Simplify generator_drop since it won't be optimized.

Author: cjgillot

compiler/rustc_mir_transform/src/generator.rs

@@ -967,7 +967,8 @@ fn create_generator_drop_shim<'tcx>(
 
     // Make sure we remove dead blocks to remove
     // unrelated code from the resume part of the function
-    simplify::remove_dead_blocks(tcx, &mut body);
+    simplify::simplify_cfg(tcx, &mut body);
+    simplify::simplify_locals(&mut body, tcx);
 
     body
 }

src/test/mir-opt/generator_drop_cleanup.main-{closure#0}.generator_drop.0.mir

@@ -17,69 +17,33 @@
 
 fn main::{closure#0}(_1: *mut [generator@$DIR/generator-drop-cleanup.rs:10:15: 10:17]) -> () {
     let mut _0: ();                      // return place in scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
-    let mut _2: ();                      // in scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
-    let _3: std::string::String;         // in scope 0 at $DIR/generator-drop-cleanup.rs:11:13: 11:15
-    let _4: ();                          // in scope 0 at $DIR/generator-drop-cleanup.rs:12:9: 12:14
-    let mut _5: ();                      // in scope 0 at $DIR/generator-drop-cleanup.rs:12:9: 12:14
-    let mut _6: ();                      // in scope 0 at $DIR/generator-drop-cleanup.rs:10:18: 10:18
-    let mut _7: ();                      // in scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
-    let mut _8: u32;                     // in scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
+    let mut _2: u32;                     // in scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
     scope 1 {
         debug _s => (((*_1) as variant#3).0: std::string::String); // in scope 1 at $DIR/generator-drop-cleanup.rs:11:13: 11:15
     }
 
     bb0: {
-        _8 = discriminant((*_1));        // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
-        switchInt(move _8) -> [0_u32: bb7, 3_u32: bb10, otherwise: bb11]; // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
+        _2 = discriminant((*_1));        // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
+        switchInt(move _2) -> [0_u32: bb3, 3_u32: bb4, otherwise: bb5]; // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
     }
 
     bb1: {
-        StorageDead(_5);                 // scope 1 at $DIR/generator-drop-cleanup.rs:12:13: 12:14
-        StorageDead(_4);                 // scope 1 at $DIR/generator-drop-cleanup.rs:12:14: 12:15
-        drop((((*_1) as variant#3).0: std::string::String)) -> [return: bb2, unwind: bb5]; // scope 0 at $DIR/generator-drop-cleanup.rs:13:5: 13:6
-    }
-
-    bb2: {
-        nop;                             // scope 0 at $DIR/generator-drop-cleanup.rs:13:5: 13:6
-        goto -> bb8;                     // scope 0 at $DIR/generator-drop-cleanup.rs:13:5: 13:6
-    }
-
-    bb3: {
         return;                          // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
     }
 
-    bb4 (cleanup): {
+    bb2 (cleanup): {
         resume;                          // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
     }
 
-    bb5 (cleanup): {
-        nop;                             // scope 0 at $DIR/generator-drop-cleanup.rs:13:5: 13:6
-        goto -> bb4;                     // scope 0 at $DIR/generator-drop-cleanup.rs:13:5: 13:6
-    }
-
-    bb6: {
+    bb3: {
         return;                          // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
     }
 
-    bb7: {
-        goto -> bb9;                     // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
-    }
-
-    bb8: {
-        goto -> bb3;                     // scope 0 at $DIR/generator-drop-cleanup.rs:13:5: 13:6
-    }
-
-    bb9: {
-        goto -> bb6;                     // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
-    }
-
-    bb10: {
-        StorageLive(_4);                 // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
-        StorageLive(_5);                 // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
-        goto -> bb1;                     // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
+    bb4: {
+        drop((((*_1) as variant#3).0: std::string::String)) -> [return: bb1, unwind: bb2]; // scope 0 at $DIR/generator-drop-cleanup.rs:13:5: 13:6
     }
 
-    bb11: {
+    bb5: {
         return;                          // scope 0 at $DIR/generator-drop-cleanup.rs:+0:15: +0:17
     }
 }