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cranelift: add a new resumable_trapnz instruction;

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This is useful to have to allow resumable_trap to happen in loop
headers, for instance. This is the correct way to implement interrupt
checks in Spidermonkey, which are effectively resumable traps. Previous
implementation was using traps, which is wrong, since traps semantically
can't be resumed after.
This commit is contained in:
Benjamin Bouvier
2020-06-12 12:58:36 +02:00
parent 60d55a3483
commit dad56a2488
4 changed files with 36 additions and 12 deletions
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11
cranelift/codegen/src/isa/aarch64/lower_inst.rs
View File

@@ -1334,7 +1334,7 @@ pub(crate) fn lower_insn_to_regs<C: LowerCtx<I = Inst>>(
ctx.emit(Inst::Brk);
}
Opcode::Trap => {
Opcode::Trap | Opcode::ResumableTrap => {
let trap_info = (ctx.srcloc(insn), inst_trapcode(ctx.data(insn)).unwrap());
ctx.emit(Inst::Udf { trap_info })
}
@@ -1385,12 +1385,8 @@ pub(crate) fn lower_insn_to_regs<C: LowerCtx<I = Inst>>(
panic!("safepoint support not implemented!");
}
Opcode::Trapz | Opcode::Trapnz => {
panic!("trapz / trapnz should have been removed by legalization!");
}
Opcode::ResumableTrap => {
panic!("Resumable traps not supported");
Opcode::Trapz | Opcode::Trapnz | Opcode::ResumableTrapnz => {
panic!("trapz / trapnz / resumable_trapnz should have been removed by legalization!");
}
Opcode::FuncAddr => {
@@ -2277,6 +2273,7 @@ pub(crate) fn lower_branch<C: LowerCtx<I = Inst>>(
dest: BranchTarget::Label(targets[0]),
});
}
Opcode::BrTable => {
// Expand `br_table index, default, JT` to:
//

19
cranelift/codegen/src/legalizer/mod.rs
View File

@@ -214,6 +214,7 @@ pub fn simple_legalize(func: &mut ir::Function, cfg: &mut ControlFlowGraph, isa:
| ir::Opcode::TableAddr
| ir::Opcode::Trapnz
| ir::Opcode::Trapz
| ir::Opcode::ResumableTrapnz
| ir::Opcode::BandImm
| ir::Opcode::BorImm
| ir::Opcode::BxorImm
@@ -261,15 +262,15 @@ fn expand_cond_trap(
) {
// Parse the instruction.
let trapz;
let (arg, code) = match func.dfg[inst] {
let (arg, code, opcode) = match func.dfg[inst] {
ir::InstructionData::CondTrap { opcode, arg, code } => {
// We want to branch *over* an unconditional trap.
trapz = match opcode {
ir::Opcode::Trapz => true,
ir::Opcode::Trapnz => false,
ir::Opcode::Trapnz | ir::Opcode::ResumableTrapnz => false,
_ => panic!("Expected cond trap: {}", func.dfg.display_inst(inst, None)),
};
(arg, code)
(arg, code, opcode)
}
_ => panic!("Expected cond trap: {}", func.dfg.display_inst(inst, None)),
};
@@ -307,7 +308,17 @@ fn expand_cond_trap(
// Insert the new label and the unconditional trap terminator.
pos.insert_block(new_block_trap);
pos.ins().trap(code);
match opcode {
ir::Opcode::Trapz | ir::Opcode::Trapnz => {
pos.ins().trap(code);
}
ir::Opcode::ResumableTrapnz => {
pos.ins().resumable_trap(code);
pos.ins().jump(new_block_resume, &[]);
}
_ => unreachable!(),
}
// Insert the new label and resume the execution when the trap fails.
pos.insert_block(new_block_resume);