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Auto merge of #73453 - erikdesjardins:tuplayout, r=eddyb
Ignore ZST offsets when deciding whether to use Scalar/ScalarPair layout This is important because Scalar/ScalarPair layout previously would not be used if any ZST had nonzero offset. For example, before this change, only `((), u128)` would be laid out like `u128`, not `(u128, ())`. Fixes #63244
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,36 @@ | ||
| // ignore-emscripten | ||
| // compile-flags: -C no-prepopulate-passes | ||
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| // Test that tuples get optimized layout, in particular with a ZST in the last field (#63244) | ||
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| #![crate_type="lib"] | ||
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| type ScalarZstLast = (u128, ()); | ||
| // CHECK: define i128 @test_ScalarZstLast(i128 %_1) | ||
| #[no_mangle] | ||
| pub fn test_ScalarZstLast(_: ScalarZstLast) -> ScalarZstLast { loop {} } | ||
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| type ScalarZstFirst = ((), u128); | ||
| // CHECK: define i128 @test_ScalarZstFirst(i128 %_1) | ||
| #[no_mangle] | ||
| pub fn test_ScalarZstFirst(_: ScalarZstFirst) -> ScalarZstFirst { loop {} } | ||
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| type ScalarPairZstLast = (u8, u128, ()); | ||
| // CHECK: define { i128, i8 } @test_ScalarPairZstLast(i128 %_1.0, i8 %_1.1) | ||
| #[no_mangle] | ||
| pub fn test_ScalarPairZstLast(_: ScalarPairZstLast) -> ScalarPairZstLast { loop {} } | ||
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| type ScalarPairZstFirst = ((), u8, u128); | ||
| // CHECK: define { i8, i128 } @test_ScalarPairZstFirst(i8 %_1.0, i128 %_1.1) | ||
| #[no_mangle] | ||
| pub fn test_ScalarPairZstFirst(_: ScalarPairZstFirst) -> ScalarPairZstFirst { loop {} } | ||
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| type ScalarPairLotsOfZsts = ((), u8, (), u128, ()); | ||
| // CHECK: define { i128, i8 } @test_ScalarPairLotsOfZsts(i128 %_1.0, i8 %_1.1) | ||
| #[no_mangle] | ||
| pub fn test_ScalarPairLotsOfZsts(_: ScalarPairLotsOfZsts) -> ScalarPairLotsOfZsts { loop {} } | ||
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| type ScalarPairLottaNesting = (((), ((), u8, (), u128, ())), ()); | ||
| // CHECK: define { i128, i8 } @test_ScalarPairLottaNesting(i128 %_1.0, i8 %_1.1) | ||
| #[no_mangle] | ||
| pub fn test_ScalarPairLottaNesting(_: ScalarPairLottaNesting) -> ScalarPairLottaNesting { loop {} } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,43 @@ | ||
| // compile-flags: -C no-prepopulate-passes | ||
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| #![crate_type = "lib"] | ||
| #![feature(repr_simd)] | ||
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| // Hack to get the correct size for the length part in slices | ||
| // CHECK: @helper([[USIZE:i[0-9]+]] %_1) | ||
| #[no_mangle] | ||
| pub fn helper(_: usize) { | ||
| } | ||
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| // Check that we correctly generate a GEP for a ZST that is not included in Scalar layout | ||
| // CHECK-LABEL: @scalar_layout | ||
| #[no_mangle] | ||
| pub fn scalar_layout(s: &(u64, ())) { | ||
| // CHECK: [[X0:%[0-9]+]] = bitcast i64* %s to i8* | ||
| // CHECK-NEXT: [[X1:%[0-9]+]] = getelementptr i8, i8* [[X0]], [[USIZE]] 8 | ||
| let x = &s.1; | ||
| &x; // keep variable in an alloca | ||
| } | ||
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| // Check that we correctly generate a GEP for a ZST that is not included in ScalarPair layout | ||
| // CHECK-LABEL: @scalarpair_layout | ||
| #[no_mangle] | ||
| pub fn scalarpair_layout(s: &(u64, u32, ())) { | ||
| // CHECK: [[X0:%[0-9]+]] = bitcast { i64, i32 }* %s to i8* | ||
| // CHECK-NEXT: [[X1:%[0-9]+]] = getelementptr i8, i8* [[X0]], [[USIZE]] 12 | ||
| let x = &s.2; | ||
| &x; // keep variable in an alloca | ||
| } | ||
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| #[repr(simd)] | ||
| pub struct U64x4(u64, u64, u64, u64); | ||
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| // Check that we correctly generate a GEP for a ZST that is not included in Vector layout | ||
| // CHECK-LABEL: @vector_layout | ||
| #[no_mangle] | ||
| pub fn vector_layout(s: &(U64x4, ())) { | ||
| // CHECK: [[X0:%[0-9]+]] = bitcast <4 x i64>* %s to i8* | ||
| // CHECK-NEXT: [[X1:%[0-9]+]] = getelementptr i8, i8* [[X0]], [[USIZE]] 32 | ||
| let x = &s.1; | ||
| &x; // keep variable in an alloca | ||
| } |
26 changes: 26 additions & 0 deletions
26
src/test/ui/dynamically-sized-types/dst-tuple-no-reorder.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,26 @@ | ||
| // run-pass | ||
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| #![feature(unsized_tuple_coercion)] | ||
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| // Ensure that unsizable fields that might be accessed don't get reordered | ||
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| fn nonzero_size() { | ||
| let sized: (u8, [u32; 2]) = (123, [456, 789]); | ||
| let unsize: &(u8, [u32]) = &sized; | ||
| assert_eq!(unsize.0, 123); | ||
| assert_eq!(unsize.1.len(), 2); | ||
| assert_eq!(unsize.1[0], 456); | ||
| assert_eq!(unsize.1[1], 789); | ||
| } | ||
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| fn zst() { | ||
| let sized: (u8, [u32; 0]) = (123, []); | ||
| let unsize: &(u8, [u32]) = &sized; | ||
| assert_eq!(unsize.0, 123); | ||
| assert_eq!(unsize.1.len(), 0); | ||
| } | ||
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| pub fn main() { | ||
| nonzero_size(); | ||
| zst(); | ||
| } |
22 changes: 22 additions & 0 deletions
22
src/test/ui/dynamically-sized-types/dst-tuple-zst-offsets.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,22 @@ | ||
| // run-pass | ||
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| #![feature(unsized_tuple_coercion)] | ||
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| // Check that we do not change the offsets of ZST fields when unsizing | ||
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| fn scalar_layout() { | ||
| let sized: &(u8, [(); 13]) = &(123, [(); 13]); | ||
| let unsize: &(u8, [()]) = sized; | ||
| assert_eq!(sized.1.as_ptr(), unsize.1.as_ptr()); | ||
| } | ||
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| fn scalarpair_layout() { | ||
| let sized: &(u8, u16, [(); 13]) = &(123, 456, [(); 13]); | ||
| let unsize: &(u8, u16, [()]) = sized; | ||
| assert_eq!(sized.2.as_ptr(), unsize.2.as_ptr()); | ||
| } | ||
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| pub fn main() { | ||
| scalar_layout(); | ||
| scalarpair_layout(); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,27 @@ | ||
| // compile-flags: -Z mir-opt-level=2 | ||
| // build-pass | ||
| #![crate_type="lib"] | ||
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| // This used to ICE: const-prop did not account for field reordering of scalar pairs, | ||
| // and would generate a tuple like `(0x1337, VariantBar): (FooEnum, isize)`, | ||
| // causing assertion failures in codegen when trying to read 0x1337 at the wrong type. | ||
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| pub enum FooEnum { | ||
| VariantBar, | ||
| VariantBaz, | ||
| VariantBuz, | ||
| } | ||
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| pub fn wrong_index() -> isize { | ||
| let (_, b) = id((FooEnum::VariantBar, 0x1337)); | ||
| b | ||
| } | ||
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| pub fn wrong_index_two() -> isize { | ||
| let (_, (_, b)) = id(((), (FooEnum::VariantBar, 0x1338))); | ||
| b | ||
| } | ||
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| fn id<T>(x: T) -> T { | ||
| x | ||
| } |