<commit_before>//! An analysis to determine which locals require allocas and
//! which do not.

use super::FunctionCx;
use crate::traits::*;
use rustc_data_structures::graph::dominators::Dominators;
use rustc_index::bit_set::BitSet;
use rustc_index::vec::{Idx, IndexVec};
use rustc_middle::mir::traversal;
use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
use rustc_middle::mir::{self, Location, TerminatorKind};
use rustc_middle::ty;
use rustc_middle::ty::layout::HasTyCtxt;
use rustc_target::abi::LayoutOf;

pub fn non_ssa_locals<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
    fx: &FunctionCx<'a, 'tcx, Bx>,
) -> BitSet<mir::Local> {
    let mir = fx.mir;
    let mut analyzer = LocalAnalyzer::new(fx);

    for (bb, data) in mir.basic_blocks().iter_enumerated() {
        analyzer.visit_basic_block_data(bb, data);
    }

    for (local, decl) in mir.local_decls.iter_enumerated() {
        let ty = fx.monomorphize(decl.ty);
        debug!("local {:?} has type `{}`", local, ty);
        let layout = fx.cx.spanned_layout_of(ty, decl.source_info.span);
        if fx.cx.is_backend_immediate(layout) {
            // These sorts of types are immediates that we can store
            // in an Value without an alloca.
        } else if fx.cx.is_backend_scalar_pair(layout) {
            // We allow pairs and uses of any of their 2 fields.
        } else {
            // These sorts of types require an alloca. Note that
            // is_llvm_immediate() may *still* be true, particularly
            // for newtypes, but we currently force some types
            // (e.g., structs) into an alloca unconditionally, just so
            // that we don't have to deal with having two pathways
            // (gep vs extractvalue etc).
            analyzer.not_ssa(local);
        }
    }

    analyzer.non_ssa_locals
}

struct LocalAnalyzer<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> {
    fx: &'mir FunctionCx<'a, 'tcx, Bx>,
    dominators: Dominators<mir::BasicBlock>,
    non_ssa_locals: BitSet<mir::Local>,
    // The location of the first visited direct assignment to each
    // local, or an invalid location (out of bounds `block` index).
    first_assignment: IndexVec<mir::Local, Location>,
}

impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
    fn new(fx: &'mir FunctionCx<'a, 'tcx, Bx>) -> Self {
        let invalid_location = mir::BasicBlock::new(fx.mir.basic_blocks().len()).start_location();
        let dominators = fx.mir.dominators();
        let mut analyzer = LocalAnalyzer {
            fx,
            dominators,
            non_ssa_locals: BitSet::new_empty(fx.mir.local_decls.len()),
            first_assignment: IndexVec::from_elem(invalid_location, &fx.mir.local_decls),
        };

        // Arguments get assigned to by means of the function being called
        for arg in fx.mir.args_iter() {
            analyzer.first_assignment[arg] = mir::START_BLOCK.start_location();
        }

        analyzer
    }

    fn first_assignment(&self, local: mir::Local) -> Option<Location> {
        let location = self.first_assignment[local];
        if location.block.index() < self.fx.mir.basic_blocks().len() {
            Some(location)
        } else {
            None
        }
    }

    fn not_ssa(&mut self, local: mir::Local) {
        debug!("marking {:?} as non-SSA", local);
        self.non_ssa_locals.insert(local);
    }

    fn assign(&mut self, local: mir::Local, location: Location) {
        if self.first_assignment(local).is_some() {
            self.not_ssa(local);
        } else {
            self.first_assignment[local] = location;
        }
    }

    fn process_place(
        &mut self,
        place_ref: &mir::PlaceRef<'tcx>,
        context: PlaceContext,
        location: Location,
    ) {
        let cx = self.fx.cx;

        if let Some((place_base, elem)) = place_ref.last_projection() {
            let mut base_context = if context.is_mutating_use() {
                PlaceContext::MutatingUse(MutatingUseContext::Projection)
            } else {
                PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
            };

            // Allow uses of projections that are ZSTs or from scalar fields.
            let is_consume = matches!(
                context,
                PlaceContext::NonMutatingUse(
                    NonMutatingUseContext::Copy | NonMutatingUseContext::Move,
                )
            );
            if is_consume {
                let base_ty = place_base.ty(self.fx.mir, cx.tcx());
                let base_ty = self.fx.monomorphize(base_ty);

                // ZSTs don't require any actual memory access.
                let elem_ty = base_ty.projection_ty(cx.tcx(), self.fx.monomorphize(elem)).ty;
                let span = self.fx.mir.local_decls[place_ref.local].source_info.span;
                if cx.spanned_layout_of(elem_ty, span).is_zst() {
                    return;
                }

                if let mir::ProjectionElem::Field(..) = elem {
                    let layout = cx.spanned_layout_of(base_ty.ty, span);
                    if cx.is_backend_immediate(layout) || cx.is_backend_scalar_pair(layout) {
                        // Recurse with the same context, instead of `Projection`,
                        // potentially stopping at non-operand projections,
                        // which would trigger `not_ssa` on locals.
                        base_context = context;
                    }
                }
            }

            if let mir::ProjectionElem::Deref = elem {
                // Deref projections typically only read the pointer.
                base_context = PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy);
            }

            self.process_place(&place_base, base_context, location);
            // HACK(eddyb) this emulates the old `visit_projection_elem`, this
            // entire `visit_place`-like `process_place` method should be rewritten,
            // now that we have moved to the "slice of projections" representation.
            if let mir::ProjectionElem::Index(local) = elem {
                self.visit_local(
                    &local,
                    PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
                    location,
                );
            }
        } else {
            // FIXME this is super_place code, is repeated here to avoid cloning place or changing
            // visit_place API
            let mut context = context;

            if !place_ref.projection.is_empty() {
                context = if context.is_mutating_use() {
                    PlaceContext::MutatingUse(MutatingUseContext::Projection)
                } else {
                    PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
                };
            }

            self.visit_local(&place_ref.local, context, location);
            self.visit_projection(*place_ref, context, location);
        }
    }
}

impl<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx>
    for LocalAnalyzer<'mir, 'a, 'tcx, Bx>
{
    fn visit_assign(
        &mut self,
        place: &mir::Place<'tcx>,
        rvalue: &mir::Rvalue<'tcx>,<commit_msg>Remove check for projections in a branch without any<commit_after>//! An analysis to determine which locals require allocas and
//! which do not.

use super::FunctionCx;
use crate::traits::*;
use rustc_data_structures::graph::dominators::Dominators;
use rustc_index::bit_set::BitSet;
use rustc_index::vec::{Idx, IndexVec};
use rustc_middle::mir::traversal;
use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
use rustc_middle::mir::{self, Location, TerminatorKind};
use rustc_middle::ty;
use rustc_middle::ty::layout::HasTyCtxt;
use rustc_target::abi::LayoutOf;

pub fn non_ssa_locals<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
    fx: &FunctionCx<'a, 'tcx, Bx>,
) -> BitSet<mir::Local> {
    let mir = fx.mir;
    let mut analyzer = LocalAnalyzer::new(fx);

    for (bb, data) in mir.basic_blocks().iter_enumerated() {
        analyzer.visit_basic_block_data(bb, data);
    }

    for (local, decl) in mir.local_decls.iter_enumerated() {
        let ty = fx.monomorphize(decl.ty);
        debug!("local {:?} has type `{}`", local, ty);
        let layout = fx.cx.spanned_layout_of(ty, decl.source_info.span);
        if fx.cx.is_backend_immediate(layout) {
            // These sorts of types are immediates that we can store
            // in an Value without an alloca.
        } else if fx.cx.is_backend_scalar_pair(layout) {
            // We allow pairs and uses of any of their 2 fields.
        } else {
            // These sorts of types require an alloca. Note that
            // is_llvm_immediate() may *still* be true, particularly
            // for newtypes, but we currently force some types
            // (e.g., structs) into an alloca unconditionally, just so
            // that we don't have to deal with having two pathways
            // (gep vs extractvalue etc).
            analyzer.not_ssa(local);
        }
    }

    analyzer.non_ssa_locals
}

struct LocalAnalyzer<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> {
    fx: &'mir FunctionCx<'a, 'tcx, Bx>,
    dominators: Dominators<mir::BasicBlock>,
    non_ssa_locals: BitSet<mir::Local>,
    // The location of the first visited direct assignment to each
    // local, or an invalid location (out of bounds `block` index).
    first_assignment: IndexVec<mir::Local, Location>,
}

impl<Bx: BuilderMethods<'a, 'tcx>> LocalAnalyzer<'mir, 'a, 'tcx, Bx> {
    fn new(fx: &'mir FunctionCx<'a, 'tcx, Bx>) -> Self {
        let invalid_location = mir::BasicBlock::new(fx.mir.basic_blocks().len()).start_location();
        let dominators = fx.mir.dominators();
        let mut analyzer = LocalAnalyzer {
            fx,
            dominators,
            non_ssa_locals: BitSet::new_empty(fx.mir.local_decls.len()),
            first_assignment: IndexVec::from_elem(invalid_location, &fx.mir.local_decls),
        };

        // Arguments get assigned to by means of the function being called
        for arg in fx.mir.args_iter() {
            analyzer.first_assignment[arg] = mir::START_BLOCK.start_location();
        }

        analyzer
    }

    fn first_assignment(&self, local: mir::Local) -> Option<Location> {
        let location = self.first_assignment[local];
        if location.block.index() < self.fx.mir.basic_blocks().len() {
            Some(location)
        } else {
            None
        }
    }

    fn not_ssa(&mut self, local: mir::Local) {
        debug!("marking {:?} as non-SSA", local);
        self.non_ssa_locals.insert(local);
    }

    fn assign(&mut self, local: mir::Local, location: Location) {
        if self.first_assignment(local).is_some() {
            self.not_ssa(local);
        } else {
            self.first_assignment[local] = location;
        }
    }

    fn process_place(
        &mut self,
        place_ref: &mir::PlaceRef<'tcx>,
        context: PlaceContext,
        location: Location,
    ) {
        let cx = self.fx.cx;

        if let Some((place_base, elem)) = place_ref.last_projection() {
            let mut base_context = if context.is_mutating_use() {
                PlaceContext::MutatingUse(MutatingUseContext::Projection)
            } else {
                PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection)
            };

            // Allow uses of projections that are ZSTs or from scalar fields.
            let is_consume = matches!(
                context,
                PlaceContext::NonMutatingUse(
                    NonMutatingUseContext::Copy | NonMutatingUseContext::Move,
                )
            );
            if is_consume {
                let base_ty = place_base.ty(self.fx.mir, cx.tcx());
                let base_ty = self.fx.monomorphize(base_ty);

                // ZSTs don't require any actual memory access.
                let elem_ty = base_ty.projection_ty(cx.tcx(), self.fx.monomorphize(elem)).ty;
                let span = self.fx.mir.local_decls[place_ref.local].source_info.span;
                if cx.spanned_layout_of(elem_ty, span).is_zst() {
                    return;
                }

                if let mir::ProjectionElem::Field(..) = elem {
                    let layout = cx.spanned_layout_of(base_ty.ty, span);
                    if cx.is_backend_immediate(layout) || cx.is_backend_scalar_pair(layout) {
                        // Recurse with the same context, instead of `Projection`,
                        // potentially stopping at non-operand projections,
                        // which would trigger `not_ssa` on locals.
                        base_context = context;
                    }
                }
            }

            if let mir::ProjectionElem::Deref = elem {
                // Deref projections typically only read the pointer.
                base_context = PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy);
            }

            self.process_place(&place_base, base_context, location);
            // HACK(eddyb) this emulates the old `visit_projection_elem`, this
            // entire `visit_place`-like `process_place` method should be rewritten,
            // now that we have moved to the "slice of projections" representation.
            if let mir::ProjectionElem::Index(local) = elem {
                self.visit_local(
                    &local,
                    PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy),
                    location,
                );
            }
        } else {
            self.visit_local(&place_ref.local, context, location);
        }
    }
}

impl<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx>
    for LocalAnalyzer<'mir, 'a, 'tcx, Bx>
{
    fn visit_assign(
        &mut self,
        place: &mir::Place<'tcx>,
        rvalue: &mir::Rvalue<'tcx>,
{'fraction_non_alphanumeric': 0.11437138573570357, 'fraction_numerical': 0.00014278574998215178, 'mean_word_length': 2.1422162404665768, 'pattern_counts': {'":': 0, '<': 49, '<?xml version=': 0, '>': 53, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
{'dir': 'git-commits-cleaned', 'id': '5517262', 'n_tokens_mistral': 4204, 'n_tokens_neox': 4125, 'n_words': 968}