rustc_mir_transform/
add_call_guards.rs1use rustc_index::{Idx, IndexVec};
2use rustc_middle::mir::*;
3use rustc_middle::ty::TyCtxt;
4use tracing::debug;
5
6#[derive(PartialEq)]
7pub(super) enum AddCallGuards {
8 AllCallEdges,
9 CriticalCallEdges,
10}
11pub(super) use self::AddCallGuards::*;
12
13impl<'tcx> crate::MirPass<'tcx> for AddCallGuards {
34 fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
35 let mut pred_count = IndexVec::from_elem(0u8, &body.basic_blocks);
36 for (_, data) in body.basic_blocks.iter_enumerated() {
37 for succ in data.terminator().successors() {
38 pred_count[succ] = pred_count[succ].saturating_add(1);
39 }
40 }
41
42 let mut new_blocks = Vec::new();
44
45 let cur_len = body.basic_blocks.len();
46 let mut new_block = |source_info: SourceInfo, is_cleanup: bool, target: BasicBlock| {
47 let block = BasicBlockData::new(
48 Some(Terminator { source_info, kind: TerminatorKind::Goto { target } }),
49 is_cleanup,
50 );
51 let idx = cur_len + new_blocks.len();
52 new_blocks.push(block);
53 BasicBlock::new(idx)
54 };
55
56 for block in body.basic_blocks_mut() {
57 match block.terminator {
58 Some(Terminator {
59 kind: TerminatorKind::Call { target: Some(ref mut destination), unwind, .. },
60 source_info,
61 }) if pred_count[*destination] > 1
62 && (generates_invoke(unwind) || self == &AllCallEdges) =>
63 {
64 *destination = new_block(source_info, block.is_cleanup, *destination);
66 }
67 Some(Terminator {
68 kind:
69 TerminatorKind::InlineAsm {
70 asm_macro: InlineAsmMacro::Asm,
71 ref mut targets,
72 ref operands,
73 unwind,
74 ..
75 },
76 source_info,
77 }) if self == &CriticalCallEdges => {
78 let has_outputs = operands.iter().any(|op| {
79 matches!(op, InlineAsmOperand::InOut { .. } | InlineAsmOperand::Out { .. })
80 });
81 let has_labels =
82 operands.iter().any(|op| matches!(op, InlineAsmOperand::Label { .. }));
83 if has_outputs && (has_labels || generates_invoke(unwind)) {
84 for target in targets.iter_mut() {
85 if pred_count[*target] > 1 {
86 *target = new_block(source_info, block.is_cleanup, *target);
87 }
88 }
89 }
90 }
91 _ => {}
92 }
93 }
94
95 debug!("Broke {} N edges", new_blocks.len());
96
97 body.basic_blocks_mut().extend(new_blocks);
98 }
99
100 fn is_required(&self) -> bool {
101 true
102 }
103}
104
105fn generates_invoke(unwind: UnwindAction) -> bool {
107 match unwind {
108 UnwindAction::Continue | UnwindAction::Unreachable => false,
109 UnwindAction::Cleanup(_) | UnwindAction::Terminate(_) => true,
110 }
111}