116 lines
3.8 KiB
Rust
116 lines
3.8 KiB
Rust
// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! An analysis to determine which temporaries require allocas and
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//! which do not.
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use rustc_data_structures::fnv::FnvHashSet;
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use rustc::mir::repr as mir;
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use rustc::mir::visit::{Visitor, LvalueContext};
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use trans::common::{self, Block};
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use super::rvalue;
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pub fn lvalue_temps<'bcx,'tcx>(bcx: Block<'bcx,'tcx>,
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mir: &mir::Mir<'tcx>)
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-> FnvHashSet<usize> {
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let mut analyzer = TempAnalyzer::new();
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analyzer.visit_mir(mir);
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for (index, temp_decl) in mir.temp_decls.iter().enumerate() {
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let ty = bcx.monomorphize(&temp_decl.ty);
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debug!("temp {:?} has type {:?}", index, ty);
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if ty.is_scalar() ||
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ty.is_unique() ||
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ty.is_region_ptr() ||
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ty.is_simd()
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{
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// These sorts of types are immediates that we can store
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// in an ValueRef without an alloca.
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assert!(common::type_is_immediate(bcx.ccx(), ty) ||
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common::type_is_fat_ptr(bcx.tcx(), ty));
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} else {
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// These sorts of types require an alloca. Note that
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// type_is_immediate() may *still* be true, particularly
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// for newtypes, but we currently force some types
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// (e.g. structs) into an alloca unconditionally, just so
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// that we don't have to deal with having two pathways
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// (gep vs extractvalue etc).
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analyzer.mark_as_lvalue(index);
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}
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}
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analyzer.lvalue_temps
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}
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struct TempAnalyzer {
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lvalue_temps: FnvHashSet<usize>,
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}
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impl TempAnalyzer {
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fn new() -> TempAnalyzer {
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TempAnalyzer { lvalue_temps: FnvHashSet() }
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}
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fn mark_as_lvalue(&mut self, temp: usize) {
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debug!("marking temp {} as lvalue", temp);
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self.lvalue_temps.insert(temp);
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}
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}
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impl<'tcx> Visitor<'tcx> for TempAnalyzer {
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fn visit_assign(&mut self,
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block: mir::BasicBlock,
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lvalue: &mir::Lvalue<'tcx>,
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rvalue: &mir::Rvalue<'tcx>) {
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debug!("visit_assign(block={:?}, lvalue={:?}, rvalue={:?})", block, lvalue, rvalue);
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match *lvalue {
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mir::Lvalue::Temp(index) => {
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if !rvalue::rvalue_creates_operand(rvalue) {
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self.mark_as_lvalue(index as usize);
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}
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}
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_ => {
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self.visit_lvalue(lvalue, LvalueContext::Store);
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}
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}
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self.visit_rvalue(rvalue);
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}
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fn visit_lvalue(&mut self,
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lvalue: &mir::Lvalue<'tcx>,
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context: LvalueContext) {
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debug!("visit_lvalue(lvalue={:?}, context={:?})", lvalue, context);
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match *lvalue {
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mir::Lvalue::Temp(index) => {
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match context {
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LvalueContext::Consume => {
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}
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LvalueContext::Store |
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LvalueContext::Drop |
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LvalueContext::Inspect |
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LvalueContext::Borrow { .. } |
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LvalueContext::Slice { .. } |
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LvalueContext::Projection => {
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self.mark_as_lvalue(index as usize);
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}
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}
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}
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_ => {
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}
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}
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self.super_lvalue(lvalue, context);
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}
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}
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