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//! Peephole optimizations that can be performed while creating clif ir.
use cranelift_codegen::ir::{condcodes::IntCC, InstructionData, Opcode, Value, ValueDef};
use cranelift_frontend::FunctionBuilder;
/// If the given value was produced by the lowering of `Rvalue::Not` return the input and true,
/// otherwise return the given value and false.
pub(crate) fn maybe_unwrap_bool_not(bcx: &mut FunctionBuilder<'_>, arg: Value) -> (Value, bool) {
if let ValueDef::Result(arg_inst, 0) = bcx.func.dfg.value_def(arg) {
match bcx.func.dfg[arg_inst] {
// This is the lowering of `Rvalue::Not`
InstructionData::IntCompareImm {
opcode: Opcode::IcmpImm,
cond: IntCC::Equal,
arg,
imm,
} if imm.bits() == 0 => (arg, true),
_ => (arg, false),
}
} else {
(arg, false)
}
}
/// Returns whether the branch is statically known to be taken or `None` if it isn't statically known.
pub(crate) fn maybe_known_branch_taken(
bcx: &FunctionBuilder<'_>,
arg: Value,
test_zero: bool,
) -> Option<bool> {
let arg_inst = if let ValueDef::Result(arg_inst, 0) = bcx.func.dfg.value_def(arg) {
arg_inst
} else {
return None;
};
match bcx.func.dfg[arg_inst] {
InstructionData::UnaryImm { opcode: Opcode::Iconst, imm } => {
if test_zero {
Some(imm.bits() == 0)
} else {
Some(imm.bits() != 0)
}
}
_ => None,
}
}
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