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//! Performs various peephole optimizations.
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use crate :: simplify:: simplify_duplicate_switch_targets;
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+ use rustc_ast:: attr;
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use rustc_middle:: mir:: * ;
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use rustc_middle:: ty:: layout;
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use rustc_middle:: ty:: layout:: ValidityRequirement ;
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use rustc_middle:: ty:: { self , GenericArgsRef , ParamEnv , Ty , TyCtxt } ;
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+ use rustc_span:: sym;
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use rustc_span:: symbol:: Symbol ;
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use rustc_target:: abi:: FieldIdx ;
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use rustc_target:: spec:: abi:: Abi ;
@@ -22,10 +24,17 @@ impl<'tcx> MirPass<'tcx> for InstSimplify {
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local_decls : & body. local_decls ,
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param_env : tcx. param_env_reveal_all_normalized ( body. source . def_id ( ) ) ,
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} ;
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+ // FIXME(#116171) Coverage related, also see `unreachable_prop.rs`.
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+ let rustc_ub_check = attr:: contains_name ( tcx. hir ( ) . krate_attrs ( ) , sym:: rustc_ub_check)
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+ || tcx. sess . instrument_coverage ( ) ;
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+ let debug_assertions = tcx. sess . opts . debug_assertions ;
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for block in body. basic_blocks . as_mut ( ) {
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for statement in block. statements . iter_mut ( ) {
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match statement. kind {
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StatementKind :: Assign ( box ( _place, ref mut rvalue) ) => {
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+ if !rustc_ub_check {
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+ ctx. simplify_ub_check ( & statement. source_info , rvalue, debug_assertions) ;
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+ }
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ctx. simplify_bool_cmp ( & statement. source_info , rvalue) ;
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ctx. simplify_ref_deref ( & statement. source_info , rvalue) ;
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ctx. simplify_len ( & statement. source_info , rvalue) ;
@@ -140,6 +149,24 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
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}
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}
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+ fn simplify_ub_check (
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+ & self ,
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+ source_info : & SourceInfo ,
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+ rvalue : & mut Rvalue < ' tcx > ,
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+ debug_assertions : bool ,
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+ ) {
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+ if let Rvalue :: NullaryOp ( ref null_op, _) = * rvalue {
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+ match null_op {
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+ NullOp :: SizeOf | NullOp :: AlignOf | NullOp :: OffsetOf ( _) => { }
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+ NullOp :: UbCheck ( _) => {
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+ let const_ = Const :: from_bool ( self . tcx , debug_assertions) ;
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+ let constant = ConstOperand { span : source_info. span , const_, user_ty : None } ;
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+ * rvalue = Rvalue :: Use ( Operand :: Constant ( Box :: new ( constant) ) ) ;
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+ }
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+ }
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+ }
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+ }
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+
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fn simplify_cast ( & self , rvalue : & mut Rvalue < ' tcx > ) {
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if let Rvalue :: Cast ( kind, operand, cast_ty) = rvalue {
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let operand_ty = operand. ty ( self . local_decls , self . tcx ) ;
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