_mir;
+    let overridden_passes = &tcx.sess.opts.debugging_opts.mir_enable_passes;
+    trace!(?overridden_passes);
 
     if validate {
         validate_body(tcx, body, format!("start of phase transition from {:?}", start_phase));
     }
 
     for pass in passes {
-        if !pass.is_enabled(&tcx.sess) {
-            continue;
-        }
-
         let name = pass.name();
+
+        if let Some((_, polarity)) = overridden_passes.iter().rev().find(|(s, _)| s == &*name) {
+            trace!(
+                pass = %name,
+                "{} as requested by flag",
+                if *polarity { "Running" } else { "Not running" },
+            );
+            if !polarity {
+                continue;
+            }
+        } else {
+            if !pass.is_enabled(&tcx.sess) {
+                continue;
+            }
+        }
         let dump_enabled = pass.is_mir_dump_enabled();
 
         if dump_enabled {

compiler/rustc_session/src/options.rs

@@ -368,6 +368,8 @@ mod desc {
     pub const parse_opt_langid: &str = "a language identifier";
     pub const parse_opt_pathbuf: &str = "a path";
     pub const parse_list: &str = "a space-separated list of strings";
+    pub const parse_list_with_polarity: &str =
+        "a comma-separated list of strings, with elements beginning with + or -";
     pub const parse_opt_comma_list: &str = "a comma-separated list of strings";
     pub const parse_number: &str = "a number";
     pub const parse_opt_number: &str = parse_number;
@@ -529,6 +531,19 @@ mod parse {
         }
     }
 
+    crate fn parse_list_with_polarity(slot: &mut Vec<(String, bool)>, v: Option<&str>) -> bool {
+        match v {
+            Some(s) => {
+                for s in s.split(",") {
+                    let Some(pass_name) = s.strip_prefix(&['+', '-'][..]) else { return false };
+                    slot.push((pass_name.to_string(), &s[..1] == "+"));
+                }
+                true
+            }
+            None => false,
+        }
+    }
+
     crate fn parse_location_detail(ld: &mut LocationDetail, v: Option<&str>) -> bool {
         if let Some(v) = v {
             ld.line = false;
@@ -1318,6 +1333,10 @@ options! {
     mir_emit_retag: bool = (false, parse_bool, [TRACKED],
         "emit Retagging MIR statements, interpreted e.g., by miri; implies -Zmir-opt-level=0 \
         (default: no)"),
+    mir_enable_passes: Vec<(String, bool)> = (Vec::new(), parse_list_with_polarity, [TRACKED],
+        "use like `-Zmir-enable-passes=+DestProp,-InstCombine`. Forces the specified passes to be \
+        enabled, overriding all other checks. Passes that are not specified are enabled or \
+        disabled by other flags as usual."),
     mir_opt_level: Option<usize> = (None, parse_opt_number, [TRACKED],
         "MIR optimization level (0-4; default: 1 in non optimized builds and 2 in optimized builds)"),
     move_size_limit: Option<usize> = (None, parse_opt_number, [TRACKED],

src/test/mir-opt/combine_clone_of_primitives.rs

@@ -1,4 +1,4 @@
-// compile-flags: -C opt-level=0 -Z inline_mir=no
+// unit-test: InstCombine
 // ignore-wasm32 compiled with panic=abort by default
 
 // EMIT_MIR combine_clone_of_primitives.{impl#0}-clone.InstCombine.diff

src/test/mir-opt/combine_clone_of_primitives.{impl#0}-clone.InstCombine.diff

@@ -23,9 +23,15 @@
       }
 
       bb0: {
+          StorageLive(_2);                 // scope 0 at $DIR/combine_clone_of_primitives.rs:8:5: 8:9
           _2 = &((*_1).0: T);              // scope 0 at $DIR/combine_clone_of_primitives.rs:8:5: 8:9
+          StorageLive(_3);                 // scope 0 at $DIR/combine_clone_of_primitives.rs:9:5: 9:11
           _3 = &((*_1).1: u64);            // scope 0 at $DIR/combine_clone_of_primitives.rs:9:5: 9:11
+          StorageLive(_4);                 // scope 0 at $DIR/combine_clone_of_primitives.rs:10:5: 10:16
           _4 = &((*_1).2: [f32; 3]);       // scope 0 at $DIR/combine_clone_of_primitives.rs:10:5: 10:16
+          StorageLive(_5);                 // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:9
+          StorageLive(_6);                 // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:9
+          StorageLive(_7);                 // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:9
 -         _7 = &(*_2);                     // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:9
 -         _6 = &(*_7);                     // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:9
 +         _7 = _2;                         // scope 1 at $DIR/combine_clone_of_primitives.rs:8:5: 8:9
@@ -37,6 +43,10 @@
       }
 
       bb1: {
+          StorageDead(_6);                 // scope 1 at $DIR/combine_clone_of_primitives.rs:8:8: 8:9
+          StorageLive(_8);                 // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:11
+          StorageLive(_9);                 // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:11
+          StorageLive(_10);                // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:11
 -         _10 = &(*_3);                    // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:11
 -         _9 = &(*_10);                    // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:11
 -         _8 = <u64 as Clone>::clone(move _9) -> [return: bb2, unwind: bb4]; // scope 1 at $DIR/combine_clone_of_primitives.rs:9:5: 9:11
@@ -50,6 +60,10 @@
       }
 
       bb2: {
+          StorageDead(_9);                 // scope 1 at $DIR/combine_clone_of_primitives.rs:9:10: 9:11
+          StorageLive(_11);                // scope 1 at $DIR/combine_clone_of_primitives.rs:10:5: 10:16
+          StorageLive(_12);                // scope 1 at $DIR/combine_clone_of_primitives.rs:10:5: 10:16
+          StorageLive(_13);                // scope 1 at $DIR/combine_clone_of_primitives.rs:10:5: 10:16
 -         _13 = &(*_4);                    // scope 1 at $DIR/combine_clone_of_primitives.rs:10:5: 10:16
 -         _12 = &(*_13);                   // scope 1 at $DIR/combine_clone_of_primitives.rs:10:5: 10:16
 -         _11 = <[f32; 3] as Clone>::clone(move _12) -> [return: bb3, unwind: bb4]; // scope 1 at $DIR/combine_clone_of_primitives.rs:10:5: 10:16
@@ -63,10 +77,20 @@
       }
 
       bb3: {
+          StorageDead(_12);                // scope 1 at $DIR/combine_clone_of_primitives.rs:10:15: 10:16
           Deinit(_0);                      // scope 1 at $DIR/combine_clone_of_primitives.rs:6:10: 6:15
           (_0.0: T) = move _5;             // scope 1 at $DIR/combine_clone_of_primitives.rs:6:10: 6:15
           (_0.1: u64) = move _8;           // scope 1 at $DIR/combine_clone_of_primitives.rs:6:10: 6:15
           (_0.2: [f32; 3]) = move _11;     // scope 1 at $DIR/combine_clone_of_primitives.rs:6:10: 6:15
+          StorageDead(_13);                // scope 1 at $DIR/combine_clone_of_primitives.rs:6:14: 6:15
+          StorageDead(_11);                // scope 1 at $DIR/combine_clone_of_primitives.rs:6:14: 6:15
+          StorageDead(_10);                // scope 1 at $DIR/combine_clone_of_primitives.rs:6:14: 6:15
+          StorageDead(_8);                 // scope 1 at $DIR/combine_clone_of_primitives.rs:6:14: 6:15
+          StorageDead(_7);                 // scope 1 at $DIR/combine_clone_of_primitives.rs:6:14: 6:15
+          StorageDead(_5);                 // scope 1 at $DIR/combine_clone_of_primitives.rs:6:14: 6:15
+          StorageDead(_4);                 // scope 0 at $DIR/combine_clone_of_primitives.rs:6:14: 6:15
+          StorageDead(_3);                 // scope 0 at $DIR/combine_clone_of_primitives.rs:6:14: 6:15
+          StorageDead(_2);                 // scope 0 at $DIR/combine_clone_of_primitives.rs:6:14: 6:15
           return;                          // scope 0 at $DIR/combine_clone_of_primitives.rs:6:15: 6:15
       }
 

src/test/mir-opt/early_otherwise_branch.opt1.EarlyOtherwiseBranch.diff

@@ -68,8 +68,10 @@
 +     bb3: {
           StorageDead(_3);                 // scope 0 at $DIR/early_otherwise_branch.rs:8:1: 8:2
           return;                          // scope 0 at $DIR/early_otherwise_branch.rs:8:2: 8:2
-+     }
-+ 
+      }
+  
+-     bb5 (cleanup): {
+-         resume;                          // scope 0 at $DIR/early_otherwise_branch.rs:3:1: 8:2
 +     bb4: {
 +         StorageDead(_11);                // scope 0 at $DIR/early_otherwise_branch.rs:4:5: 4:17
 +         switchInt(_7) -> [1_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:4:5: 4:17

src/test/mir-opt/early_otherwise_branch.opt2.EarlyOtherwiseBranch.diff

@@ -32,7 +32,7 @@
           StorageDead(_5);                 // scope 0 at $DIR/early_otherwise_branch.rs:12:16: 12:17
           StorageDead(_4);                 // scope 0 at $DIR/early_otherwise_branch.rs:12:16: 12:17
           _8 = discriminant((_3.0: std::option::Option<u32>)); // scope 0 at $DIR/early_otherwise_branch.rs:12:11: 12:17
--         switchInt(move _8) -> [0_isize: bb1, 1_isize: bb3, otherwise: bb7]; // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
+-         switchInt(move _8) -> [0_isize: bb1, 1_isize: bb3, otherwise: bb2]; // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
 +         StorageLive(_11);                // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
 +         _11 = discriminant((_3.1: std::option::Option<u32>)); // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
 +         StorageLive(_12);                // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
@@ -84,8 +84,8 @@
           return;                          // scope 0 at $DIR/early_otherwise_branch.rs:17:2: 17:2
       }
 
--     bb7: {
--         unreachable;                     // scope 0 at $DIR/early_otherwise_branch.rs:15:14: 15:15
+-     bb7 (cleanup): {
+-         resume;                          // scope 0 at $DIR/early_otherwise_branch.rs:11:1: 17:2
 +     bb5: {
 +         StorageDead(_12);                // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17
 +         switchInt(_8) -> [0_isize: bb3, 1_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:12:5: 12:17

src/test/mir-opt/early_otherwise_branch.opt3.EarlyOtherwiseBranch.diff

@@ -68,8 +68,10 @@
 +     bb3: {
           StorageDead(_3);                 // scope 0 at $DIR/early_otherwise_branch.rs:26:1: 26:2
           return;                          // scope 0 at $DIR/early_otherwise_branch.rs:26:2: 26:2
-+     }
-+ 
+      }
+  
+-     bb5 (cleanup): {
+-         resume;                          // scope 0 at $DIR/early_otherwise_branch.rs:21:1: 26:2
 +     bb4: {
 +         StorageDead(_11);                // scope 0 at $DIR/early_otherwise_branch.rs:22:5: 22:17
 +         switchInt(_7) -> [1_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch.rs:22:5: 22:17

src/test/mir-opt/early_otherwise_branch.rs

@@ -1,4 +1,4 @@
-// compile-flags: -Z mir-opt-level=4 -Z unsound-mir-opts
+// unit-test: EarlyOtherwiseBranch
 // EMIT_MIR early_otherwise_branch.opt1.EarlyOtherwiseBranch.diff
 fn opt1(x: Option<u32>, y: Option<u32>) -> u32 {
     match (x, y) {

src/test/mir-opt/early_otherwise_branch_3_element_tuple.opt1.EarlyOtherwiseBranch.diff

@@ -90,8 +90,10 @@
 +     bb4: {
           StorageDead(_4);                 // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:9:1: 9:2
           return;                          // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:9:2: 9:2
-+     }
-+ 
+      }
+  
+-     bb6 (cleanup): {
+-         resume;                          // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:4:1: 9:2
 +     bb5: {
 +         StorageDead(_15);                // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:5:5: 5:20
 +         switchInt(_10) -> [1_isize: bb2, otherwise: bb1]; // scope 0 at $DIR/early_otherwise_branch_3_element_tuple.rs:5:5: 5:20