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Refactor unwind generation in Cranelift.

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This commit makes the following changes to unwind information generation in
Cranelift:

* Remove frame layout change implementation in favor of processing the prologue
  and epilogue instructions when unwind information is requested.  This also
  means this work is no longer performed for Windows, which didn't utilize it.
  It also helps simplify the prologue and epilogue generation code.

* Remove the unwind sink implementation that required each unwind information
  to be represented in final form. For FDEs, this meant writing a
  complete frame table per function, which wastes 20 bytes or so for each
  function with duplicate CIEs.  This also enables Cranelift users to collect the
  unwind information and write it as a single frame table.

* For System V calling convention, the unwind information is no longer stored
  in code memory (it's only a requirement for Windows ABI to do so).  This allows
  for more compact code memory for modules with a lot of functions.

* Deletes some duplicate code relating to frame table generation.  Users can
  now simply use gimli to create a frame table from each function's unwind
  information.

Fixes #1181.
This commit is contained in:
Peter Huene
2020-03-30 19:48:02 -07:00
parent 7da6101732
commit f7e9f86ba9
42 changed files with 2678 additions and 3161 deletions
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23
cranelift/codegen/src/ir/function.rs
View File

@@ -10,13 +10,14 @@ use crate::ir::{
Block, ExtFuncData, FuncRef, GlobalValue, GlobalValueData, Heap, HeapData, Inst, JumpTable,
JumpTableData, Opcode, SigRef, StackSlot, StackSlotData, Table, TableData,
};
use crate::ir::{BlockOffsets, FrameLayout, InstEncodings, SourceLocs, StackSlots, ValueLocations};
use crate::ir::{BlockOffsets, InstEncodings, SourceLocs, StackSlots, ValueLocations};
use crate::ir::{DataFlowGraph, ExternalName, Layout, Signature};
use crate::ir::{JumpTableOffsets, JumpTables};
use crate::isa::{CallConv, EncInfo, Encoding, Legalize, TargetIsa};
use crate::regalloc::{EntryRegDiversions, RegDiversions};
use crate::value_label::ValueLabelsRanges;
use crate::write::write_function;
use alloc::vec::Vec;
use core::fmt;
/// A function.
@@ -87,15 +88,13 @@ pub struct Function {
/// Instruction that marks the end (inclusive) of the function's prologue.
///
/// This is used for some calling conventions to track the end of unwind information.
/// This is used for some ABIs to generate unwind information.
pub prologue_end: Option<Inst>,
/// Frame layout for the instructions.
/// The instructions that mark the start (inclusive) of an epilogue in the function.
///
/// The stack unwinding requires to have information about which registers and where they
/// are saved in the frame. This information is created during the prologue and epilogue
/// passes.
pub frame_layout: Option<FrameLayout>,
/// This is used for some ABIs to generate unwind information.
pub epilogues_start: Vec<Inst>,
}
impl Function {
@@ -119,7 +118,7 @@ impl Function {
jt_offsets: SecondaryMap::new(),
srclocs: SecondaryMap::new(),
prologue_end: None,
frame_layout: None,
epilogues_start: Vec::new(),
}
}
@@ -140,7 +139,7 @@ impl Function {
self.jt_offsets.clear();
self.srclocs.clear();
self.prologue_end = None;
self.frame_layout = None;
self.epilogues_start.clear();
}
/// Create a new empty, anonymous function with a Fast calling convention.
@@ -258,12 +257,6 @@ impl Function {
/// Starts collection of debug information.
pub fn collect_debug_info(&mut self) {
self.dfg.collect_debug_info();
self.collect_frame_layout_info();
}
/// Starts collection of frame layout information.
pub fn collect_frame_layout_info(&mut self) {
self.frame_layout = Some(FrameLayout::new());
}
/// Changes the destination of a jump or branch instruction.