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machinst: fix the pinned reg hack;

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The pinned register hack didn't work because the GetPinnedReg is marked
as having side-effects, so that GVN wouldn't try to common it out.

This commit tweaks the function used during lowering to vcode, so that
the GetPinnedReg opcode is specially handled. It's a bit lame, but it
makes the hack work again.

Also, use_input needs to be a no-op for real registers.
This commit is contained in:
Benjamin Bouvier
2020-08-19 14:52:42 +02:00
parent efff43e769
commit ee76e01efc
2 changed files with 12 additions and 8 deletions
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8
cranelift/codegen/src/inst_predicates.rs
View File

@@ -41,9 +41,11 @@ pub fn has_side_effect(func: &Function, inst: Inst) -> bool {
trivially_has_side_effects(opcode) || is_load_with_defined_trapping(opcode, data)
}
/// Does the given instruction have any side-effect as per [has_side_effect], or else is a load?
pub fn has_side_effect_or_load(func: &Function, inst: Inst) -> bool {
has_side_effect(func, inst) || func.dfg[inst].opcode().can_load()
/// Does the given instruction have any side-effect as per [has_side_effect], or else is a load,
/// but not the get_pinned_reg opcode?
pub fn has_side_effect_or_load_not_get_pinned_reg(func: &Function, inst: Inst) -> bool {
let op = func.dfg[inst].opcode();
op != Opcode::GetPinnedReg && (has_side_effect(func, inst) || op.can_load())
}
/// Is the given instruction a constant value (`iconst`, `fconst`, `bconst`) that can be

12
cranelift/codegen/src/machinst/lower.rs
View File

@@ -4,7 +4,7 @@
use crate::entity::SecondaryMap;
use crate::fx::{FxHashMap, FxHashSet};
use crate::inst_predicates::{has_side_effect_or_load, is_constant_64bit};
use crate::inst_predicates::{has_side_effect_or_load_not_get_pinned_reg, is_constant_64bit};
use crate::ir::instructions::BranchInfo;
use crate::ir::types::I64;
use crate::ir::{
@@ -372,7 +372,7 @@ impl<'func, I: VCodeInst> Lower<'func, I> {
for bb in f.layout.blocks() {
cur_color += 1;
for inst in f.layout.block_insts(bb) {
let side_effect = has_side_effect_or_load(f, inst);
let side_effect = has_side_effect_or_load_not_get_pinned_reg(f, inst);
// Assign colors. A new color is chosen *after* any side-effecting instruction.
inst_colors[inst] = InstColor::new(cur_color);
@@ -800,14 +800,14 @@ impl<'func, I: VCodeInst> Lower<'func, I> {
debug!(" -> src inst {}", src_inst);
debug!(
" -> has side effect: {}",
has_side_effect_or_load(self.f, src_inst)
has_side_effect_or_load_not_get_pinned_reg(self.f, src_inst)
);
debug!(
" -> our color is {:?}, src inst is {:?}",
self.inst_color(at_inst),
self.inst_color(src_inst)
);
if !has_side_effect_or_load(self.f, src_inst)
if !has_side_effect_or_load_not_get_pinned_reg(self.f, src_inst)
|| self.inst_color(at_inst) == self.inst_color(src_inst)
{
Some((src_inst, result_idx))
@@ -989,7 +989,9 @@ impl<'func, I: VCodeInst> LowerCtx for Lower<'func, I> {
fn use_input_reg(&mut self, input: LowerInput) {
debug!("use_input_reg: vreg {:?} is needed", input.reg);
self.vreg_needed[input.reg.get_index()] = true;
if input.reg.is_virtual() {
self.vreg_needed[input.reg.get_index()] = true;
}
}
fn is_reg_needed(&self, ir_inst: Inst, reg: Reg) -> bool {