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Loosen the required order of values in a virtual register.

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Instead of requiring the values in a virtual register to be sorted
according to the domtree.rpo_cmp() order, just require any topological
ordering w.r.t. dominance.

The coalescer with stop using the RPO shortly.
This commit is contained in:
Jakob Stoklund Olesen
2017-12-12 16:16:01 -06:00
parent a825427786
commit 2473661d49
2 changed files with 23 additions and 25 deletions
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9
lib/cretonne/src/regalloc/virtregs.rs
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@@ -33,9 +33,6 @@ pub struct VirtRegs {
pool: ListPool<Value>,
/// The primary table of virtual registers.
///
/// The list of values ion a virtual register is kept sorted according to the dominator tree's
/// RPO of the value defs.
vregs: PrimaryMap<VirtReg, ValueList>,
/// Each value belongs to at most one virtual register.
@@ -65,8 +62,8 @@ impl VirtRegs {
self.value_vregs[value].into()
}
/// Get the list of values in `vreg`. The values are ordered according to `DomTree::rpo_cmp` of
/// their definition points.
/// Get the list of values in `vreg`.
/// The values are topologically ordered according dominance of their definition points.
pub fn values(&self, vreg: VirtReg) -> &[Value] {
self.vregs[vreg].as_slice(&self.pool)
}
@@ -103,7 +100,7 @@ impl VirtRegs {
/// If a value belongs to a virtual register, all of the values in that register must be
/// present.
///
/// The values are assumed to already be in RPO order.
/// The values are assumed to already be in topological order.
pub fn unify(&mut self, values: &[Value]) -> VirtReg {
// Start by clearing all virtual registers involved.
// Pick a virtual register to reuse (the smallest number) or allocate a new one.