Add (and use) an analysis to determine which temps can forgo an alloca.
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Niko Matsakis
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544b06d455
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115
src/librustc_trans/trans/mir/analyze.rs
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115
src/librustc_trans/trans/mir/analyze.rs
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// 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
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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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} 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 getvalue 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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@ -10,7 +10,6 @@
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use libc::c_uint;
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use llvm::{self, ValueRef};
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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::tcx::LvalueTy;
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use trans::base;
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@ -79,7 +78,7 @@ pub fn trans_mir<'bcx, 'tcx>(bcx: Block<'bcx, 'tcx>) {
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// Analyze the temps to determine which must be lvalues
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// FIXME
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let lvalue_temps: FnvHashSet<usize> = (0..mir.temp_decls.len()).collect();
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let lvalue_temps = analyze::lvalue_temps(bcx, mir);
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// Allocate variable and temp allocas
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let vars = mir.var_decls.iter()
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@ -183,6 +182,7 @@ fn arg_value_refs<'bcx, 'tcx>(bcx: Block<'bcx, 'tcx>,
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.collect()
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}
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mod analyze;
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mod block;
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mod constant;
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mod lvalue;
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@ -16,8 +16,9 @@ use trans::build;
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use trans::common::Block;
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use trans::datum;
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use super::MirContext;
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use super::{MirContext, TempRef};
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#[derive(Copy, Clone)]
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pub struct OperandRef<'tcx> {
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// This will be "indirect" if `appropriate_rvalue_mode` returns
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// ByRef, and otherwise ByValue.
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@ -37,6 +38,25 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
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match *operand {
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mir::Operand::Consume(ref lvalue) => {
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// watch out for temporaries that do not have an
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// alloca; they are handled somewhat differently
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if let &mir::Lvalue::Temp(index) = lvalue {
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match self.temps[index as usize] {
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TempRef::Operand(Some(o)) => {
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return o;
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}
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TempRef::Operand(None) => {
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bcx.tcx().sess.bug(
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&format!("use of {:?} before def", lvalue));
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}
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TempRef::Lvalue(..) => {
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// use path below
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}
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}
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}
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// for most lvalues, to consume them we just load them
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// out from their home
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let tr_lvalue = self.trans_lvalue(bcx, lvalue);
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let ty = tr_lvalue.ty.to_ty(bcx.tcx());
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debug!("trans_operand: tr_lvalue={} @ {:?}",
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@ -80,7 +80,7 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
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}
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_ => {
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assert!(self.rvalue_creates_operand(rvalue));
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assert!(rvalue_creates_operand(rvalue));
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let (bcx, temp) = self.trans_rvalue_operand(bcx, rvalue);
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build::Store(bcx, temp.llval, lldest);
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bcx
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@ -88,32 +88,12 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
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}
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}
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pub fn rvalue_creates_operand(&self, rvalue: &mir::Rvalue<'tcx>) -> bool {
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match *rvalue {
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mir::Rvalue::Use(..) | // (*)
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mir::Rvalue::Ref(..) |
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mir::Rvalue::Len(..) |
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mir::Rvalue::Cast(..) | // (*)
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mir::Rvalue::BinaryOp(..) |
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mir::Rvalue::UnaryOp(..) |
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mir::Rvalue::Box(..) =>
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true,
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mir::Rvalue::Repeat(..) |
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mir::Rvalue::Aggregate(..) |
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mir::Rvalue::Slice { .. } |
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mir::Rvalue::InlineAsm(..) =>
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false,
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}
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// (*) this is only true if the type is suitable
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}
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pub fn trans_rvalue_operand(&mut self,
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bcx: Block<'bcx, 'tcx>,
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rvalue: &mir::Rvalue<'tcx>)
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-> (Block<'bcx, 'tcx>, OperandRef<'tcx>)
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{
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assert!(self.rvalue_creates_operand(rvalue), "cannot trans {:?} to operand", rvalue);
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assert!(rvalue_creates_operand(rvalue), "cannot trans {:?} to operand", rvalue);
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match *rvalue {
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mir::Rvalue::Use(ref operand) => {
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@ -300,3 +280,23 @@ impl<'bcx, 'tcx> MirContext<'bcx, 'tcx> {
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}
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}
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}
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pub fn rvalue_creates_operand<'tcx>(rvalue: &mir::Rvalue<'tcx>) -> bool {
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match *rvalue {
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mir::Rvalue::Use(..) | // (*)
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mir::Rvalue::Ref(..) |
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mir::Rvalue::Len(..) |
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mir::Rvalue::Cast(..) | // (*)
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mir::Rvalue::BinaryOp(..) |
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mir::Rvalue::UnaryOp(..) |
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mir::Rvalue::Box(..) =>
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true,
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mir::Rvalue::Repeat(..) |
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mir::Rvalue::Aggregate(..) |
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mir::Rvalue::Slice { .. } |
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mir::Rvalue::InlineAsm(..) =>
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false,
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}
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// (*) this is only true if the type is suitable
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}
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