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trim get_structure and put_structure arities when last arg is an index ptr (#1536)

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This commit is contained in:
Mark Thom
2022-07-22 21:34:38 -06:00
parent ec9c763211
commit edea1273c8
2 changed files with 22 additions and 24 deletions
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23
src/codegen.rs
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@@ -263,6 +263,27 @@ impl DebrayAllocator {
} }
} }
// if the final argument of the structure is a Literal::Index,
// decrement the arity of the PutStructure instruction by 1.
fn trim_structure_by_last_arg(instr: &mut Instruction, last_arg: &Term) {
match instr {
Instruction::PutStructure(_, ref mut arity, _) |
Instruction::GetStructure(_, ref mut arity, _) => {
if let Term::Literal(_, Literal::CodeIndex(_)) = last_arg {
// it is acceptable if arity == 0 is the result of
// this decrement. call/N will have to read the index
// constant for '$call_inline' to succeed. to find it,
// it must know the heap location of the index.
// self.store must stop before reading the atom into a
// register.
*arity -= 1;
}
}
_ => {}
}
}
impl<'b> CodeGenerator<'b> { impl<'b> CodeGenerator<'b> {
pub(crate) fn new(atom_tbl: &'b mut AtomTable, settings: CodeGenSettings) -> Self { pub(crate) fn new(atom_tbl: &'b mut AtomTable, settings: CodeGenSettings) -> Self {
CodeGenerator { CodeGenerator {
@@ -375,7 +396,7 @@ impl<'b> CodeGenerator<'b> {
if let Some(instr) = target.last_mut() { if let Some(instr) = target.last_mut() {
if let Some(term) = terms.last() { if let Some(term) = terms.last() {
Target::trim_structure_by_last_arg(instr, term); trim_structure_by_last_arg(instr, term);
} }
} }

23
src/targets.rs
View File

@@ -36,8 +36,6 @@ pub(crate) trait CompilationTarget<'a> {
fn subterm_to_value(r: RegType) -> Instruction; fn subterm_to_value(r: RegType) -> Instruction;
fn clause_arg_to_instr(r: RegType) -> Instruction; fn clause_arg_to_instr(r: RegType) -> Instruction;
fn trim_structure_by_last_arg(instr: &mut Instruction, last_arg: &Term);
} }
impl<'a> CompilationTarget<'a> for FactInstruction { impl<'a> CompilationTarget<'a> for FactInstruction {
@@ -108,10 +106,6 @@ impl<'a> CompilationTarget<'a> for FactInstruction {
fn clause_arg_to_instr(val: RegType) -> Instruction { fn clause_arg_to_instr(val: RegType) -> Instruction {
Instruction::UnifyVariable(val) Instruction::UnifyVariable(val)
} }
fn trim_structure_by_last_arg(_instr: &mut Instruction, _last_arg: &Term) {
// a no-op for facts.
}
} }
impl<'a> CompilationTarget<'a> for QueryInstruction { impl<'a> CompilationTarget<'a> for QueryInstruction {
@@ -182,21 +176,4 @@ impl<'a> CompilationTarget<'a> for QueryInstruction {
fn clause_arg_to_instr(val: RegType) -> Instruction { fn clause_arg_to_instr(val: RegType) -> Instruction {
Instruction::SetValue(val) Instruction::SetValue(val)
} }
// if the final argument of the structure is a Literal::Index,
// decrement the arity of the PutStructure instruction by 1.
fn trim_structure_by_last_arg(instr: &mut Instruction, last_arg: &Term) {
if let Instruction::PutStructure(_, ref mut arity, _) = instr {
if let Term::Literal(_, Literal::CodeIndex(_)) = last_arg {
// it is acceptable if arity == 0 is the result of
// this decrement. call/N will have to read the index
// constant for '$call_inline' to succeed. to find it,
// it must know the heap location of the index.
// self.store must stop before reading the atom into a
// register.
*arity -= 1;
}
}
}
} }