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Only generate a single trap to reduce code size and complexity in call_indirect

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This commit is contained in:
Jef
2019-01-18 16:59:29 +01:00
parent 2c8efa32b8
commit 26cb8de303
2 changed files with 49 additions and 43 deletions
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90
src/backend.rs
View File

@@ -239,6 +239,7 @@ impl CodeGenSession {
asm: &mut self.assembler,
func_starts: &self.func_starts,
has_memory: self.has_memory,
trap_label: None,
block_state: Default::default(),
}
}
@@ -525,6 +526,7 @@ pub struct Context<'a> {
func_starts: &'a Vec<(Option<AssemblyOffset>, DynamicLabel)>,
/// Each push and pop on the value stack increments or decrements this value by 1 respectively.
pub block_state: BlockState,
trap_label: Option<Label>,
has_memory: bool,
}
@@ -738,7 +740,6 @@ macro_rules! cmp_i64 {
#[must_use]
pub struct CallCleanup {
restore_registers: ArrayVec<[GPR; SCRATCH_REGS.len()]>,
stack_depth: i32,
}
@@ -2032,35 +2033,30 @@ impl Context<'_> {
// TODO: Use `ArrayVec`?
/// Saves volatile (i.e. caller-saved) registers before a function call, if they are used.
fn save_volatile(&mut self) -> ArrayVec<[GPR; SCRATCH_REGS.len()]> {
let mut out = ArrayVec::new();
for &reg in self.block_state.stack.iter().filter_map(|v| {
if let StackValue::Temp(r) = v {
Some(r)
} else {
None
}
}) {
{
fn save_volatile(&mut self) {
let mut reserved = 0;
for val in self.block_state.stack.iter_mut().rev() {
let reassign = if let StackValue::Temp(r) = val {
dynasm!(self.asm
; push Rq(reg)
; push Rq(*r)
);
out.push(reg);
true
} else {
false
};
if reassign {
*val = StackValue::Pop;
reserved += 1;
}
}
out
self.block_state.depth.reserve(reserved);
}
/// Write the arguments to the callee to the registers and the stack using the SystemV
/// calling convention.
fn pass_outgoing_args(
&mut self,
arity: u32,
return_arity: u32,
has_vmctx: bool,
) -> CallCleanup {
fn pass_outgoing_args(&mut self, arity: u32, has_vmctx: bool) -> CallCleanup {
let num_stack_args = (arity as usize).saturating_sub(ARGS_IN_GPRS.len()) as i32;
self.free_arg_registers(if has_vmctx { Some(0) } else { None });
@@ -2096,20 +2092,20 @@ impl Context<'_> {
self.pop_into(ValueLocation::Reg(*reg));
}
// We do this before doing `save_volatile`, since otherwise we'll trample the return value
// of the call when we pop back.
self.free_return_register(return_arity);
// TODO: This will stomp on stack arguments. We want to do this beforehand
// but then not actually change the recorded positions in the stack
// until `post_call_cleanup`.
self.save_volatile();
CallCleanup {
stack_depth: num_stack_args,
restore_registers: self.save_volatile(),
}
}
/// Frees up the stack space used for stack-passed arguments and restores the value
/// of volatile (i.e. caller-saved) registers to the state that they were in before
/// the call.
fn post_call_cleanup(&mut self, mut cleanup: CallCleanup) {
fn post_call_cleanup(&mut self, cleanup: CallCleanup) {
if cleanup.stack_depth > 0 {
let size = cleanup.stack_depth * WORD_SIZE as i32;
self.block_state.depth.free(cleanup.stack_depth as _);
@@ -2125,12 +2121,6 @@ impl Context<'_> {
*loc = ArgLoc::Stack(offset);
}
}
for reg in cleanup.restore_registers.drain(..).rev() {
dynasm!(self.asm
; pop Rq(reg)
);
}
}
fn push_function_return(&mut self, arity: u32) {
@@ -2154,13 +2144,15 @@ impl Context<'_> {
let vmctx_idx = self.block_state.locals.vmctx_index();
let (vmctx_reg, should_release_vmctx_reg) = self.into_reg(Value::Local(vmctx_idx));
let signature_matches = self.create_label();
let temp0 = self.block_state.regs.take_scratch_gpr();
let temp1 = self.block_state.regs.take_scratch_gpr();
let fail = self.trap_label().0;
// TODO: Consider generating a single trap function and jumping to that instead.
dynasm!(self.asm
; cmp Rq(callee), [Rq(vmctx_reg) + VmCtx::offset_of_funcs_len() as i32]
; jae >fail
; jae =>fail
; imul Rq(callee), Rq(callee), mem::size_of::<RuntimeFunc>() as i32
; mov Rq(temp0), [Rq(vmctx_reg) + VmCtx::offset_of_funcs_ptr() as i32]
; mov Rd(temp1), [
@@ -2169,13 +2161,9 @@ impl Context<'_> {
RuntimeFunc::offset_of_sig_hash() as i32
]
; cmp Rd(temp1), signature_hash as i32
; je =>signature_matches.0
; fail:
; jne =>fail
);
self.trap();
self.define_label(signature_matches);
self.block_state.regs.release_scratch_gpr(temp1);
// TODO: I believe that this can't cause quadratic runtime but I'm not
@@ -2186,7 +2174,7 @@ impl Context<'_> {
self.block_state
.stack
.insert(count - arg_arity as usize, vmctx);
let cleanup = self.pass_outgoing_args(arg_arity + 1, return_arity, true);
let cleanup = self.pass_outgoing_args(arg_arity + 1, true);
dynasm!(self.asm
; call QWORD [
@@ -2222,7 +2210,7 @@ impl Context<'_> {
self.block_state
.stack
.insert(count - arg_arity as usize, vmctx);
let cleanup = self.pass_outgoing_args(arg_arity + 1, return_arity, true);
let cleanup = self.pass_outgoing_args(arg_arity + 1, true);
let label = &self.func_starts[index as usize].1;
dynasm!(self.asm
@@ -2300,12 +2288,30 @@ impl Context<'_> {
dynasm!(self.asm
; ret
);
if let Some(l) = self.trap_label {
self.define_label(l);
dynasm!(self.asm
; ud2
);
}
}
pub fn trap(&mut self) {
let trap_label = self.trap_label();
dynasm!(self.asm
; ud2
; jmp =>trap_label.0
);
}
#[must_use]
fn trap_label(&mut self) -> Label {
if let Some(l) = self.trap_label {
return l;
}
self.trap_label = Some(self.create_label());
self.trap_label()
}
}

2
src/module.rs
View File

@@ -299,7 +299,7 @@ impl VmCtx {
}
pub fn offset_of_funcs_len() -> usize {
offset_of!(Self, table.ptr)
offset_of!(Self, table.len)
}
}