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[const-prop] Handle MIR Rvalue::Discriminant

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This commit is contained in:
Wesley Wiser 2019-09-15 00:05:19 -04:00
parent a2e3ed5c05
commit 4d89031e80
2 changed files with 55 additions and 2 deletions
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4
src/librustc_mir/transform/const_prop.rs
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@ -436,13 +436,13 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
// if this isn't a supported operation, then return None
match rvalue {
Rvalue::NullaryOp(NullOp::Box, _) |
Rvalue::Discriminant(..) => return None,
Rvalue::NullaryOp(NullOp::Box, _) => return None,
Rvalue::Use(_) |
Rvalue::Len(_) |
Rvalue::Repeat(..) |
Rvalue::Aggregate(..) |
Rvalue::Discriminant(..) |
Rvalue::Cast(..) |
Rvalue::NullaryOp(..) |
Rvalue::CheckedBinaryOp(..) |

53
src/test/mir-opt/const_prop/discriminant.rs Normal file
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@ -0,0 +1,53 @@
// compile-flags: -O
fn main() {
let x = (if let Some(true) = Some(true) { 42 } else { 10 }) + 0;
}
// END RUST SOURCE
// START rustc.main.ConstProp.before.mir
// bb0: {
// ...
// _3 = std::option::Option::<bool>::Some(const true,);
// _4 = discriminant(_3);
// switchInt(move _4) -> [1isize: bb3, otherwise: bb2];
// }
// bb1: {
// _2 = const 42i32;
// goto -> bb4;
// }
// bb2: {
// _2 = const 10i32;
// goto -> bb4;
// }
// bb3: {
// switchInt(((_3 as Some).0: bool)) -> [false: bb2, otherwise: bb1];
// }
// bb4: {
// _1 = Add(move _2, const 0i32);
// ...
// }
// END rustc.main.ConstProp.before.mir
// START rustc.main.ConstProp.after.mir
// bb0: {
// ...
// _3 = const Scalar(0x01) : std::option::Option<bool>;
// _4 = const 1isize;
// switchInt(const 1isize) -> [1isize: bb3, otherwise: bb2];
// }
// bb1: {
// _2 = const 42i32;
// goto -> bb4;
// }
// bb2: {
// _2 = const 10i32;
// goto -> bb4;
// }
// bb3: {
// switchInt(const true) -> [false: bb2, otherwise: bb1];
// }
// bb4: {
// _1 = Add(move _2, const 0i32);
// ...
// }
// END rustc.main.ConstProp.after.mir