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rust/src/test/mir-opt/simplify-locals-removes-unused-consts.rs

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Improve SimplifyLocals pass so it can remove unused consts The `ConstProp` can cause many locals to be initialized to a constant value and then never read from. `ConstProp` can also evaluate ZSTs into constant values. Previously, many of these would be removed by other parts of the MIR optimization pipeline. However, evaluating ZSTs (especially `()`) into constant values defeated those parts of the optimizer and so in a2e3ed5c054b544df6ceeb9e612d39af819f4aae, I added a hack to `ConstProp` that skips evaluating ZSTs to avoid that regression. This commit changes `SimplifyLocals` so that it doesn't consider writes of const values to a local to be a use of that local. In doing so, `SimplifyLocals` is able to remove otherwise unused locals left behind by other optimization passes (`ConstProp` in particular).
2019-10-17 05:46:51 -05:00
// compile-flags: -C overflow-checks=no
fn use_zst(_: ((), ())) { }
struct Temp {
x: u8
}
fn use_u8(_: u8) { }
fn main() {
let ((), ()) = ((), ());
use_zst(((), ()));
use_u8((Temp { x : 40 }).x + 2);
}
// END RUST SOURCE
// START rustc.main.SimplifyLocals.before.mir
// let mut _0: ();
// let mut _1: ((), ());
// let mut _2: ();
// let mut _3: ();
// let _4: ();
// let mut _5: ((), ());
// let mut _6: ();
// let mut _7: ();
// let _8: ();
// let mut _9: u8;
// let mut _10: u8;
// let mut _11: Temp;
// scope 1 {
// }
// bb0: {
// StorageLive(_1);
// StorageLive(_2);
Deduplicate and clean up pretty printing logic
2019-12-23 10:41:06 -06:00
// _2 = const ();
Improve SimplifyLocals pass so it can remove unused consts The `ConstProp` can cause many locals to be initialized to a constant value and then never read from. `ConstProp` can also evaluate ZSTs into constant values. Previously, many of these would be removed by other parts of the MIR optimization pipeline. However, evaluating ZSTs (especially `()`) into constant values defeated those parts of the optimizer and so in a2e3ed5c054b544df6ceeb9e612d39af819f4aae, I added a hack to `ConstProp` that skips evaluating ZSTs to avoid that regression. This commit changes `SimplifyLocals` so that it doesn't consider writes of const values to a local to be a use of that local. In doing so, `SimplifyLocals` is able to remove otherwise unused locals left behind by other optimization passes (`ConstProp` in particular).
2019-10-17 05:46:51 -05:00
// StorageLive(_3);
Deduplicate and clean up pretty printing logic
2019-12-23 10:41:06 -06:00
// _3 = const ();
// _1 = const ((), ());
Improve SimplifyLocals pass so it can remove unused consts The `ConstProp` can cause many locals to be initialized to a constant value and then never read from. `ConstProp` can also evaluate ZSTs into constant values. Previously, many of these would be removed by other parts of the MIR optimization pipeline. However, evaluating ZSTs (especially `()`) into constant values defeated those parts of the optimizer and so in a2e3ed5c054b544df6ceeb9e612d39af819f4aae, I added a hack to `ConstProp` that skips evaluating ZSTs to avoid that regression. This commit changes `SimplifyLocals` so that it doesn't consider writes of const values to a local to be a use of that local. In doing so, `SimplifyLocals` is able to remove otherwise unused locals left behind by other optimization passes (`ConstProp` in particular).
2019-10-17 05:46:51 -05:00
// StorageDead(_3);
// StorageDead(_2);
// StorageDead(_1);
// StorageLive(_4);
// StorageLive(_6);
Deduplicate and clean up pretty printing logic
2019-12-23 10:41:06 -06:00
// _6 = const ();
Improve SimplifyLocals pass so it can remove unused consts The `ConstProp` can cause many locals to be initialized to a constant value and then never read from. `ConstProp` can also evaluate ZSTs into constant values. Previously, many of these would be removed by other parts of the MIR optimization pipeline. However, evaluating ZSTs (especially `()`) into constant values defeated those parts of the optimizer and so in a2e3ed5c054b544df6ceeb9e612d39af819f4aae, I added a hack to `ConstProp` that skips evaluating ZSTs to avoid that regression. This commit changes `SimplifyLocals` so that it doesn't consider writes of const values to a local to be a use of that local. In doing so, `SimplifyLocals` is able to remove otherwise unused locals left behind by other optimization passes (`ConstProp` in particular).
2019-10-17 05:46:51 -05:00
// StorageLive(_7);
Deduplicate and clean up pretty printing logic
2019-12-23 10:41:06 -06:00
// _7 = const ();
Improve SimplifyLocals pass so it can remove unused consts The `ConstProp` can cause many locals to be initialized to a constant value and then never read from. `ConstProp` can also evaluate ZSTs into constant values. Previously, many of these would be removed by other parts of the MIR optimization pipeline. However, evaluating ZSTs (especially `()`) into constant values defeated those parts of the optimizer and so in a2e3ed5c054b544df6ceeb9e612d39af819f4aae, I added a hack to `ConstProp` that skips evaluating ZSTs to avoid that regression. This commit changes `SimplifyLocals` so that it doesn't consider writes of const values to a local to be a use of that local. In doing so, `SimplifyLocals` is able to remove otherwise unused locals left behind by other optimization passes (`ConstProp` in particular).
2019-10-17 05:46:51 -05:00
// StorageDead(_7);
// StorageDead(_6);
Deduplicate and clean up pretty printing logic
2019-12-23 10:41:06 -06:00
// _4 = const use_zst(const ((), ())) -> bb1;
Improve SimplifyLocals pass so it can remove unused consts The `ConstProp` can cause many locals to be initialized to a constant value and then never read from. `ConstProp` can also evaluate ZSTs into constant values. Previously, many of these would be removed by other parts of the MIR optimization pipeline. However, evaluating ZSTs (especially `()`) into constant values defeated those parts of the optimizer and so in a2e3ed5c054b544df6ceeb9e612d39af819f4aae, I added a hack to `ConstProp` that skips evaluating ZSTs to avoid that regression. This commit changes `SimplifyLocals` so that it doesn't consider writes of const values to a local to be a use of that local. In doing so, `SimplifyLocals` is able to remove otherwise unused locals left behind by other optimization passes (`ConstProp` in particular).
2019-10-17 05:46:51 -05:00
// }
// bb1: {
// StorageDead(_4);
// StorageLive(_8);
// StorageLive(_10);
// StorageLive(_11);
Deduplicate and clean up pretty printing logic
2019-12-23 10:41:06 -06:00
// _11 = const {0x28 : Temp};
Improve SimplifyLocals pass so it can remove unused consts The `ConstProp` can cause many locals to be initialized to a constant value and then never read from. `ConstProp` can also evaluate ZSTs into constant values. Previously, many of these would be removed by other parts of the MIR optimization pipeline. However, evaluating ZSTs (especially `()`) into constant values defeated those parts of the optimizer and so in a2e3ed5c054b544df6ceeb9e612d39af819f4aae, I added a hack to `ConstProp` that skips evaluating ZSTs to avoid that regression. This commit changes `SimplifyLocals` so that it doesn't consider writes of const values to a local to be a use of that local. In doing so, `SimplifyLocals` is able to remove otherwise unused locals left behind by other optimization passes (`ConstProp` in particular).
2019-10-17 05:46:51 -05:00
// _10 = const 40u8;
// StorageDead(_10);
// _8 = const use_u8(const 42u8) -> bb2;
// }
// bb2: {
// StorageDead(_11);
// StorageDead(_8);
// return;
// }
// END rustc.main.SimplifyLocals.before.mir
// START rustc.main.SimplifyLocals.after.mir
// let mut _0: ();
// let _1: ();
// let _2: ();
// scope 1 {
// }
// bb0: {
// StorageLive(_1);
Deduplicate and clean up pretty printing logic
2019-12-23 10:41:06 -06:00
// _1 = const use_zst(const ((), ())) -> bb1;
Improve SimplifyLocals pass so it can remove unused consts The `ConstProp` can cause many locals to be initialized to a constant value and then never read from. `ConstProp` can also evaluate ZSTs into constant values. Previously, many of these would be removed by other parts of the MIR optimization pipeline. However, evaluating ZSTs (especially `()`) into constant values defeated those parts of the optimizer and so in a2e3ed5c054b544df6ceeb9e612d39af819f4aae, I added a hack to `ConstProp` that skips evaluating ZSTs to avoid that regression. This commit changes `SimplifyLocals` so that it doesn't consider writes of const values to a local to be a use of that local. In doing so, `SimplifyLocals` is able to remove otherwise unused locals left behind by other optimization passes (`ConstProp` in particular).
2019-10-17 05:46:51 -05:00
// }
// bb1: {
// StorageDead(_1);
// StorageLive(_2);
// _2 = const use_u8(const 42u8) -> bb2;
// }
// bb2: {
// StorageDead(_2);
// return;
// }
// END rustc.main.SimplifyLocals.after.mir
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