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Avoid touching encodings in EncCursor if using a MachInst backend.

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`EncCursor` is a variant of `Cursor` that allows updating CLIF while
keeping its encodings up to date, given a particular ISA. However, new
(MachInst) backends don't use the encodings, and the `TargetIsaAdapter`
shim will panic if any encoding-related method is called. This PR avoids
those panics.

Fixes #1809.
This commit is contained in:
Chris Fallin
2020-06-03 17:01:17 -07:00
parent 5078e4eba2
commit 63a335b7d4
2 changed files with 499 additions and 9 deletions
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23
cranelift/codegen/src/cursor.rs
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@@ -794,15 +794,20 @@ impl<'c, 'f> ir::InstInserterBase<'c> for &'c mut EncCursor<'f> {
if !self.srcloc.is_default() {
self.func.srclocs[inst] = self.srcloc;
}
// Assign an encoding.
// XXX Is there a way to describe this error to the user?
#[cfg_attr(feature = "cargo-clippy", allow(clippy::match_wild_err_arm))]
match self
.isa
.encode(&self.func, &self.func.dfg[inst], ctrl_typevar)
{
Ok(e) => self.func.encodings[inst] = e,
Err(_) => panic!("can't encode {}", self.display_inst(inst)),
// Skip the encoding update if we're using a new (MachInst) backend; encodings come later,
// during lowering.
if self.isa.get_mach_backend().is_none() {
// Assign an encoding.
// XXX Is there a way to describe this error to the user?
#[cfg_attr(feature = "cargo-clippy", allow(clippy::match_wild_err_arm))]
match self
.isa
.encode(&self.func, &self.func.dfg[inst], ctrl_typevar)
{
Ok(e) => self.func.encodings[inst] = e,
Err(_) => panic!("can't encode {}", self.display_inst(inst)),
}
}
&mut self.func.dfg