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Reimplement simplify_cfg for SwitchInt

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First example of optimisation that applies to many more cases than originally.
This commit is contained in:
Simonas Kazlauskas 2017-02-02 08:41:01 +02:00
parent 92c56f607b
commit 64182a587c
1 changed files with 18 additions and 14 deletions
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32
src/librustc_mir/transform/simplify_branches.rs
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@ -30,26 +30,30 @@ impl<'l, 'tcx> MirPass<'tcx> for SimplifyBranches<'l> {
for block in mir.basic_blocks_mut() { for block in mir.basic_blocks_mut() {
let terminator = block.terminator_mut(); let terminator = block.terminator_mut();
terminator.kind = match terminator.kind { terminator.kind = match terminator.kind {
// TerminatorKind::If { ref targets, cond: Operand::Constant(Constant { TerminatorKind::SwitchInt { discr: Operand::Constant(Constant {
// literal: Literal::Value { literal: Literal::Value { ref value }, ..
// value: ConstVal::Bool(cond) }), ref values, ref targets, .. } => {
// }, .. if let Some(ref constint) = value.to_const_int() {
// }) } => { let (otherwise, targets) = targets.split_last().unwrap();
// if cond { let mut ret = TerminatorKind::Goto { target: *otherwise };
// TerminatorKind::Goto { target: targets.0 } for (v, t) in values.iter().zip(targets.iter()) {
// } else { if v == constint {
// TerminatorKind::Goto { target: targets.1 } ret = TerminatorKind::Goto { target: *t };
// } break;
// } }
}
ret
} else {
continue
}
},
TerminatorKind::Assert { target, cond: Operand::Constant(Constant { TerminatorKind::Assert { target, cond: Operand::Constant(Constant {
literal: Literal::Value { literal: Literal::Value {
value: ConstVal::Bool(cond) value: ConstVal::Bool(cond)
}, .. }, ..
}), expected, .. } if cond == expected => { }), expected, .. } if cond == expected => {
TerminatorKind::Goto { target: target } TerminatorKind::Goto { target: target }
} },
_ => continue _ => continue
}; };
} }