77// option. This file may not be copied, modified, or distributed
88// except according to those terms.
99
10- //! This module converts MIR into Yorick TIR (Tracing IR). TIR is more suitable for the run-time
11- //! tracer: TIR (unlike MIR) is in SSA form (but it does preserve MIR's block structure) .
10+ //! This module converts MIR into Yorick TIR (Tracing IR).
11+ //! Note that we preserve the MIR block structure when lowering to TIR .
1212//!
1313//! Serialisation itself is performed by an external library: ykpack.
1414
@@ -30,8 +30,7 @@ use std::error::Error;
3030use std:: cell:: { Cell , RefCell } ;
3131use std:: mem:: size_of;
3232use rustc_data_structures:: bit_set:: BitSet ;
33- use rustc_data_structures:: indexed_vec:: { IndexVec , Idx } ;
34- use rustc_data_structures:: graph:: dominators:: DominatorFrontiers ;
33+ use rustc_data_structures:: indexed_vec:: IndexVec ;
3534use ykpack;
3635use ykpack:: LocalIndex as TirLocal ;
3736use rustc_data_structures:: fx:: FxHashSet ;
@@ -48,7 +47,7 @@ pub enum TirMode {
4847TextDump ( PathBuf ) ,
4948}
5049
51- /// A conversion context holds the state needed to perform the conversion to (pre-SSA) TIR.
50+ /// A conversion context holds the state needed to perform the TIR lowering .
5251struct ConvCx < ' a , ' tcx , ' gcx > {
5352 /// The compiler's god struct. Needed for queries etc.
5453tcx : & ' a TyCtxt < ' a , ' tcx , ' gcx > ,
@@ -106,11 +105,6 @@ impl<'a, 'tcx, 'gcx> ConvCx<'a, 'tcx, 'gcx> {
106105 } )
107106 }
108107
109- /// Finalise the conversion context, returning the definition sites and block defines mappings.
110- fn done ( self ) -> ( Vec < BitSet < BasicBlock > > , IndexVec < BasicBlock , FxHashSet < TirLocal > > ) {
111- ( self . def_sites . into_inner ( ) , self . block_defines . into_inner ( ) )
112- }
113-
114108 /// Add `bb` as a definition site of the TIR variable `var`.
115109fn push_def_site ( & self , bb : BasicBlock , var : TirLocal ) {
116110 let mut sites = self . def_sites . borrow_mut ( ) ;
@@ -165,12 +159,12 @@ fn do_generate_tir<'a, 'tcx, 'gcx>(
165159 // same between builds for the reproducible build tests to pass.
166160 let mut tir_path = exe_path. clone ( ) ;
167161 tir_path. set_extension ( TMP_EXT ) ;
168- let mut file = File :: create ( & tir_path) ?;
162+ let file = File :: create ( & tir_path) ?;
169163 ( tir_path, Some ( file) , None )
170164 } ,
171165 TirMode :: TextDump ( dump_path) => {
172166 // In text dump mode we just write lines to a file and we don't need an encoder.
173- let mut file = File :: create ( & dump_path) ?;
167+ let file = File :: create ( & dump_path) ?;
174168 ( dump_path. clone ( ) , None , Some ( file) )
175169 } ,
176170 } ;
@@ -187,19 +181,9 @@ fn do_generate_tir<'a, 'tcx, 'gcx>(
187181
188182 for def_id in sorted_def_ids {
189183 if tcx. is_mir_available ( * def_id) {
190- info ! ( "generating TIR for {:?}" , def_id) ;
191-
192184 let mir = tcx. optimized_mir ( * def_id) ;
193185 let ccx = ConvCx :: new ( tcx, mir) ;
194-
195- let mut pack = ( & ccx, def_id, tcx. optimized_mir ( * def_id) ) . to_pack ( ) ;
196- {
197- let ykpack:: Pack :: Mir ( ykpack:: Mir { ref mut blocks, ..} ) = pack;
198- let ( def_sites, block_defines) = ccx. done ( ) ;
199- insert_phis ( blocks, mir, def_sites, block_defines) ;
200- }
201-
202- // FIXME - rename variables with fresh SSA names.
186+ let pack = ( & ccx, def_id, tcx. optimized_mir ( * def_id) ) . to_pack ( ) ;
203187
204188 if let Some ( ref mut e) = enc {
205189 e. serialise ( pack) ?;
@@ -218,51 +202,6 @@ fn do_generate_tir<'a, 'tcx, 'gcx>(
218202 Ok ( tir_path)
219203}
220204
221- /// Insert PHI nodes into the initial pre-SSA TIR pack.
222- ///
223- /// Algorithm reference:
224- /// Bottom of p406 of 'Modern Compiler Implementation in Java (2nd ed.)' by Andrew Appel.
225- fn insert_phis ( blocks : & mut Vec < ykpack:: BasicBlock > , mir : & Mir ,
226- mut def_sites : Vec < BitSet < BasicBlock > > ,
227- a_orig : IndexVec < BasicBlock , FxHashSet < TirLocal > > ) {
228- let doms = mir. dominators ( ) ;
229- let df = DominatorFrontiers :: new ( mir, & doms) ;
230- let num_tir_vars = def_sites. len ( ) ;
231- let num_tir_blks = a_orig. len ( ) ;
232-
233- let mut a_phi: Vec < BitSet < TirLocal > > = Vec :: with_capacity ( num_tir_blks) ;
234- a_phi. resize ( num_tir_blks, BitSet :: new_empty ( num_tir_vars) ) ;
235-
236- // We don't need the elements of `def_sites` again past this point, so we can take them out
237- // of `def_sites` with a draining iterator and mutate in-place.
238- for ( a, mut w) in def_sites. drain ( ..) . enumerate ( ) {
239- while !w. is_empty ( ) {
240- let n = bitset_pop ( & mut w) ;
241- for y in df. frontier ( n) . iter ( ) {
242- let y_usize = y. index ( ) ;
243- // `def_sites` is guaranteed to only contain indices expressible by `u32`.
244- let a_u32 = a as u32 ;
245- if !a_phi[ y_usize] . contains ( a_u32) {
246- a_phi[ y_usize] . insert ( a_u32) ;
247- if !a_orig[ y] . contains ( & a_u32) {
248- // The assertion in `tir_var()` has already checked the cast is safe.
249- insert_phi ( & mut blocks[ y_usize] , a as u32 , mir. predecessors_for ( y) . len ( ) ) ;
250- w. insert ( y) ;
251- }
252- }
253- }
254- }
255- }
256- }
257-
258- fn insert_phi ( block : & mut ykpack:: BasicBlock , var : TirLocal , arity : usize ) {
259- let lhs = ykpack:: Place :: Local ( var) ;
260- let rhs_vars = ( 0 ..arity) . map ( |_| lhs. clone ( ) ) . collect ( ) ;
261- let rhs = ykpack:: Rvalue :: Phi ( rhs_vars) ;
262- block. stmts . insert ( 0 , ykpack:: Statement :: Assign ( lhs, rhs) ) ;
263- }
264-
265-
266205/// The trait for converting MIR data structures into a bytecode packs.
267206trait ToPack < T > {
268207 fn to_pack ( & mut self ) -> T ;
@@ -415,11 +354,3 @@ impl<'tcx> ToPack<ykpack::Rvalue> for (&ConvCx<'_, 'tcx, '_>, &Rvalue<'tcx>) {
415354 }
416355 }
417356}
418-
419- /// At the time of writing, you can't pop from a `BitSet`.
420- fn bitset_pop < T > ( s : & mut BitSet < T > ) -> T where T : Eq + Idx + Clone {
421- let e = s. iter ( ) . next ( ) . unwrap ( ) . clone ( ) ;
422- let removed = s. remove ( e) ;
423- debug_assert ! ( removed) ;
424- e
425- }
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