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Overlap input and output stack slots

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This commit is contained in:
Gary Guo 2021-11-22 02:50:09 +00:00
parent 14aa039d30
commit fe3ba31860
1 changed files with 40 additions and 21 deletions
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61
src/inline_asm.rs
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@ -128,7 +128,6 @@ pub(crate) fn codegen_inline_asm<'tcx>(
let generated_asm = asm_gen.generate_asm_wrapper(&asm_name); let generated_asm = asm_gen.generate_asm_wrapper(&asm_name);
fx.cx.global_asm.push_str(&generated_asm); fx.cx.global_asm.push_str(&generated_asm);
// FIXME overlap input and output slots to save stack space
for (i, operand) in operands.iter().enumerate() { for (i, operand) in operands.iter().enumerate() {
match *operand { match *operand {
InlineAsmOperand::In { reg: _, ref value } => { InlineAsmOperand::In { reg: _, ref value } => {
@ -306,7 +305,7 @@ impl<'tcx> InlineAssemblyGenerator<'_, 'tcx> {
let mut slots_input = vec![None; self.operands.len()]; let mut slots_input = vec![None; self.operands.len()];
let mut slots_output = vec![None; self.operands.len()]; let mut slots_output = vec![None; self.operands.len()];
let mut new_slot = |reg_class: InlineAsmRegClass| { let new_slot_fn = |slot_size: &mut Size, reg_class: InlineAsmRegClass| {
let reg_size = reg_class let reg_size = reg_class
.supported_types(InlineAsmArch::X86_64) .supported_types(InlineAsmArch::X86_64)
.iter() .iter()
@ -314,11 +313,11 @@ impl<'tcx> InlineAssemblyGenerator<'_, 'tcx> {
.max() .max()
.unwrap(); .unwrap();
let align = rustc_target::abi::Align::from_bytes(reg_size.bytes()).unwrap(); let align = rustc_target::abi::Align::from_bytes(reg_size.bytes()).unwrap();
slot_size = slot_size.align_to(align); let offset = slot_size.align_to(align);
let offset = slot_size; *slot_size = offset + reg_size;
slot_size += reg_size;
offset offset
}; };
let mut new_slot = |x| new_slot_fn(&mut slot_size, x);
// Allocate stack slots for saving clobbered registers // Allocate stack slots for saving clobbered registers
let abi_clobber = let abi_clobber =
@ -346,30 +345,50 @@ impl<'tcx> InlineAssemblyGenerator<'_, 'tcx> {
} }
} }
// FIXME overlap input and output slots to save stack space // Allocate stack slots for inout
for (i, operand) in self.operands.iter().enumerate() { for (i, operand) in self.operands.iter().enumerate() {
match *operand { match *operand {
InlineAsmOperand::In { reg, .. } => { InlineAsmOperand::InOut { reg, out_place: Some(_), .. } => {
slots_input[i] = Some(new_slot(reg.reg_class()));
}
InlineAsmOperand::Out { reg, place, .. } => {
if place.is_some() {
slots_output[i] = Some(new_slot(reg.reg_class()));
}
}
InlineAsmOperand::InOut { reg, out_place, .. } => {
let slot = new_slot(reg.reg_class()); let slot = new_slot(reg.reg_class());
slots_input[i] = Some(slot); slots_input[i] = Some(slot);
if out_place.is_some() { slots_output[i] = Some(slot);
slots_output[i] = Some(slot);
}
} }
InlineAsmOperand::Const { value: _ } => (), _ => (),
InlineAsmOperand::SymFn { value: _ } => (),
InlineAsmOperand::SymStatic { def_id: _ } => (),
} }
} }
let slot_size_before_input = slot_size;
let mut new_slot = |x| new_slot_fn(&mut slot_size, x);
// Allocate stack slots for input
for (i, operand) in self.operands.iter().enumerate() {
match *operand {
InlineAsmOperand::In { reg, .. }
| InlineAsmOperand::InOut { reg, out_place: None, .. } => {
slots_input[i] = Some(new_slot(reg.reg_class()));
}
_ => (),
}
}
// Reset slot size to before input so that input and output operands can overlap
// and save some memory.
let slot_size_after_input = slot_size;
slot_size = slot_size_before_input;
let mut new_slot = |x| new_slot_fn(&mut slot_size, x);
// Allocate stack slots for output
for (i, operand) in self.operands.iter().enumerate() {
match *operand {
InlineAsmOperand::Out { reg, place: Some(_), .. } => {
slots_output[i] = Some(new_slot(reg.reg_class()));
}
_ => (),
}
}
slot_size = slot_size.max(slot_size_after_input);
self.stack_slots_clobber = slots_clobber; self.stack_slots_clobber = slots_clobber;
self.stack_slots_input = slots_input; self.stack_slots_input = slots_input;
self.stack_slots_output = slots_output; self.stack_slots_output = slots_output;