22
33use crate :: MirPass ;
44use rustc_data_structures:: fx:: FxHashSet ;
5- use rustc_middle:: mir:: patch:: MirPatch ;
65use rustc_middle:: mir:: {
7- BasicBlock , BasicBlockData , BasicBlocks , Body , Local , Operand , Rvalue , StatementKind ,
8- TerminatorKind ,
6+ BasicBlockData , Body , Local , Operand , Rvalue , StatementKind , Terminator , TerminatorKind ,
97} ;
108use rustc_middle:: ty:: layout:: TyAndLayout ;
119use rustc_middle:: ty:: { Ty , TyCtxt } ;
@@ -79,8 +77,7 @@ impl<'tcx> MirPass<'tcx> for UninhabitedEnumBranching {
7977 fn run_pass ( & self , tcx : TyCtxt < ' tcx > , body : & mut Body < ' tcx > ) {
8078 trace ! ( "UninhabitedEnumBranching starting for {:?}" , body. source) ;
8179
82- let mut unreachable_targets = Vec :: new ( ) ;
83- let mut patch = MirPatch :: new ( body) ;
80+ let mut removable_switchs = Vec :: new ( ) ;
8481
8582 for ( bb, bb_data) in body. basic_blocks . iter_enumerated ( ) {
8683 trace ! ( "processing block {:?}" , bb) ;
@@ -95,73 +92,46 @@ impl<'tcx> MirPass<'tcx> for UninhabitedEnumBranching {
9592 tcx. param_env_reveal_all_normalized ( body. source . def_id ( ) ) . and ( discriminant_ty) ,
9693 ) ;
9794
98- let mut allowed_variants = if let Ok ( layout) = layout {
95+ let allowed_variants = if let Ok ( layout) = layout {
9996 variant_discriminants ( & layout, discriminant_ty, tcx)
100- } else if let Some ( variant_range) = discriminant_ty. variant_range ( tcx) {
101- variant_range
102- . map ( |variant| {
103- discriminant_ty. discriminant_for_variant ( tcx, variant) . unwrap ( ) . val
104- } )
105- . collect ( )
10697 } else {
10798 continue ;
10899 } ;
109100
110101 trace ! ( "allowed_variants = {:?}" , allowed_variants) ;
111102
112- unreachable_targets. clear ( ) ;
113- let TerminatorKind :: SwitchInt { targets, discr } = & bb_data. terminator ( ) . kind else {
114- bug ! ( )
115- } ;
103+ let terminator = bb_data. terminator ( ) ;
104+ let TerminatorKind :: SwitchInt { targets, .. } = & terminator. kind else { bug ! ( ) } ;
116105
106+ let mut reachable_count = 0 ;
117107 for ( index, ( val, _) ) in targets. iter ( ) . enumerate ( ) {
118- if !allowed_variants. remove ( & val) {
119- unreachable_targets. push ( index) ;
120- }
121- }
122- let otherwise_is_empty_unreachable =
123- body. basic_blocks [ targets. otherwise ( ) ] . is_empty_unreachable ( ) ;
124- // After resolving https://github.com/llvm/llvm-project/issues/78578,
125- // we can remove the limit on the number of successors.
126- fn check_successors ( basic_blocks : & BasicBlocks < ' _ > , bb : BasicBlock ) -> bool {
127- let mut successors = basic_blocks[ bb] . terminator ( ) . successors ( ) ;
128- let Some ( first_successor) = successors. next ( ) else { return true } ;
129- if successors. next ( ) . is_some ( ) {
130- return true ;
108+ if allowed_variants. contains ( & val) {
109+ reachable_count += 1 ;
110+ } else {
111+ removable_switchs. push ( ( bb, index) ) ;
131112 }
132- if let TerminatorKind :: SwitchInt { .. } =
133- & basic_blocks[ first_successor] . terminator ( ) . kind
134- {
135- return false ;
136- } ;
137- true
138113 }
139- let otherwise_is_last_variant = !otherwise_is_empty_unreachable
140- && allowed_variants. len ( ) == 1
141- && check_successors ( & body. basic_blocks , targets. otherwise ( ) ) ;
142- let replace_otherwise_to_unreachable = otherwise_is_last_variant
143- || !otherwise_is_empty_unreachable && allowed_variants. is_empty ( ) ;
144114
145- if unreachable_targets . is_empty ( ) && !replace_otherwise_to_unreachable {
146- continue ;
115+ if reachable_count == allowed_variants . len ( ) {
116+ removable_switchs . push ( ( bb , targets . iter ( ) . count ( ) ) ) ;
147117 }
118+ }
148119
149- let unreachable_block = patch. unreachable_no_cleanup_block ( ) ;
150- let mut targets = targets. clone ( ) ;
151- if replace_otherwise_to_unreachable {
152- if otherwise_is_last_variant {
153- #[ allow( rustc:: potential_query_instability) ]
154- let last_variant = * allowed_variants. iter ( ) . next ( ) . unwrap ( ) ;
155- targets. add_target ( last_variant, targets. otherwise ( ) ) ;
156- }
157- unreachable_targets. push ( targets. iter ( ) . count ( ) ) ;
158- }
159- for index in unreachable_targets. iter ( ) {
160- targets. all_targets_mut ( ) [ * index] = unreachable_block;
161- }
162- patch. patch_terminator ( bb, TerminatorKind :: SwitchInt { targets, discr : discr. clone ( ) } ) ;
120+ if removable_switchs. is_empty ( ) {
121+ return ;
163122 }
164123
165- patch. apply ( body) ;
124+ let new_block = BasicBlockData :: new ( Some ( Terminator {
125+ source_info : body. basic_blocks [ removable_switchs[ 0 ] . 0 ] . terminator ( ) . source_info ,
126+ kind : TerminatorKind :: Unreachable ,
127+ } ) ) ;
128+ let unreachable_block = body. basic_blocks . as_mut ( ) . push ( new_block) ;
129+
130+ for ( bb, index) in removable_switchs {
131+ let bb = & mut body. basic_blocks . as_mut ( ) [ bb] ;
132+ let terminator = bb. terminator_mut ( ) ;
133+ let TerminatorKind :: SwitchInt { targets, .. } = & mut terminator. kind else { bug ! ( ) } ;
134+ targets. all_targets_mut ( ) [ index] = unreachable_block;
135+ }
166136 }
167137}
0 commit comments