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8dcc676c92
We already did `Transmute`-then-`PtrToPtr`; this adds the nearly-identical `PtrToPtr`-then-`Transmute`.
It also adds `transmute(Foo(x))` → `transmute(x)`, when `Foo` is a single-field transparent type. That's useful for things like `NonNull { pointer: p }.as_ptr()`.
Found these as I was looking at MCP807-related changes.
65 lines
2.2 KiB
Rust
65 lines
2.2 KiB
Rust
//@ test-mir-pass: InstSimplify-after-simplifycfg
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//@ compile-flags: -C panic=abort
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#![crate_type = "lib"]
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#![feature(core_intrinsics)]
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#![feature(custom_mir)]
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use std::intrinsics::mir::*;
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use std::mem::{ManuallyDrop, MaybeUninit, transmute};
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// EMIT_MIR combine_transmutes.identity_transmutes.InstSimplify-after-simplifycfg.diff
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pub unsafe fn identity_transmutes() {
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// CHECK-LABEL: fn identity_transmutes(
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// CHECK-NOT: as i32 (Transmute);
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// CHECK-NOT: as Vec<i32> (Transmute);
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// These are nops and should be removed
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let _a = transmute::<i32, i32>(1);
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let _a = transmute::<Vec<i32>, Vec<i32>>(Vec::new());
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}
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#[custom_mir(dialect = "runtime", phase = "initial")]
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// EMIT_MIR combine_transmutes.integer_transmutes.InstSimplify-after-simplifycfg.diff
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pub unsafe fn integer_transmutes() {
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// CHECK-LABEL: fn integer_transmutes(
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// CHECK-NOT: _i32 as u32 (Transmute);
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// CHECK: _i32 as u32 (IntToInt);
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// CHECK: _i32 as i64 (Transmute);
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// CHECK-NOT: _u64 as i64 (Transmute);
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// CHECK: _u64 as i64 (IntToInt);
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// CHECK: _u64 as u32 (Transmute);
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// CHECK-NOT: _isize as usize (Transmute);
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// CHECK: _isize as usize (IntToInt);
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mir! {
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{
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let A = CastTransmute::<i32, u32>(1); // Can be a cast
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let B = CastTransmute::<i32, i64>(1); // UB
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let C = CastTransmute::<u64, i64>(1); // Can be a cast
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let D = CastTransmute::<u64, u32>(1); // UB
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let E = CastTransmute::<isize, usize>(1); // Can be a cast
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Return()
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}
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}
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}
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// EMIT_MIR combine_transmutes.keep_transparent_transmute.InstSimplify-after-simplifycfg.diff
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pub unsafe fn keep_transparent_transmute() {
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// CHECK-LABEL: fn keep_transparent_transmute(
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// CHECK-NOT: .{{[0-9]+}}: i16
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// CHECK: as i16 (Transmute);
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// CHECK-NOT: .{{[0-9]+}}: i16
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// CHECK: as i16 (Transmute);
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// CHECK-NOT: .{{[0-9]+}}: i16
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// Transmutes should not be converted to field accesses, because MCP#807
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// bans projections into `[rustc_layout_scalar_valid_range_*]` types.
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let _a: i16 = transmute(const { std::num::NonZero::new(12345_i16).unwrap() });
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let _a: i16 = transmute(std::num::Wrapping(0_i16));
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}
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pub union Union32 {
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u32: u32,
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i32: i32,
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}
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