Rewrite place workflow in rustc_codegen_llvm

Author: csmoe

src/librustc_codegen_llvm/mir/analyze.rs

@@ -15,6 +15,7 @@ use rustc_data_structures::bitvec::BitArray;
 use rustc_data_structures::graph::dominators::Dominators;
 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
 use rustc::mir::{self, Location, TerminatorKind};
+use rustc::mir::tcx::PlaceTy;
 use rustc::mir::visit::{Visitor, PlaceContext};
 use rustc::mir::traversal;
 use rustc::ty;
@@ -162,8 +163,9 @@ impl Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'll, 'tcx> {
                     location: Location) {
         let cx = self.fx.cx;
 
-        if !place.elems.is_empty() {
-            for (i, elem) in place.elems.iter().cloned().enumerate().rev() {
+        if !place.has_no_projection() {
+            let mut base_ty = place.base.ty(self.fx.mir);
+            for elem in place.elems.iter().cloned() {
                 debug!("visit_place(place={:?}, context={:?})", place, context);
 
                 // Allow uses of projections that are ZSTs or from scalar fields.
@@ -172,20 +174,15 @@ impl Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'll, 'tcx> {
                     _ => false
                 };
 
-                let base = place.elem_base(cx.tcx, i);
                 if is_consume {
-                    let base_ty = base.ty(self.fx.mir, cx.tcx);
-                    let base_ty = self.fx.monomorphize(&base_ty);
+                    base_ty = self.fx.monomorphize(&base_ty);
 
-                    // ZSTs don't require any actual memory access.
-                    let elem_ty = base_ty.projection_ty(cx.tcx, &elem).to_ty(cx.tcx);
-                    let elem_ty = self.fx.monomorphize(&elem_ty);
-                    if cx.layout_of(elem_ty).is_zst() {
+                    if cx.layout_of(base_ty).is_zst() {
                         return;
                     }
 
                     if let mir::ProjectionElem::Field(..) = elem {
-                        let layout = cx.layout_of(base_ty.to_ty(cx.tcx));
+                        let layout = cx.layout_of(base_ty);
                         if layout.is_llvm_immediate() || layout.is_llvm_scalar_pair() {
                             // Recurse with the same context, instead of `Projection`,
                             // potentially stopping at non-operand projections,
@@ -200,6 +197,7 @@ impl Visitor<'tcx> for LocalAnalyzer<'mir, 'a, 'll, 'tcx> {
                     context = PlaceContext::Copy;
                     continue;
                 }
+                base_ty = PlaceTy::from(base_ty).projection_ty(cx.tcx, &elem).to_ty(cx.tcx);
             }
         }
 

src/librustc_codegen_llvm/mir/operand.rs

@@ -313,7 +313,7 @@ impl FunctionCx<'a, 'll, 'tcx> {
         let mut result = None;
         // watch out for locals that do not have an
         // alloca; they are handled somewhat differently
-        if place.elems.is_empty() {
+        if place.has_no_projection() {
             if let mir::PlaceBase::Local(index) = place.base {
                 match self.locals[index] {
                     LocalRef::Operand(Some(o)) => {

src/librustc_codegen_llvm/mir/place.rs

@@ -417,10 +417,8 @@ impl FunctionCx<'a, 'll, 'tcx> {
         debug!("codegen_place(place={:?})", place);
 
         let cx = bx.cx;
-        let tcx = cx.tcx;
-
-        let mut result = match place.base {
-            mir::PlaceBase::Local(index) => {
+        if let mir::PlaceBase::Local(index) = place.base {
+            if place.has_no_projection() {
                 match self.locals[index] {
                     LocalRef::Place(place) => {
                         return place;
@@ -430,6 +428,9 @@ impl FunctionCx<'a, 'll, 'tcx> {
                     }
                 }
             }
+        };
+        let mut result = match place.base {
+            mir::PlaceBase::Local(_) => bug!(),
             mir::PlaceBase::Promoted(box (index, ty)) => {
                 let param_env = ty::ParamEnv::reveal_all();
                 let cid = mir::interpret::GlobalId {
@@ -462,7 +463,8 @@ impl FunctionCx<'a, 'll, 'tcx> {
             }
         };
 
-        if !place.elems.is_empty() {
+        if !place.has_no_projection() {
+            let tcx = cx.tcx;
             for (i, elem) in place.elems.iter().cloned().enumerate().rev() {
                 let base = place.elem_base(tcx, i);
                 result = match elem {

src/librustc_codegen_llvm/mir/rvalue.rs

@@ -518,7 +518,7 @@ impl FunctionCx<'a, 'll, 'tcx> {
     ) -> &'ll Value {
         // ZST are passed as operands and require special handling
         // because codegen_place() panics if Local is operand.
-        if place.elems.is_empty() {
+        if place.has_no_projection() {
             if let mir::PlaceBase::Local(index) = place.base {
                 if let LocalRef::Operand(Some(op)) = self.locals[index] {
                     if let ty::TyArray(_, n) = op.layout.ty.sty {