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Add a MIR transform to remove fake reads

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As we are now creating borrows of places that may not be valid for
borrow checking matches, these have to be removed to avoid generating
broken code.
This commit is contained in:
Matthew Jasper 2018-09-23 10:43:14 +01:00
parent 1a6ed0271e
commit f71f733d48
4 changed files with 188 additions and 3 deletions
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122
src/test/mir-opt/remove_fake_borrows.rs Normal file
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// Test that the fake borrows for matches are removed after borrow checking.
// ignore-wasm32-bare
#![feature(nll)]
fn match_guard(x: Option<&&i32>) -> i32 {
match x {
Some(0) if true => 0,
_ => 1,
}
}
fn main() {
match_guard(None);
}
// END RUST SOURCE
// START rustc.match_guard.CleanFakeReadsAndBorrows.before.mir
// bb0: {
// FakeRead(ForMatchedPlace, _1);
// _2 = discriminant(_1);
// _3 = &shallow _1;
// _4 = &shallow ((_1 as Some).0: &'<empty> &'<empty> i32);
// _5 = &shallow (*((_1 as Some).0: &'<empty> &'<empty> i32));
// _6 = &shallow (*(*((_1 as Some).0: &'<empty> &'<empty> i32)));
// switchInt(move _2) -> [1isize: bb6, otherwise: bb4];
// }
// bb1: {
// _0 = const 0i32;
// goto -> bb9;
// }
// bb2: {
// _0 = const 1i32;
// goto -> bb9;
// }
// bb3: {
// FakeRead(ForMatchGuard, _3);
// FakeRead(ForMatchGuard, _4);
// FakeRead(ForMatchGuard, _5);
// FakeRead(ForMatchGuard, _6);
// goto -> bb7;
// }
// bb4: {
// FakeRead(ForMatchGuard, _3);
// FakeRead(ForMatchGuard, _4);
// FakeRead(ForMatchGuard, _5);
// FakeRead(ForMatchGuard, _6);
// goto -> bb2;
// }
// bb5: {
// unreachable;
// }
// bb6: {
// switchInt((*(*((_1 as Some).0: &'<empty> &'<empty> i32)))) -> [0i32: bb3, otherwise: bb4];
// }
// bb7: {
// goto -> bb1;
// }
// bb8: {
// goto -> bb4;
// }
// bb9: {
// return;
// }
// bb10: {
// resume;
// }
// END rustc.match_guard.CleanFakeReadsAndBorrows.before.mir
// START rustc.match_guard.CleanFakeReadsAndBorrows.after.mir
// bb0: {
// nop;
// _2 = discriminant(_1);
// nop;
// nop;
// nop;
// nop;
// switchInt(move _2) -> [1isize: bb6, otherwise: bb4];
// }
// bb1: {
// _0 = const 0i32;
// goto -> bb9;
// }
// bb2: {
// _0 = const 1i32;
// goto -> bb9;
// }
// bb3: {
// nop;
// nop;
// nop;
// nop;
// goto -> bb7;
// }
// bb4: {
// nop;
// nop;
// nop;
// nop;
// goto -> bb2;
// }
// bb5: {
// unreachable;
// }
// bb6: {
// switchInt((*(*((_1 as Some).0: &'<empty> &'<empty> i32)))) -> [0i32: bb3, otherwise: bb4];
// }
// bb7: {
// goto -> bb1;
// }
// bb8: {
// goto -> bb4;
// }
// bb9: {
// return;
// }
// bb10: {
// resume;
// }
// END rustc.match_guard.CleanFakeReadsAndBorrows.after.mir