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Enforce encodings for instructions with side effects.

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We allow ghost instructions to exist if they have no side effects.
Instructions that affect control flow or that have other side effects
must be encoded.

Teach the IL verifier to enforce this. Once any instruction has an
encoding, all instructions with side effects must have an encoding.
This commit is contained in:
Jakob Stoklund Olesen
2017-07-12 09:29:48 -07:00
parent 6ee432329d
commit 24b53efc9d
2 changed files with 61 additions and 21 deletions
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2
filetests/regalloc/coalesce.cton
View File

@@ -59,7 +59,7 @@ ebb0(v0: i32):
brnz v0, ebb1(v0)
v1 = iadd_imm v0, 7
; v1 and v0 interfere here:
trapnz v0
v2 = iadd_imm v0, 8
; check: $(cp1=$V) = copy $v1
; not: copy
; check: jump $ebb1($cp1)

80
lib/cretonne/src/verifier/mod.rs
View File

@@ -666,30 +666,70 @@ impl<'a> Verifier<'a> {
/// If the verifier has been set up with an ISA, make sure that the recorded encoding for the
/// instruction (if any) matches how the ISA would encode it.
fn verify_encoding(&self, inst: Inst) -> Result {
if let Some(isa) = self.isa {
let encoding = self.func.encodings.get_or_default(inst);
if encoding.is_legal() {
let verify_encoding =
isa.encode(&self.func.dfg,
&self.func.dfg[inst],
self.func.dfg.ctrl_typevar(inst));
match verify_encoding {
Ok(verify_encoding) => {
if verify_encoding != encoding {
return err!(inst,
"Instruction re-encoding {} doesn't match {}",
isa.encoding_info().display(verify_encoding),
isa.encoding_info().display(encoding));
}
}
Err(e) => {
// When the encodings table is empty, we don't require any instructions to be encoded.
//
// Once some instructions are encoded, we require all side-effecting instructions to have a
// legal encoding.
if self.func.encodings.is_empty() {
return Ok(());
}
let isa = match self.isa {
Some(isa) => isa,
None => return Ok(()),
};
let encoding = self.func.encodings.get_or_default(inst);
if encoding.is_legal() {
let verify_encoding =
isa.encode(&self.func.dfg,
&self.func.dfg[inst],
self.func.dfg.ctrl_typevar(inst));
match verify_encoding {
Ok(verify_encoding) => {
if verify_encoding != encoding {
return err!(inst,
"Instruction failed to re-encode {}: {:?}",
isa.encoding_info().display(encoding),
e)
"Instruction re-encoding {} doesn't match {}",
isa.encoding_info().display(verify_encoding),
isa.encoding_info().display(encoding));
}
}
Err(e) => {
return err!(inst,
"Instruction failed to re-encode {}: {:?}",
isa.encoding_info().display(encoding),
e)
}
}
return Ok(());
}
// Instruction is not encoded, so it is a ghost instruction.
// Instructions with side effects are not allowed to be ghost instructions.
let opcode = self.func.dfg[inst].opcode();
if opcode.is_branch() {
return err!(inst, "Branch must have an encoding");
}
if opcode.is_call() {
return err!(inst, "Call must have an encoding");
}
if opcode.is_return() {
return err!(inst, "Return must have an encoding");
}
if opcode.can_store() {
return err!(inst, "Store must have an encoding");
}
if opcode.can_trap() {
return err!(inst, "Trapping instruction must have an encoding");
}
if opcode.other_side_effects() {
return err!(inst, "Instruction with side effects must have an encoding");
}
Ok(())