Add a more direct for not_equals optimization in InstCombine

The previous test's diff was changed by the const_goto pass such that the Ne(_1, false) pattern did not show anymore

Author: simonvandel

src/test/mir-opt/not_equal_false.opt.InstCombine.diff

@@ -1,38 +1,35 @@
 - // MIR for `opt` before InstCombine
 + // MIR for `opt` after InstCombine
 
-  fn opt(_1: Option<()>) -> bool {
+  fn opt(_1: bool) -> u32 {
       debug x => _1;                       // in scope 0 at $DIR/not_equal_false.rs:3:8: 3:9
-      let mut _0: bool;                    // return place in scope 0 at $DIR/not_equal_false.rs:3:26: 3:30
-      let mut _2: isize;                   // in scope 0 at $DIR/not_equal_false.rs:4:17: 4:21
-      let mut _3: isize;                   // in scope 0 at $DIR/not_equal_false.rs:4:38: 4:45
+      let mut _0: u32;                     // return place in scope 0 at $DIR/not_equal_false.rs:3:20: 3:23
+      let mut _2: bool;                    // in scope 0 at $DIR/not_equal_false.rs:4:8: 4:18
+      let mut _3: bool;                    // in scope 0 at $DIR/not_equal_false.rs:4:8: 4:9
 
       bb0: {
-          _2 = discriminant(_1);           // scope 0 at $DIR/not_equal_false.rs:4:17: 4:21
-          switchInt(move _2) -> [0_isize: bb3, otherwise: bb2]; // scope 0 at $DIR/not_equal_false.rs:4:17: 4:21
+          StorageLive(_2);                 // scope 0 at $DIR/not_equal_false.rs:4:8: 4:18
+          StorageLive(_3);                 // scope 0 at $DIR/not_equal_false.rs:4:8: 4:9
+          _3 = _1;                         // scope 0 at $DIR/not_equal_false.rs:4:8: 4:9
+-         _2 = Ne(move _3, const false);   // scope 0 at $DIR/not_equal_false.rs:4:8: 4:18
++         _2 = move _3;                    // scope 0 at $DIR/not_equal_false.rs:4:8: 4:18
+          StorageDead(_3);                 // scope 0 at $DIR/not_equal_false.rs:4:17: 4:18
+          switchInt(_2) -> [false: bb1, otherwise: bb2]; // scope 0 at $DIR/not_equal_false.rs:4:5: 4:35
       }
 
       bb1: {
-          _0 = const true;                 // scope 0 at $DIR/not_equal_false.rs:4:5: 4:46
-          return;                          // scope 0 at $DIR/not_equal_false.rs:4:5: 4:46
+          _0 = const 1_u32;                // scope 0 at $DIR/not_equal_false.rs:4:32: 4:33
+          goto -> bb3;                     // scope 0 at $DIR/not_equal_false.rs:4:5: 4:35
       }
 
       bb2: {
-          _3 = discriminant(_1);           // scope 0 at $DIR/not_equal_false.rs:4:38: 4:45
-          switchInt(move _3) -> [1_isize: bb5, otherwise: bb4]; // scope 0 at $DIR/not_equal_false.rs:4:38: 4:45
+          _0 = const 0_u32;                // scope 0 at $DIR/not_equal_false.rs:4:21: 4:22
+          goto -> bb3;                     // scope 0 at $DIR/not_equal_false.rs:4:5: 4:35
       }
 
       bb3: {
-          goto -> bb1;                     // scope 0 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
-      }
-  
-      bb4: {
-          _0 = const false;                // scope 0 at $DIR/not_equal_false.rs:4:5: 4:46
-          return;                          // scope 0 at $DIR/not_equal_false.rs:4:5: 4:46
-      }
-  
-      bb5: {
-          goto -> bb1;                     // scope 0 at $SRC_DIR/core/src/macros/mod.rs:LL:COL
+          StorageDead(_2);                 // scope 0 at $DIR/not_equal_false.rs:5:1: 5:2
+          return;                          // scope 0 at $DIR/not_equal_false.rs:5:2: 5:2
       }
   }
 

src/test/mir-opt/not_equal_false.rs

@@ -1,9 +1,9 @@
 // EMIT_MIR not_equal_false.opt.InstCombine.diff
 
-fn opt(x: Option<()>) -> bool {
-    matches!(x, None) || matches!(x, Some(_))
+fn opt(x: bool) -> u32 {
+    if x != false { 0 } else { 1 }
 }
 
 fn main() {
-    opt(None);
+    opt(false);
 }