ac24299636
The `mir!` macro has multiple parts:
- An optional return type annotation.
- A sequence of zero or more local declarations.
- A mandatory starting anonymous basic block, which is brace-delimited.
- A sequence of zero of more additional named basic blocks.
Some `mir!` invocations use braces with a "block" style, like so:
```
mir! {
let _unit: ();
{
let non_copy = S(42);
let ptr = std::ptr::addr_of_mut!(non_copy);
// Inside `callee`, the first argument and `*ptr` are basically
// aliasing places!
Call(_unit = callee(Move(*ptr), ptr), ReturnTo(after_call), UnwindContinue())
}
after_call = {
Return()
}
}
```
Some invocations use parens with a "block" style, like so:
```
mir!(
let x: [i32; 2];
let one: i32;
{
x = [42, 43];
one = 1;
x = [one, 2];
RET = Move(x);
Return()
}
)
```
And some invocations uses parens with a "tighter" style, like so:
```
mir!({
SetDiscriminant(*b, 0);
Return()
})
```
This last style is generally used for cases where just the mandatory
starting basic block is present. Its braces are placed next to the
parens.
This commit changes all `mir!` invocations to use braces with a "block"
style. Why?
- Consistency is good.
- The contents of the invocation is a block of code, so it's odd to use
parens. They are more normally used for function-like macros.
- Most importantly, the next commit will enable rustfmt for
`tests/mir-opt/`. rustfmt is more aggressive about formatting macros
that use parens than macros that use braces. Without this commit's
changes, rustfmt would break a couple of `mir!` macro invocations that
use braces within `tests/mir-opt` by inserting an extraneous comma.
E.g.:
```
mir!(type RET = (i32, bool);, { // extraneous comma after ';'
RET.0 = 1;
RET.1 = true;
Return()
})
```
Switching those `mir!` invocations to use braces avoids that problem,
resulting in this, which is nicer to read as well as being valid
syntax:
```
mir! {
type RET = (i32, bool);
{
RET.0 = 1;
RET.1 = true;
Return()
}
}
```
38 lines
1.1 KiB
Rust
38 lines
1.1 KiB
Rust
// skip-filecheck
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//@ test-mir-pass: CopyProp
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//
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// This attempts to mutate `a` via a pointer derived from `addr_of!(a)`. That is UB
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// according to Miri. However, the decision to make this UB - and to allow
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// rustc to rely on that fact for the purpose of optimizations - has not been
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// finalized.
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//
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// As such, we include this test to ensure that copy prop does not rely on that
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// fact. Specifically, if `addr_of!(a)` could not be used to modify a, it would
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// be correct for CopyProp to replace all occurrences of `a` with `c` - but that
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// would cause `f(true)` to output `false` instead of `true`.
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#![feature(custom_mir, core_intrinsics)]
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#![allow(unused_assignments)]
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extern crate core;
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use core::intrinsics::mir::*;
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#[custom_mir(dialect = "analysis", phase = "post-cleanup")]
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fn f(c: bool) -> bool {
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mir! {
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{
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let a = c;
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let p = core::ptr::addr_of!(a);
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let p2 = core::ptr::addr_of_mut!(*p);
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*p2 = false;
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RET = c;
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Return()
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}
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}
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}
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fn main() {
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assert_eq!(true, f(true));
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}
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// EMIT_MIR mutate_through_pointer.f.CopyProp.diff
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