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[meta] Simplify handling of variable arguments in legalization;

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If a legalization contains varargs, it defers creating the binding for
the varargs, making the generated code easier to understand.
This commit is contained in:
Benjamin Bouvier
2019-10-01 17:21:52 +02:00
parent 687604d33a
commit d3ef80147b
1 changed files with 14 additions and 13 deletions
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27
cranelift/codegen/meta/src/gen_legalizer.rs
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@@ -44,6 +44,10 @@ fn unwrap_inst(
.args
.iter()
.enumerate()
.filter(|(arg_num, _)| {
// Variable args are specially handled after extracting args.
!inst.operands_in[*arg_num].is_varargs()
})
.map(|(arg_num, arg)| match &arg {
Expr::Var(var_index) => var_pool.get(*var_index).name.as_ref(),
Expr::Literal(_) => {
@@ -122,16 +126,9 @@ fn unwrap_inst(
} else if op.is_value() {
let n = inst.value_opnums.iter().position(|&i| i == op_num).unwrap();
fmtln!(fmt, "pos.func.dfg.resolve_aliases(args[{}]),", n);
} else if op.is_varargs() {
let n = inst.imm_opnums.iter().chain(inst.value_opnums.iter()).max().map(|n| n + 1).unwrap_or(0);
// We need to create a `Vec` here, as using a slice would result in a borrowck
// error later on.
fmtln!(fmt, "\
args.iter().skip({}).map(|&arg| pos.func.dfg.resolve_aliases(arg)).collect::<Vec<_>>(),\
", n);
} else {
// This is a value list argument.
assert!(iform.has_value_list);
// This is a value list argument or a varargs.
assert!(iform.has_value_list || op.is_varargs());
}
};
@@ -167,10 +164,14 @@ fn unwrap_inst(
let name = &var_pool
.get(apply.args[i].maybe_var().expect("vararg without name"))
.name;
// Above name is set to an `Vec` representing the varargs. However it is expected to be
// `&[Value]` below, so we borrow it.
fmtln!(fmt, "let {} = &{};", name, name);
let n = inst
.imm_opnums
.iter()
.chain(inst.value_opnums.iter())
.max()
.copied()
.unwrap_or(0);
fmtln!(fmt, "let {} = &Vec::from(&args[{}..]);", name, n);
}
}