Auto merge of #29217 - nikomatsakis:mir-trans, r=dotdash

This branch implements a variant of trans that is based on MIR. It is very incomplete (intentionally), and had only the goal of laying out enough work to enable more incremental follow-on patches. Currently, only fns tagged with `#[rustc_mir]` use the new trans code. I plan to build up a meta-issue as well that tracks the various "not-yet-implemented" points. The only fn that has been tested so far is this amazingly complex "spike" fn:

```rust
#[rustc_mir]
fn sum(x: i32, y: i32) -> i32 {
    x + y
}
```

In general, the most interesting commit is the last one. There are some points on which I would like feedback from @rust-lang/compiler:

- I did not use `Datum`. Originally, I thought that maybe just a `ValueRef` would be enough but I wound up with two very simple structures, `LvalueRef` and `OperandRef`, that just package up a `ValueRef` and a type. Because of MIR's structure, you don't wind up mixing by-ref and by-value so much, and I tend to think that a thinner abstraction layer is better here, but I'm not sure.
- Related to the above, I expect that sooner or later we will analyze temps (and maybe variables too) to find those whose address is never taken and which are word-sized and which perhaps meet a few other criteria. For those, we'll probably want to avoid the alloca, just because it means prettier code.
- I generally tried to re-use data structures from elsewhere in trans, though I'm sure we can trim these down.
- I didn't do any debuginfo primarily because it seems to want node-ids and we have only spans. I haven't really read into that code so I don't know what's going on there.

r? @nrc

mk/crates.mk

@@ -103,7 +103,7 @@ DEPS_rustc_mir := rustc rustc_front syntax
 DEPS_rustc_resolve := rustc rustc_front log syntax
 DEPS_rustc_platform_intrinsics := rustc rustc_llvm
 DEPS_rustc_privacy := rustc rustc_front log syntax
-DEPS_rustc_trans := arena flate getopts graphviz libc rustc rustc_back \
+DEPS_rustc_trans := arena flate getopts graphviz libc rustc rustc_back rustc_mir \
                     log syntax serialize rustc_llvm rustc_front rustc_platform_intrinsics
 DEPS_rustc_typeck := rustc syntax rustc_front rustc_platform_intrinsics
 

src/librustc/middle/ty/context.rs

@@ -121,6 +121,13 @@ pub struct Tables<'tcx> {
     /// Records the type of each closure. The def ID is the ID of the
     /// expression defining the closure.
     pub closure_kinds: DefIdMap<ty::ClosureKind>,
+
+    /// For each fn, records the "liberated" types of its arguments
+    /// and return type. Liberated means that all bound regions
+    /// (including late-bound regions) are replaced with free
+    /// equivalents. This table is not used in trans (since regions
+    /// are erased there) and hence is not serialized to metadata.
+    pub liberated_fn_sigs: NodeMap<ty::FnSig<'tcx>>,
 }
 
 impl<'tcx> Tables<'tcx> {
@@ -133,6 +140,7 @@ impl<'tcx> Tables<'tcx> {
             upvar_capture_map: FnvHashMap(),
             closure_tys: DefIdMap(),
             closure_kinds: DefIdMap(),
+            liberated_fn_sigs: NodeMap(),
         }
     }
 

src/librustc/middle/ty/mod.rs

@@ -1731,6 +1731,13 @@ impl<'tcx, 'container> VariantDefData<'tcx, 'container> {
         self.fields.iter().find(|f| f.name == name)
     }
 
+    #[inline]
+    pub fn index_of_field_named(&self,
+                                name: ast::Name)
+                                -> Option<usize> {
+        self.fields.iter().position(|f| f.name == name)
+    }
+
     #[inline]
     pub fn field_named(&self, name: ast::Name) -> &FieldDefData<'tcx, 'container> {
         self.find_field_named(name).unwrap()

src/librustc_driver/driver.rs

@@ -11,6 +11,7 @@
 use rustc::front;
 use rustc::front::map as hir_map;
 use rustc_mir as mir;
+use rustc_mir::mir_map::MirMap;
 use rustc::session::Session;
 use rustc::session::config::{self, Input, OutputFilenames, OutputType};
 use rustc::session::search_paths::PathKind;
@@ -22,6 +23,7 @@ use rustc::middle::dependency_format;
 use rustc::middle;
 use rustc::plugin::registry::Registry;
 use rustc::plugin;
+use rustc::util::nodemap::NodeMap;
 use rustc::util::common::time;
 use rustc_borrowck as borrowck;
 use rustc_resolve as resolve;
@@ -146,7 +148,7 @@ pub fn compile_input(sess: Session,
                                     &arenas,
                                     &id,
                                     control.make_glob_map,
-                                    |tcx, analysis| {
+                                    |tcx, mir_map, analysis| {
 
             {
                 let state = CompileState::state_after_analysis(input,
@@ -170,7 +172,7 @@ pub fn compile_input(sess: Session,
                 println!("Pre-trans");
                 tcx.print_debug_stats();
             }
-            let trans = phase_4_translate_to_llvm(tcx, analysis);
+            let trans = phase_4_translate_to_llvm(tcx, &mir_map, analysis);
 
             if log_enabled!(::log::INFO) {
                 println!("Post-trans");
@@ -670,6 +672,7 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
                                                f: F)
                                                -> R
                                                where F: for<'a> FnOnce(&'a ty::ctxt<'tcx>,
+                                                                       MirMap<'tcx>,
                                                                        ty::CrateAnalysis) -> R
 {
     let time_passes = sess.time_passes();
@@ -751,18 +754,18 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
         time(time_passes, "match checking", ||
             middle::check_match::check_crate(tcx));
 
-        match tcx.sess.opts.unstable_features {
+        let mir_map = match tcx.sess.opts.unstable_features {
             UnstableFeatures::Disallow => {
                 // use this as a shorthand for beta/stable, and skip
                 // MIR construction there until known regressions are
                 // addressed
+                NodeMap()
             }
             UnstableFeatures::Allow | UnstableFeatures::Cheat => {
-                let _mir_map =
-                    time(time_passes, "MIR dump", ||
-                            mir::mir_map::build_mir_for_crate(tcx));
+                time(time_passes, "MIR dump", ||
+                     mir::mir_map::build_mir_for_crate(tcx))
             }
-        }
+        };
 
         time(time_passes, "liveness checking", ||
             middle::liveness::check_crate(tcx));
@@ -804,7 +807,7 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
         // The above three passes generate errors w/o aborting
         tcx.sess.abort_if_errors();
 
-        f(tcx, ty::CrateAnalysis {
+        f(tcx, mir_map, ty::CrateAnalysis {
             export_map: export_map,
             exported_items: exported_items,
             public_items: public_items,
@@ -817,16 +820,18 @@ pub fn phase_3_run_analysis_passes<'tcx, F, R>(sess: &'tcx Session,
 
 /// Run the translation phase to LLVM, after which the AST and analysis can
 /// be discarded.
-pub fn phase_4_translate_to_llvm(tcx: &ty::ctxt, analysis: ty::CrateAnalysis)
-                                 -> trans::CrateTranslation {
+pub fn phase_4_translate_to_llvm<'tcx>(tcx: &ty::ctxt<'tcx>,
+                                       mir_map: &MirMap<'tcx>,
+                                       analysis: ty::CrateAnalysis)
+                                       -> trans::CrateTranslation {
     let time_passes = tcx.sess.time_passes();
 
     time(time_passes, "resolving dependency formats", ||
          dependency_format::calculate(&tcx.sess));
 
     // Option dance to work around the lack of stack once closures.
     time(time_passes, "translation", move ||
-         trans::trans_crate(tcx, analysis))
+         trans::trans_crate(tcx, mir_map, analysis))
 }
 
 /// Run LLVM itself, producing a bitcode file, assembly file or object file

src/librustc_driver/pretty.rs

@@ -182,7 +182,7 @@ impl PpSourceMode {
                                                     arenas,
                                                     id,
                                                     resolve::MakeGlobMap::No,
-                                                    |tcx, _| {
+                                                    |tcx, _, _| {
                     let annotation = TypedAnnotation { tcx: tcx };
                     f(&annotation, payload, &ast_map.forest.krate)
                 })
@@ -782,7 +782,7 @@ pub fn pretty_print_input(sess: Session,
                                                         &arenas,
                                                         &id,
                                                         resolve::MakeGlobMap::No,
-                                                        |tcx, _| {
+                                                        |tcx, _, _| {
                         print_flowgraph(variants, tcx, code, mode, out)
                     })
                 }

src/librustc_mir/build/expr/as_rvalue.rs

@@ -71,7 +71,7 @@ impl<'a,'tcx> Builder<'a,'tcx> {
 
                 // schedule a shallow free of that memory, lest we unwind:
                 let extent = this.extent_of_innermost_scope().unwrap();
-                this.schedule_drop(expr_span, extent, DropKind::Shallow, &result, value_ty);
+                this.schedule_drop(expr_span, extent, DropKind::Free, &result, value_ty);
 
                 // initialize the box contents:
                 let contents = result.clone().deref();
@@ -149,16 +149,19 @@ impl<'a,'tcx> Builder<'a,'tcx> {
                 block.and(Rvalue::Aggregate(AggregateKind::Closure(closure_id, substs), upvars))
             }
             ExprKind::Adt { adt_def, variant_index, substs, fields, base } => { // see (*) above
-                // first process the set of fields
+                // first process the set of fields that were provided
+                // (evaluating them in order given by user)
                 let fields_map: FnvHashMap<_, _> =
                     fields.into_iter()
                           .map(|f| (f.name, unpack!(block = this.as_operand(block, f.expr))))
                           .collect();
 
-                let field_names = this.hir.fields(adt_def, variant_index);
-
+                // if base expression is given, evaluate it now
                 let base = base.map(|base| unpack!(block = this.as_lvalue(block, base)));
 
+                // get list of all fields that we will need
+                let field_names = this.hir.all_fields(adt_def, variant_index);
+
                 // for the actual values we use, take either the
                 // expr the user specified or, if they didn't
                 // specify something for this field name, create a

src/librustc_mir/build/expr/into.rs

@@ -211,10 +211,10 @@ impl<'a,'tcx> Builder<'a,'tcx> {
                 this.cfg.start_new_block().unit()
             }
             ExprKind::Call { fun, args } => {
-                let fun = unpack!(block = this.as_lvalue(block, fun));
+                let fun = unpack!(block = this.as_operand(block, fun));
                 let args: Vec<_> =
                     args.into_iter()
-                        .map(|arg| unpack!(block = this.as_lvalue(block, arg)))
+                        .map(|arg| unpack!(block = this.as_operand(block, arg)))
                         .collect();
                 let success = this.cfg.start_new_block();
                 let panic = this.diverge_cleanup();

src/librustc_mir/build/matches/test.rs

@@ -92,34 +92,36 @@ impl<'a,'tcx> Builder<'a,'tcx> {
                                           .collect();
                 self.cfg.terminate(block, Terminator::Switch {
                     discr: lvalue.clone(),
+                    adt_def: adt_def,
                     targets: target_blocks.clone()
                 });
                 target_blocks
             }
 
             TestKind::Eq { value, ty } => {
                 // call PartialEq::eq(discrim, constant)
-                let constant = self.push_literal(block, test.span, ty.clone(), value);
+                let constant = self.literal_operand(test.span, ty.clone(), value);
                 let item_ref = self.hir.partial_eq(ty);
-                self.call_comparison_fn(block, test.span, item_ref, lvalue.clone(), constant)
+                self.call_comparison_fn(block, test.span, item_ref,
+                                        Operand::Consume(lvalue.clone()), constant)
             }
 
             TestKind::Range { lo, hi, ty } => {
                 // Test `v` by computing `PartialOrd::le(lo, v) && PartialOrd::le(v, hi)`.
-                let lo = self.push_literal(block, test.span, ty.clone(), lo);
-                let hi = self.push_literal(block, test.span, ty.clone(), hi);
+                let lo = self.literal_operand(test.span, ty.clone(), lo);
+                let hi = self.literal_operand(test.span, ty.clone(), hi);
                 let item_ref = self.hir.partial_le(ty);
 
                 let lo_blocks = self.call_comparison_fn(block,
                                                         test.span,
                                                         item_ref.clone(),
                                                         lo,
-                                                        lvalue.clone());
+                                                        Operand::Consume(lvalue.clone()));
 
                 let hi_blocks = self.call_comparison_fn(lo_blocks[0],
                                                         test.span,
                                                         item_ref,
-                                                        lvalue.clone(),
+                                                        Operand::Consume(lvalue.clone()),
                                                         hi);
 
                 let failure = self.cfg.start_new_block();
@@ -164,14 +166,14 @@ impl<'a,'tcx> Builder<'a,'tcx> {
                           block: BasicBlock,
                           span: Span,
                           item_ref: ItemRef<'tcx>,
-                          lvalue1: Lvalue<'tcx>,
-                          lvalue2: Lvalue<'tcx>)
+                          lvalue1: Operand<'tcx>,
+                          lvalue2: Operand<'tcx>)
                           -> Vec<BasicBlock> {
         let target_blocks = vec![self.cfg.start_new_block(), self.cfg.start_new_block()];
 
         let bool_ty = self.hir.bool_ty();
         let eq_result = self.temp(bool_ty);
-        let func = self.push_item_ref(block, span, item_ref);
+        let func = self.item_ref_operand(span, item_ref);
         let call_blocks = [self.cfg.start_new_block(), self.diverge_cleanup()];
         self.cfg.terminate(block,
                            Terminator::Call {

src/librustc_mir/build/misc.rs

@@ -34,20 +34,17 @@ impl<'a,'tcx> Builder<'a,'tcx> {
         lvalue
     }
 
-    pub fn push_literal(&mut self,
-                        block: BasicBlock,
-                        span: Span,
-                        ty: Ty<'tcx>,
-                        literal: Literal<'tcx>)
-                        -> Lvalue<'tcx> {
-        let temp = self.temp(ty.clone());
+    pub fn literal_operand(&mut self,
+                           span: Span,
+                           ty: Ty<'tcx>,
+                           literal: Literal<'tcx>)
+                           -> Operand<'tcx> {
         let constant = Constant {
             span: span,
             ty: ty,
             literal: literal,
         };
-        self.cfg.push_assign_constant(block, span, &temp, constant);
-        temp
+        Operand::Constant(constant)
     }
 
     pub fn push_usize(&mut self, block: BasicBlock, span: Span, value: usize) -> Lvalue<'tcx> {
@@ -63,15 +60,14 @@ impl<'a,'tcx> Builder<'a,'tcx> {
         temp
     }
 
-    pub fn push_item_ref(&mut self,
-                         block: BasicBlock,
-                         span: Span,
-                         item_ref: ItemRef<'tcx>)
-                         -> Lvalue<'tcx> {
+    pub fn item_ref_operand(&mut self,
+                            span: Span,
+                            item_ref: ItemRef<'tcx>)
+                            -> Operand<'tcx> {
         let literal = Literal::Item {
             def_id: item_ref.def_id,
             substs: item_ref.substs,
         };
-        self.push_literal(block, span, item_ref.ty, literal)
+        self.literal_operand(span, item_ref.ty, literal)
     }
 }

src/librustc_mir/build/mod.rs

@@ -9,14 +9,14 @@
 // except according to those terms.
 
 use hair;
+use hair::cx::{Cx, PatNode};
 use rustc::middle::region::CodeExtent;
-use rustc::middle::ty::Ty;
+use rustc::middle::ty::{FnOutput, Ty};
 use rustc_data_structures::fnv::FnvHashMap;
 use rustc_front::hir;
 use repr::*;
 use syntax::ast;
 use syntax::codemap::Span;
-use tcx::{Cx, PatNode};
 
 struct Builder<'a, 'tcx: 'a> {
     hir: Cx<'a, 'tcx>,
@@ -75,13 +75,14 @@ macro_rules! unpack {
 ///////////////////////////////////////////////////////////////////////////
 // construct() -- the main entry point for building MIR for a function
 
-pub fn construct<'a, 'tcx>(mut hir: Cx<'a, 'tcx>,
-                           _span: Span,
-                           implicit_arguments: Vec<Ty<'tcx>>,
-                           explicit_arguments: Vec<(Ty<'tcx>, PatNode<'tcx>)>,
-                           argument_extent: CodeExtent,
-                           ast_block: &'tcx hir::Block)
-                           -> Mir<'tcx> {
+pub fn construct<'a,'tcx>(mut hir: Cx<'a,'tcx>,
+                          _span: Span,
+                          implicit_arguments: Vec<Ty<'tcx>>,
+                          explicit_arguments: Vec<(Ty<'tcx>, PatNode<'tcx>)>,
+                          argument_extent: CodeExtent,
+                          return_ty: FnOutput<'tcx>,
+                          ast_block: &'tcx hir::Block)
+                          -> Mir<'tcx> {
     let cfg = CFG { basic_blocks: vec![] };
 
     // it's handy to have a temporary of type `()` sometimes, so make
@@ -121,6 +122,7 @@ pub fn construct<'a, 'tcx>(mut hir: Cx<'a, 'tcx>,
         var_decls: builder.var_decls,
         arg_decls: arg_decls,
         temp_decls: builder.temp_decls,
+        return_ty: return_ty,
     }
 }