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Add a Place::is_indirect method to determine whether a Place contains a Deref projection #64005

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merged 2 commits into from
Sep 5, 2019

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@ecstatic-morse ecstatic-morse commented Aug 29, 2019

Working on #63860 requires tracking some property about each local. This requires differentiating Places like x and x.field[index] from ones like *x and *x.field, since the first two will always access the same region of memory as x while the latter two may access any region of memory. This functionality is duplicated in various places across the compiler. This PR adds a helper method to Place which determines whether that Place has a Deref projection at any point and changes some existing code to use the new method.

I've not converted qualify_consts.rs to use the new method, since it's not a trivial conversion and it will get replaced anyway by #63860. There may be other potential uses besides the two I change in this PR.

r? @oli-obk

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 29, 2019
This returns whether a `Place` references the same region of memory
as its base, or equivalently whether it contains a `Deref` projection.

This is helpful for analyses that must track state for locals, since an
assignment to `x` or `x.field` is fundamentally different than one to
`*x`, which may mutate any memory region.
@ecstatic-morse ecstatic-morse force-pushed the is-indirect branch 2 times, most recently from bd8c5d1 to e9e075f Compare August 29, 2019 20:56
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From the changes in this PR it looks to me like all use cases could use the find_local function instead?


true
})
PlaceBase::Local(_) => true,
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What do you think about changing the true to !place.is_indirect()?

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That works better.

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oli-obk commented Aug 29, 2019

r? @spastorino this looks like something right up your alley

@rust-highfive rust-highfive assigned spastorino and unassigned oli-obk Aug 29, 2019
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Nice work and looks good to me. I'm not sure I like the name of the function but can't think of a better one right now. Any other ideas?, @oli-obk do you consider the fn name good enough? any better ideas?.

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oli-obk commented Sep 4, 2019

@bors r+

Nope, no better ideas here

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bors commented Sep 4, 2019

📌 Commit 96ac02b has been approved by oli-obk

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 4, 2019
Centril added a commit to Centril/rust that referenced this pull request Sep 5, 2019
Add a `Place::is_indirect` method to determine whether a `Place` contains a `Deref` projection

Working on rust-lang#63860 requires tracking some property about each local. This requires differentiating `Place`s like `x` and `x.field[index]` from ones like `*x` and `*x.field`, since the first two will always access the same region of memory as `x` while the latter two may access any region of memory. This functionality is duplicated in various places across the compiler. This PR adds a helper method to `Place` which determines whether that `Place` has a `Deref` projection at any point and changes some existing code to use the new method.

I've not converted `qualify_consts.rs` to use the new method, since it's not a trivial conversion and it will get replaced anyway by rust-lang#63860. There may be other potential uses besides the two I change in this PR.

r? @oli-obk
Centril added a commit to Centril/rust that referenced this pull request Sep 5, 2019
Add a `Place::is_indirect` method to determine whether a `Place` contains a `Deref` projection

Working on rust-lang#63860 requires tracking some property about each local. This requires differentiating `Place`s like `x` and `x.field[index]` from ones like `*x` and `*x.field`, since the first two will always access the same region of memory as `x` while the latter two may access any region of memory. This functionality is duplicated in various places across the compiler. This PR adds a helper method to `Place` which determines whether that `Place` has a `Deref` projection at any point and changes some existing code to use the new method.

I've not converted `qualify_consts.rs` to use the new method, since it's not a trivial conversion and it will get replaced anyway by rust-lang#63860. There may be other potential uses besides the two I change in this PR.

r? @oli-obk
bors added a commit that referenced this pull request Sep 5, 2019
Rollup of 15 pull requests

Successful merges:

 - #62860 (Stabilize checked_duration_since for 1.38.0)
 - #63549 (Rev::rposition counts from the wrong end)
 - #63985 (Stabilize pin_into_inner in 1.39.0)
 - #64005 (Add a `Place::is_indirect` method to determine whether a `Place` contains a `Deref` projection)
 - #64031 (Harden `param_attrs` test wrt. usage of a proc macro `#[attr]`)
 - #64038 (Check impl trait substs when checking for recursive types)
 - #64043 (Add some more tests for underscore imports)
 - #64092 (Update xLTO compatibility table in rustc book.)
 - #64110 (Refer to "`self` type" instead of "receiver type")
 - #64120 (Move path parsing earlier)
 - #64123 (Added warning around code with reference to uninit bytes)
 - #64128 (unused_parens: account for or-patterns and `&(mut x)`)
 - #64141 (Minimize uses of `LocalInternedString`)
 - #64142 (Fix doc links in `std::cmp` module)
 - #64148 (fix a few typos in comments)

Failed merges:

r? @ghost
@bors bors merged commit 96ac02b into rust-lang:master Sep 5, 2019
@ecstatic-morse ecstatic-morse deleted the is-indirect branch October 6, 2020 01:42
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5 participants