Generate getelementptr instead of inttoptr for ptr::invalid

[joboet]

Currently, ptr::invalid generates an inttoptr, which means LLVM doesn't know that the pointer shouldn't have provenance. This PR changes the implementation so that a getelementptr relative to the null pointer is generated, which LLVM knows not to have provenance.

[rustbot]

r? @Mark-Simulacrum

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[scottmcm]

Oh, nice touch. Yeah, today this is inttoptr, so less of that sounds good to me.

EDIT: Doh, you had a better link in the OP 🤦

[scottmcm]

@bors r+

[bors]

📌 Commit 721f991 has been approved by scottmcm

It is now in the queue for this repository.

[joboet]

@bors r-
@rustbot ready

[Noratrieb]

@bors=scottmcm,Nilstrieb

[scottmcm]

@bors r=scottmcm,Nilstrieb

[bors]

📌 Commit bb399b1 has been approved by scottmcm,Nilstrieb

It is now in the queue for this repository.

[bors]

⌛ Testing commit b6d7805 with merge bd7aded...

[rust-log-analyzer]

The job test-various failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

test [mir-opt] tests/mir-opt/inline/polymorphic_recursion.rs ... ok

failures:

---- [mir-opt] tests/mir-opt/dataflow-const-prop/default_boxed_slice.rs stdout ----
14           scope 3 {
15               debug ptr => _3;
16           }
-           scope 4 (inlined Unique::<[bool; 0]>::dangling) {
-               let mut _5: std::ptr::NonNull<[bool; 0]>;
-               scope 5 (inlined NonNull::<[bool; 0]>::dangling) {
-                   scope 6 {
-                       let _6: *mut [bool; 0];
-                       scope 7 {
-                           debug ptr => _6;
-                           scope 12 (inlined NonNull::<[bool; 0]>::new_unchecked) {
-                               debug ptr => _6;
-                               let mut _8: bool;
-                               let _9: ();
-                               let mut _10: *mut ();
-                               let mut _11: *const [bool; 0];
-                               scope 13 {
-                           }
-                       }
-                       }
-                       scope 8 (inlined dangling_mut::<[bool; 0]>) {
-                           let mut _7: usize;
-                           scope 9 (inlined align_of::<[bool; 0]>) {
-                           }
-                           scope 10 (inlined without_provenance_mut::<[bool; 0]>) {
-                               debug addr => _7;
-                               scope 11 {
-                           }
-                       }
-                   }
-               }
-               }
-           }
47       }
48   
49       bb0: {

50           StorageLive(_1);
51           StorageLive(_2);
52           StorageLive(_3);
-           StorageLive(_9);
54           StorageLive(_4);
-           StorageLive(_5);
-           StorageLive(_6);
-           StorageLive(_7);
- -         _7 = AlignOf([bool; 0]);
- -         _6 = _7 as *mut [bool; 0] (Transmute);
- +         _7 = const 1_usize;
- +         _6 = const {0x1 as *mut [bool; 0]};
-           StorageDead(_7);
-           StorageLive(_10);
-           StorageLive(_11);
-           StorageLive(_8);
-           _8 = cfg!(debug_assertions);
-           switchInt(move _8) -> [0: bb3, otherwise: bb2];
+           _4 = Unique::<[bool; 0]>::dangling() -> [return: bb2, unwind unreachable];
69   
70       bb1: {

73       }
73       }
74   
75       bb2: {
- -         _10 = _6 as *mut () (PtrToPtr);
- -         _9 = NonNull::<T>::new_unchecked::precondition_check(move _10) -> [return: bb3, unwind unreachable];
- +         _10 = const {0x1 as *mut ()};
- +         _9 = NonNull::<T>::new_unchecked::precondition_check(const {0x1 as *mut ()}) -> [return: bb3, unwind unreachable];
-   
-       bb3: {
-           StorageDead(_8);
-           StorageDead(_8);
- -         _11 = _6 as *const [bool; 0] (PointerCoercion(MutToConstPointer));
- -         _5 = NonNull::<[bool; 0]> { pointer: _11 };
- +         _11 = const {0x1 as *const [bool; 0]};
- +         _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};
-           StorageDead(_11);
-           StorageDead(_10);
-           StorageDead(_6);
- -         _4 = Unique::<[bool; 0]> { pointer: move _5, _marker: const PhantomData::<[bool; 0]> };
- +         _4 = const Unique::<[bool; 0]> {{ pointer: NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }}, _marker: PhantomData::<[bool; 0]> }};
-           StorageDead(_5);
- -         _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize));
- +         _3 = const Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC0, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }};
+           _3 = move _4 as std::ptr::Unique<[bool]> (PointerCoercion(Unsize));
96           StorageDead(_4);
- -         _2 = Box::<[bool]>(_3, const std::alloc::Global);
- +         _2 = const Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC1, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global);
-           StorageDead(_9);
+           _2 = Box::<[bool]>(_3, const std::alloc::Global);
100           StorageDead(_3);
- -         _1 = A { foo: move _2 };
- +         _1 = const A {{ foo: Box::<[bool]>(Unique::<[bool]> {{ pointer: NonNull::<[bool]> {{ pointer: Indirect { alloc_id: ALLOC2, offset: Size(0 bytes) }: *const [bool] }}, _marker: PhantomData::<[bool]> }}, std::alloc::Global) }};
+           _1 = A { foo: move _2 };
103           StorageDead(_2);
104           _0 = const ();
105           drop(_1) -> [return: bb1, unwind unreachable];
106       }
- + }
- + 
- + 
- + ALLOC2 (size: 8, align: 4) {
- +     01 00 00 00 00 00 00 00                         │ ........
- + }
- + 
- + ALLOC1 (size: 8, align: 4) {
- +     01 00 00 00 00 00 00 00                         │ ........
- + }
- + 
- + ALLOC0 (size: 8, align: 4) {
- +     01 00 00 00 00 00 00 00                         │ ........
120   
121 

thread '[mir-opt] tests/mir-opt/dataflow-const-prop/default_boxed_slice.rs' panicked at src/tools/compiletest/src/runtest.rs:4141:21:
thread '[mir-opt] tests/mir-opt/dataflow-const-prop/default_boxed_slice.rs' panicked at src/tools/compiletest/src/runtest.rs:4141:21:
Actual MIR output differs from expected MIR output /checkout/tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-abort.diff


failures:
    [mir-opt] tests/mir-opt/dataflow-const-prop/default_boxed_slice.rs

[bors]

💔 Test failed - checks-actions

[scottmcm]

Looks like mir-opt tests need blessing?
@bors r-

[joboet]

As without_provenance is much more complicated now, it doesn't get inlined in as many places. Let's see what perf has to say about that...

@bors try @rust-timer queue

[bors]

⌛ Trying commit b6d7805 with merge f186eed...

[RalfJung]

As without_provenance is much more complicated now, it doesn't get inlined in as many places. Let's see what perf has to say about that...

Even with inline(always)?

EDIT: Ah, mir-opt tests. So it's about the MIR inliner, not the LLVM one.

[bors]

☀️ Try build successful - checks-actions
Build commit: f186eed (f186eedbfad18048274aca0c85fc40750cf0ba1b)

[rust-timer]

Finished benchmarking commit (f186eed): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: -S-waiting-on-perf +perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.6%	[0.2%, 1.2%]	21
Regressions ❌ (secondary)	1.1%	[0.2%, 1.9%]	5
Improvements ✅ (primary)	-0.9%	[-1.6%, -0.2%]	5
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.3%	[-1.6%, 1.2%]	26

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	3.0%	[0.9%, 6.6%]	5
Regressions ❌ (secondary)	5.2%	[5.1%, 5.4%]	2
Improvements ✅ (primary)	-6.1%	[-11.0%, -1.2%]	4
Improvements ✅ (secondary)	-2.8%	[-2.8%, -2.8%]	1
All ❌✅ (primary)	-1.1%	[-11.0%, 6.6%]	9

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.0%	[1.0%, 1.1%]	2
Regressions ❌ (secondary)	1.3%	[1.3%, 1.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.0%	[1.0%, 1.1%]	2

Binary size

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.7%	[0.0%, 1.7%]	82
Regressions ❌ (secondary)	2.4%	[0.1%, 14.7%]	19
Improvements ✅ (primary)	-0.9%	[-3.5%, -0.0%]	10
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.5%	[-3.5%, 1.7%]	92

Bootstrap: 653.837s -> 655.456s (0.25%)
Artifact size: 175.50 MiB -> 175.51 MiB (0.01%)

[scottmcm]

With #121282 looking like it might be able to land, maybe we won't end up needing this one after all?

[joboet]

With #121282 looking like it might be able to land, maybe we won't end up needing this one after all?

Definitely, and when looking at the compile-time regressions this causes, that's a good thing.