Recreate the test cases for matches_reduce_branches.rs.

Author: dianqk

tests/mir-opt/matches_reduce_branches.match_i16_i8.MatchBranchSimplification.diff

@@ -0,0 +1,52 @@
+- // MIR for `match_sext_i8_i16` before MatchBranchSimplification
++ // MIR for `match_sext_i8_i16` after MatchBranchSimplification
+  
+  fn match_sext_i8_i16(_1: EnumAi8) -> i16 {
+      debug i => _1;
+      let mut _0: i16;
+      let mut _2: i8;
++     let mut _3: i8;
+  
+      bb0: {
+          _2 = discriminant(_1);
+-         switchInt(move _2) -> [128: bb3, 255: bb4, 0: bb5, 1: bb6, 127: bb2, otherwise: bb1];
+-     }
+- 
+-     bb1: {
+-         unreachable;
+-     }
+- 
+-     bb2: {
+-         _0 = const 127_i16;
+-         goto -> bb7;
+-     }
+- 
+-     bb3: {
+-         _0 = const -128_i16;
+-         goto -> bb7;
+-     }
+- 
+-     bb4: {
+-         _0 = const -1_i16;
+-         goto -> bb7;
+-     }
+- 
+-     bb5: {
+-         _0 = const 0_i16;
+-         goto -> bb7;
+-     }
+- 
+-     bb6: {
+-         _0 = const 1_i16;
+-         goto -> bb7;
+-     }
+- 
+-     bb7: {
++         StorageLive(_3);
++         _3 = move _2;
++         _0 = _3 as i16 (IntToInt);
++         StorageDead(_3);
+          return;
+      }
+  }
+  

tests/mir-opt/matches_reduce_branches.match_i8_i16.MatchBranchSimplification.diff

@@ -0,0 +1,47 @@
+- // MIR for `match_sext_i8_i16_failed` before MatchBranchSimplification
++ // MIR for `match_sext_i8_i16_failed` after MatchBranchSimplification
+  
+  fn match_sext_i8_i16_failed(_1: EnumAi8) -> i16 {
+      debug i => _1;
+      let mut _0: i16;
+      let mut _2: i8;
+  
+      bb0: {
+          _2 = discriminant(_1);
+          switchInt(move _2) -> [128: bb3, 255: bb4, 0: bb5, 1: bb6, 127: bb2, otherwise: bb1];
+      }
+  
+      bb1: {
+          unreachable;
+      }
+  
+      bb2: {
+          _0 = const 127_i16;
+          goto -> bb7;
+      }
+  
+      bb3: {
+          _0 = const -128_i16;
+          goto -> bb7;
+      }
+  
+      bb4: {
+          _0 = const 255_i16;
+          goto -> bb7;
+      }
+  
+      bb5: {
+          _0 = const 0_i16;
+          goto -> bb7;
+      }
+  
+      bb6: {
+          _0 = const 1_i16;
+          goto -> bb7;
+      }
+  
+      bb7: {
+          return;
+      }
+  }
+  

tests/mir-opt/matches_reduce_branches.match_i8_i16_failed.MatchBranchSimplification.diff

@@ -0,0 +1,52 @@
+- // MIR for `match_sext_i8_u16` before MatchBranchSimplification
++ // MIR for `match_sext_i8_u16` after MatchBranchSimplification
+  
+  fn match_sext_i8_u16(_1: EnumAi8) -> u16 {
+      debug i => _1;
+      let mut _0: u16;
+      let mut _2: i8;
++     let mut _3: i8;
+  
+      bb0: {
+          _2 = discriminant(_1);
+-         switchInt(move _2) -> [128: bb3, 255: bb4, 0: bb5, 1: bb6, 127: bb2, otherwise: bb1];
+-     }
+- 
+-     bb1: {
+-         unreachable;
+-     }
+- 
+-     bb2: {
+-         _0 = const 127_u16;
+-         goto -> bb7;
+-     }
+- 
+-     bb3: {
+-         _0 = const 65408_u16;
+-         goto -> bb7;
+-     }
+- 
+-     bb4: {
+-         _0 = const u16::MAX;
+-         goto -> bb7;
+-     }
+- 
+-     bb5: {
+-         _0 = const 0_u16;
+-         goto -> bb7;
+-     }
+- 
+-     bb6: {
+-         _0 = const 1_u16;
+-         goto -> bb7;
+-     }
+- 
+-     bb7: {
++         StorageLive(_3);
++         _3 = move _2;
++         _0 = _3 as u16 (IntToInt);
++         StorageDead(_3);
+          return;
+      }
+  }
+  

tests/mir-opt/matches_reduce_branches.match_i8_i16_failed_2.MatchBranchSimplification.diff

@@ -0,0 +1,47 @@
+- // MIR for `match_sext_i8_u16_failed` before MatchBranchSimplification
++ // MIR for `match_sext_i8_u16_failed` after MatchBranchSimplification
+  
+  fn match_sext_i8_u16_failed(_1: EnumAi8) -> u16 {
+      debug i => _1;
+      let mut _0: u16;
+      let mut _2: i8;
+  
+      bb0: {
+          _2 = discriminant(_1);
+          switchInt(move _2) -> [128: bb3, 255: bb4, 0: bb5, 1: bb6, 127: bb2, otherwise: bb1];
+      }
+  
+      bb1: {
+          unreachable;
+      }
+  
+      bb2: {
+          _0 = const 127_u16;
+          goto -> bb7;
+      }
+  
+      bb3: {
+          _0 = const 65408_u16;
+          goto -> bb7;
+      }
+  
+      bb4: {
+          _0 = const 255_u16;
+          goto -> bb7;
+      }
+  
+      bb5: {
+          _0 = const 0_u16;
+          goto -> bb7;
+      }
+  
+      bb6: {
+          _0 = const 1_u16;
+          goto -> bb7;
+      }
+  
+      bb7: {
+          return;
+      }
+  }
+