559 lines
23 KiB
Rust
559 lines
23 KiB
Rust
//! Legalize ABI boundaries.
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//!
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//! This legalizer sub-module contains code for dealing with ABI boundaries:
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//!
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//! - Function arguments passed to the entry block.
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//! - Function arguments passed to call instructions.
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//! - Return values from call instructions.
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//! - Return values passed to return instructions.
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//!
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//! The ABI boundary legalization happens in two phases:
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//!
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//! 1. The `legalize_signatures` function rewrites all the preamble signatures with ABI information
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//! and possibly new argument types. It also rewrites the entry block arguments to match.
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//! 2. The `handle_call_abi` and `handle_return_abi` functions rewrite call and return instructions
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//! to match the new ABI signatures.
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//!
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//! Between the two phases, preamble signatures and call/return arguments don't match. This
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//! intermediate state doesn't type check.
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use abi::{legalize_abi_value, ValueConversion};
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use flowgraph::ControlFlowGraph;
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use ir::{Function, Cursor, DataFlowGraph, Inst, InstBuilder, Ebb, Type, Value, Signature, SigRef,
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ArgumentType, ArgumentPurpose};
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use ir::instructions::CallInfo;
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use isa::TargetIsa;
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use legalizer::split::{isplit, vsplit};
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/// Legalize all the function signatures in `func`.
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///
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/// This changes all signatures to be ABI-compliant with full `ArgumentLoc` annotations. It doesn't
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/// change the entry block arguments, calls, or return instructions, so this can leave the function
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/// in a state with type discrepancies.
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pub fn legalize_signatures(func: &mut Function, isa: &TargetIsa) {
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isa.legalize_signature(&mut func.signature, true);
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for sig in func.dfg.signatures.keys() {
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isa.legalize_signature(&mut func.dfg.signatures[sig], false);
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}
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if let Some(entry) = func.layout.entry_block() {
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legalize_entry_arguments(func, entry);
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}
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}
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/// Legalize the entry block arguments after `func`'s signature has been legalized.
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///
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/// The legalized signature may contain more arguments than the original signature, and the
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/// argument types have been changed. This function goes through the arguments to the entry EBB and
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/// replaces them with arguments of the right type for the ABI.
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///
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/// The original entry EBB arguments are computed from the new ABI arguments by code inserted at
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/// the top of the entry block.
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fn legalize_entry_arguments(func: &mut Function, entry: Ebb) {
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let mut has_sret = false;
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let mut has_link = false;
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// Insert position for argument conversion code.
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// We want to insert instructions before the first instruction in the entry block.
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// If the entry block is empty, append instructions to it instead.
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let mut pos = Cursor::new(&mut func.layout);
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pos.goto_top(entry);
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pos.next_inst();
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// Keep track of the argument types in the ABI-legalized signature.
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let abi_types = &func.signature.argument_types;
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let mut abi_arg = 0;
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// Process the EBB arguments one at a time, possibly replacing one argument with multiple new
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// ones. We do this by detaching the entry EBB arguments first.
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let ebb_args = func.dfg.detach_ebb_args(entry);
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let mut old_arg = 0;
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while let Some(arg) = ebb_args.get(old_arg, &func.dfg.value_lists) {
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old_arg += 1;
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let arg_type = func.dfg.value_type(arg);
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if arg_type == abi_types[abi_arg].value_type {
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// No value translation is necessary, this argument matches the ABI type.
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// Just use the original EBB argument value. This is the most common case.
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func.dfg.attach_ebb_arg(entry, arg);
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match abi_types[abi_arg].purpose {
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ArgumentPurpose::Normal => {}
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ArgumentPurpose::StructReturn => {
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assert!(!has_sret, "Multiple sret arguments found");
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has_sret = true;
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}
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_ => panic!("Unexpected special-purpose arg {}", abi_types[abi_arg]),
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}
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abi_arg += 1;
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} else {
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// Compute the value we want for `arg` from the legalized ABI arguments.
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let mut get_arg = |dfg: &mut DataFlowGraph, ty| {
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let abi_type = abi_types[abi_arg];
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assert_eq!(abi_type.purpose,
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ArgumentPurpose::Normal,
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"Can't legalize special-purpose argument");
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if ty == abi_type.value_type {
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abi_arg += 1;
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Ok(dfg.append_ebb_arg(entry, ty))
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} else {
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Err(abi_type)
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}
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};
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let converted =
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convert_from_abi(&mut func.dfg, &mut pos, arg_type, Some(arg), &mut get_arg);
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// The old `arg` is no longer an attached EBB argument, but there are probably still
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// uses of the value.
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assert_eq!(func.dfg.resolve_aliases(arg), converted);
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}
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}
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// The legalized signature may contain additional arguments representing special-purpose
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// registers.
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for &arg in &abi_types[abi_arg..] {
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match arg.purpose {
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// Any normal arguments should have been processed above.
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ArgumentPurpose::Normal => {
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panic!("Leftover arg: {}", arg);
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}
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// The callee-save arguments should not appear until after register allocation is
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// done.
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ArgumentPurpose::FramePointer |
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ArgumentPurpose::CalleeSaved => {
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panic!("Premature callee-saved arg {}", arg);
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}
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// These can be meaningfully added by `legalize_signature()`.
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ArgumentPurpose::Link => {
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assert!(!has_link, "Multiple link arguments found");
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has_link = true;
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}
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ArgumentPurpose::StructReturn => {
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assert!(!has_sret, "Multiple sret arguments found");
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has_sret = true;
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}
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}
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// Just create entry block values to match here. We will use them in `handle_return_abi()`
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// below.
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func.dfg.append_ebb_arg(entry, arg.value_type);
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}
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}
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/// Legalize the results returned from a call instruction to match the ABI signature.
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///
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/// The cursor `pos` points to a call instruction with at least one return value. The cursor will
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/// be left pointing after the instructions inserted to convert the return values.
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///
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/// This function is very similar to the `legalize_entry_arguments` function above.
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///
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/// Returns the possibly new instruction representing the call.
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fn legalize_inst_results<ResType>(dfg: &mut DataFlowGraph,
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pos: &mut Cursor,
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mut get_abi_type: ResType)
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-> Inst
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where ResType: FnMut(&DataFlowGraph, usize) -> ArgumentType
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{
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let call = pos.current_inst()
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.expect("Cursor must point to a call instruction");
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// We theoretically allow for call instructions that return a number of fixed results before
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// the call return values. In practice, it doesn't happen.
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let fixed_results = dfg[call].opcode().constraints().fixed_results();
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assert_eq!(fixed_results, 0, "Fixed results on calls not supported");
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let results = dfg.detach_results(call);
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let mut next_res = 0;
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let mut abi_res = 0;
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// Point immediately after the call.
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pos.next_inst();
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while let Some(res) = results.get(next_res, &dfg.value_lists) {
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next_res += 1;
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let res_type = dfg.value_type(res);
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if res_type == get_abi_type(dfg, abi_res).value_type {
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// No value translation is necessary, this result matches the ABI type.
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dfg.attach_result(call, res);
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abi_res += 1;
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} else {
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let mut get_res = |dfg: &mut DataFlowGraph, ty| {
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let abi_type = get_abi_type(dfg, abi_res);
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if ty == abi_type.value_type {
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let last_res = dfg.append_result(call, ty);
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abi_res += 1;
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Ok(last_res)
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} else {
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Err(abi_type)
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}
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};
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let v = convert_from_abi(dfg, pos, res_type, Some(res), &mut get_res);
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assert_eq!(dfg.resolve_aliases(res), v);
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}
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}
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call
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}
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/// Compute original value of type `ty` from the legalized ABI arguments.
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///
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/// The conversion is recursive, controlled by the `get_arg` closure which is called to retrieve an
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/// ABI argument. It returns:
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///
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/// - `Ok(arg)` if the requested type matches the next ABI argument.
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/// - `Err(arg_type)` if further conversions are needed from the ABI argument `arg_type`.
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///
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/// If the `into_result` value is provided, the converted result will be written into that value.
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fn convert_from_abi<GetArg>(dfg: &mut DataFlowGraph,
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pos: &mut Cursor,
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ty: Type,
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into_result: Option<Value>,
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get_arg: &mut GetArg)
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-> Value
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where GetArg: FnMut(&mut DataFlowGraph, Type) -> Result<Value, ArgumentType>
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{
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// Terminate the recursion when we get the desired type.
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let arg_type = match get_arg(dfg, ty) {
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Ok(v) => {
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debug_assert_eq!(dfg.value_type(v), ty);
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assert_eq!(into_result, None);
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return v;
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}
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Err(t) => t,
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};
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// Reconstruct how `ty` was legalized into the `arg_type` argument.
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let conversion = legalize_abi_value(ty, &arg_type);
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dbg!("convert_from_abi({}): {:?}", ty, conversion);
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// The conversion describes value to ABI argument. We implement the reverse conversion here.
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match conversion {
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// Construct a `ty` by concatenating two ABI integers.
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ValueConversion::IntSplit => {
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let abi_ty = ty.half_width().expect("Invalid type for conversion");
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let lo = convert_from_abi(dfg, pos, abi_ty, None, get_arg);
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let hi = convert_from_abi(dfg, pos, abi_ty, None, get_arg);
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dbg!("intsplit {}: {}, {}: {}",
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lo,
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dfg.value_type(lo),
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hi,
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dfg.value_type(hi));
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dfg.ins(pos).with_results([into_result]).iconcat(lo, hi)
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}
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// Construct a `ty` by concatenating two halves of a vector.
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ValueConversion::VectorSplit => {
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let abi_ty = ty.half_vector().expect("Invalid type for conversion");
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let lo = convert_from_abi(dfg, pos, abi_ty, None, get_arg);
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let hi = convert_from_abi(dfg, pos, abi_ty, None, get_arg);
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dfg.ins(pos).with_results([into_result]).vconcat(lo, hi)
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}
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// Construct a `ty` by bit-casting from an integer type.
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ValueConversion::IntBits => {
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assert!(!ty.is_int());
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let abi_ty = Type::int(ty.bits()).expect("Invalid type for conversion");
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let arg = convert_from_abi(dfg, pos, abi_ty, None, get_arg);
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dfg.ins(pos).with_results([into_result]).bitcast(ty, arg)
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}
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// ABI argument is a sign-extended version of the value we want.
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ValueConversion::Sext(abi_ty) => {
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let arg = convert_from_abi(dfg, pos, abi_ty, None, get_arg);
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// TODO: Currently, we don't take advantage of the ABI argument being sign-extended.
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// We could insert an `assert_sreduce` which would fold with a following `sextend` of
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// this value.
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dfg.ins(pos).with_results([into_result]).ireduce(ty, arg)
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}
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ValueConversion::Uext(abi_ty) => {
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let arg = convert_from_abi(dfg, pos, abi_ty, None, get_arg);
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// TODO: Currently, we don't take advantage of the ABI argument being sign-extended.
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// We could insert an `assert_ureduce` which would fold with a following `uextend` of
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// this value.
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dfg.ins(pos).with_results([into_result]).ireduce(ty, arg)
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}
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}
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}
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/// Convert `value` to match an ABI signature by inserting instructions at `pos`.
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///
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/// This may require expanding the value to multiple ABI arguments. The conversion process is
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/// recursive and controlled by the `put_arg` closure. When a candidate argument value is presented
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/// to the closure, it will perform one of two actions:
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///
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/// 1. If the suggested argument has an acceptable value type, consume it by adding it to the list
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/// of arguments and return `Ok(())`.
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/// 2. If the suggested argument doesn't have the right value type, don't change anything, but
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/// return the `Err(ArgumentType)` that is needed.
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///
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fn convert_to_abi<PutArg>(dfg: &mut DataFlowGraph,
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cfg: &ControlFlowGraph,
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pos: &mut Cursor,
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value: Value,
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put_arg: &mut PutArg)
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where PutArg: FnMut(&mut DataFlowGraph, Value) -> Result<(), ArgumentType>
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{
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// Start by invoking the closure to either terminate the recursion or get the argument type
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// we're trying to match.
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let arg_type = match put_arg(dfg, value) {
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Ok(_) => return,
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Err(t) => t,
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};
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let ty = dfg.value_type(value);
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match legalize_abi_value(ty, &arg_type) {
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ValueConversion::IntSplit => {
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let (lo, hi) = isplit(dfg, cfg, pos, value);
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convert_to_abi(dfg, cfg, pos, lo, put_arg);
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convert_to_abi(dfg, cfg, pos, hi, put_arg);
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}
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ValueConversion::VectorSplit => {
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let (lo, hi) = vsplit(dfg, cfg, pos, value);
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convert_to_abi(dfg, cfg, pos, lo, put_arg);
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convert_to_abi(dfg, cfg, pos, hi, put_arg);
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}
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ValueConversion::IntBits => {
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assert!(!ty.is_int());
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let abi_ty = Type::int(ty.bits()).expect("Invalid type for conversion");
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let arg = dfg.ins(pos).bitcast(abi_ty, value);
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convert_to_abi(dfg, cfg, pos, arg, put_arg);
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}
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ValueConversion::Sext(abi_ty) => {
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let arg = dfg.ins(pos).sextend(abi_ty, value);
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convert_to_abi(dfg, cfg, pos, arg, put_arg);
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}
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ValueConversion::Uext(abi_ty) => {
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let arg = dfg.ins(pos).uextend(abi_ty, value);
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convert_to_abi(dfg, cfg, pos, arg, put_arg);
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}
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}
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}
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/// Check if a sequence of arguments match a desired sequence of argument types.
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fn check_arg_types(dfg: &DataFlowGraph, args: &[Value], types: &[ArgumentType]) -> bool {
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let arg_types = args.iter().map(|&v| dfg.value_type(v));
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let sig_types = types.iter().map(|&at| at.value_type);
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arg_types.eq(sig_types)
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}
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/// Check if the arguments of the call `inst` match the signature.
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///
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/// Returns `Ok(())` if the signature matches and no changes are needed, or `Err(sig_ref)` if the
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/// signature doesn't match.
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fn check_call_signature(dfg: &DataFlowGraph, inst: Inst) -> Result<(), SigRef> {
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// Extract the signature and argument values.
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let (sig_ref, args) = match dfg[inst].analyze_call(&dfg.value_lists) {
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CallInfo::Direct(func, args) => (dfg.ext_funcs[func].signature, args),
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CallInfo::Indirect(sig_ref, args) => (sig_ref, args),
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CallInfo::NotACall => panic!("Expected call, got {:?}", dfg[inst]),
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};
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let sig = &dfg.signatures[sig_ref];
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if check_arg_types(dfg, args, &sig.argument_types[..]) &&
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check_arg_types(dfg, dfg.inst_results(inst), &sig.return_types[..]) {
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// All types check out.
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Ok(())
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} else {
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// Call types need fixing.
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Err(sig_ref)
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}
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}
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/// Check if the arguments of the return `inst` match the signature.
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fn check_return_signature(dfg: &DataFlowGraph, inst: Inst, sig: &Signature) -> bool {
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check_arg_types(dfg, dfg.inst_variable_args(inst), &sig.return_types)
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}
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/// Insert ABI conversion code for the arguments to the call or return instruction at `pos`.
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///
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/// - `abi_args` is the number of arguments that the ABI signature requires.
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/// - `get_abi_type` is a closure that can provide the desired `ArgumentType` for a given ABI
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/// argument number in `0..abi_args`.
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///
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fn legalize_inst_arguments<ArgType>(dfg: &mut DataFlowGraph,
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cfg: &ControlFlowGraph,
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pos: &mut Cursor,
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abi_args: usize,
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mut get_abi_type: ArgType)
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where ArgType: FnMut(&DataFlowGraph, usize) -> ArgumentType
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{
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let inst = pos.current_inst()
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.expect("Cursor must point to a call instruction");
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// Lift the value list out of the call instruction so we modify it.
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let mut vlist = dfg[inst]
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.take_value_list()
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.expect("Call must have a value list");
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// The value list contains all arguments to the instruction, including the callee on an
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// indirect call which isn't part of the call arguments that must match the ABI signature.
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// Figure out how many fixed values are at the front of the list. We won't touch those.
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let fixed_values = dfg[inst].opcode().constraints().fixed_value_arguments();
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let have_args = vlist.len(&dfg.value_lists) - fixed_values;
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// Grow the value list to the right size and shift all the existing arguments to the right.
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// This lets us write the new argument values into the list without overwriting the old
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// arguments.
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//
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// Before:
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//
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// <--> fixed_values
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// <-----------> have_args
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// [FFFFOOOOOOOOOOOOO]
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//
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// After grow_at():
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//
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// <--> fixed_values
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// <-----------> have_args
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// <------------------> abi_args
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// [FFFF-------OOOOOOOOOOOOO]
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// ^
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// old_arg_offset
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//
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// After writing the new arguments:
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//
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// <--> fixed_values
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// <------------------> abi_args
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// [FFFFNNNNNNNNNNNNNNNNNNNN]
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//
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vlist.grow_at(fixed_values, abi_args - have_args, &mut dfg.value_lists);
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let old_arg_offset = fixed_values + abi_args - have_args;
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let mut abi_arg = 0;
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for old_arg in 0..have_args {
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let old_value = vlist
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.get(old_arg_offset + old_arg, &dfg.value_lists)
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.unwrap();
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let mut put_arg = |dfg: &mut DataFlowGraph, arg| {
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let abi_type = get_abi_type(dfg, abi_arg);
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if dfg.value_type(arg) == abi_type.value_type {
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// This is the argument type we need.
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vlist.as_mut_slice(&mut dfg.value_lists)[fixed_values + abi_arg] = arg;
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abi_arg += 1;
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Ok(())
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} else {
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Err(abi_type)
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}
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};
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convert_to_abi(dfg, cfg, pos, old_value, &mut put_arg);
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}
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// Put the modified value list back.
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dfg[inst].put_value_list(vlist);
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}
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/// Insert ABI conversion code before and after the call instruction at `pos`.
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///
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/// Instructions inserted before the call will compute the appropriate ABI values for the
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/// callee's new ABI-legalized signature. The function call arguments are rewritten in place to
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/// match the new signature.
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///
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/// Instructions will be inserted after the call to convert returned ABI values back to the
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/// original return values. The call's result values will be adapted to match the new signature.
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|
///
|
|
/// Returns `true` if any instructions were inserted.
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|
pub fn handle_call_abi(dfg: &mut DataFlowGraph, cfg: &ControlFlowGraph, pos: &mut Cursor) -> bool {
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|
let mut inst = pos.current_inst()
|
|
.expect("Cursor must point to a call instruction");
|
|
|
|
// Start by checking if the argument types already match the signature.
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|
let sig_ref = match check_call_signature(dfg, inst) {
|
|
Ok(_) => return false,
|
|
Err(s) => s,
|
|
};
|
|
|
|
// OK, we need to fix the call arguments to match the ABI signature.
|
|
let abi_args = dfg.signatures[sig_ref].argument_types.len();
|
|
legalize_inst_arguments(dfg,
|
|
cfg,
|
|
pos,
|
|
abi_args,
|
|
|dfg, abi_arg| dfg.signatures[sig_ref].argument_types[abi_arg]);
|
|
|
|
if !dfg.signatures[sig_ref].return_types.is_empty() {
|
|
inst = legalize_inst_results(dfg,
|
|
pos,
|
|
|dfg, abi_res| dfg.signatures[sig_ref].return_types[abi_res]);
|
|
}
|
|
|
|
debug_assert!(check_call_signature(dfg, inst).is_ok(),
|
|
"Signature still wrong: {}, {}{}",
|
|
dfg.display_inst(inst),
|
|
sig_ref,
|
|
dfg.signatures[sig_ref]);
|
|
|
|
// Yes, we changed stuff.
|
|
true
|
|
}
|
|
|
|
/// Insert ABI conversion code before and after the return instruction at `pos`.
|
|
///
|
|
/// Return `true` if any instructions were inserted.
|
|
pub fn handle_return_abi(dfg: &mut DataFlowGraph,
|
|
cfg: &ControlFlowGraph,
|
|
pos: &mut Cursor,
|
|
sig: &Signature)
|
|
-> bool {
|
|
let inst = pos.current_inst()
|
|
.expect("Cursor must point to a return instruction");
|
|
|
|
// Check if the returned types already match the signature.
|
|
if check_return_signature(dfg, inst, sig) {
|
|
return false;
|
|
}
|
|
|
|
// Count the special-purpose return values (`link` and `sret`) that were appended to the
|
|
// legalized signature.
|
|
let special_args = sig.return_types
|
|
.iter()
|
|
.rev()
|
|
.take_while(|&rt| {
|
|
rt.purpose == ArgumentPurpose::Link ||
|
|
rt.purpose == ArgumentPurpose::StructReturn
|
|
})
|
|
.count();
|
|
|
|
let abi_args = sig.return_types.len() - special_args;
|
|
legalize_inst_arguments(dfg,
|
|
cfg,
|
|
pos,
|
|
abi_args,
|
|
|_, abi_arg| sig.return_types[abi_arg]);
|
|
assert_eq!(dfg.inst_variable_args(inst).len(), abi_args);
|
|
|
|
// Append special return arguments for any `sret` and `link` return values added to the
|
|
// legalized signature. These values should simply be propagated from the entry block
|
|
// arguments.
|
|
if special_args > 0 {
|
|
dbg!("Adding {} special-purpose arguments to {}",
|
|
special_args,
|
|
dfg.display_inst(inst));
|
|
let mut vlist = dfg[inst].take_value_list().unwrap();
|
|
for arg in &sig.return_types[abi_args..] {
|
|
match arg.purpose {
|
|
ArgumentPurpose::Link |
|
|
ArgumentPurpose::StructReturn => {}
|
|
ArgumentPurpose::Normal => panic!("unexpected return value {}", arg),
|
|
_ => panic!("Unsupported special purpose return value {}", arg),
|
|
}
|
|
// A `link` or `sret` return value can only appear in a signature that has a unique
|
|
// matching argument. They are appended at the end, so search the signature from the
|
|
// end.
|
|
let idx = sig.argument_types
|
|
.iter()
|
|
.rposition(|t| t.purpose == arg.purpose)
|
|
.expect("No matching special purpose argument.");
|
|
// Get the corresponding entry block value and add it to the return instruction's
|
|
// arguments.
|
|
let val = dfg.ebb_args(pos.layout.entry_block().unwrap())[idx];
|
|
debug_assert_eq!(dfg.value_type(val), arg.value_type);
|
|
vlist.push(val, &mut dfg.value_lists);
|
|
}
|
|
dfg[inst].put_value_list(vlist);
|
|
}
|
|
|
|
debug_assert!(check_return_signature(dfg, inst, sig),
|
|
"Signature still wrong: {} / signature {}",
|
|
dfg.display_inst(inst),
|
|
sig);
|
|
|
|
// Yes, we changed stuff.
|
|
true
|
|
}
|