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LLVM can usually optimize these away, but especially for things like transmutes of newtypes it's silly to generate the `alloc`+`store`+`load` at all when it's actually a nop at LLVM level.
59 lines
1.8 KiB
Rust
59 lines
1.8 KiB
Rust
// compile-flags: -O -C no-prepopulate-passes
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// min-llvm-version: 15.0 # this test assumes `ptr`s and thus no `pointercast`s
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#![crate_type = "lib"]
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// With opaque ptrs in LLVM, `transmute` can load/store any `alloca` as any type,
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// without needing to pointercast, and SRoA will turn that into a `bitcast`.
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// Thus memory-to-memory transmutes don't need to generate them ourselves.
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// However, `bitcast`s and `ptrtoint`s and `inttoptr`s are still worth doing when
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// that allows us to avoid the `alloca`s entirely; see `rvalue_creates_operand`.
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// CHECK-LABEL: define{{.*}}i32 @f32_to_bits(float noundef %x)
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// CHECK: %0 = bitcast float %x to i32
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// CHECK-NEXT: ret i32 %0
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#[no_mangle]
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pub fn f32_to_bits(x: f32) -> u32 {
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unsafe { std::mem::transmute(x) }
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}
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// CHECK-LABEL: define{{.*}}i8 @bool_to_byte(i1 noundef zeroext %b)
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// CHECK: %0 = zext i1 %b to i8
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// CHECK-NEXT: ret i8 %0
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#[no_mangle]
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pub fn bool_to_byte(b: bool) -> u8 {
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unsafe { std::mem::transmute(b) }
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}
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// CHECK-LABEL: define{{.*}}noundef zeroext i1 @byte_to_bool(i8 noundef %byte)
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// CHECK: %0 = trunc i8 %byte to i1
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// CHECK-NEXT: ret i1 %0
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#[no_mangle]
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pub unsafe fn byte_to_bool(byte: u8) -> bool {
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std::mem::transmute(byte)
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}
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// CHECK-LABEL: define{{.*}}ptr @ptr_to_ptr(ptr noundef %p)
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// CHECK: ret ptr %p
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#[no_mangle]
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pub fn ptr_to_ptr(p: *mut u16) -> *mut u8 {
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unsafe { std::mem::transmute(p) }
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}
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// CHECK: define{{.*}}[[USIZE:i[0-9]+]] @ptr_to_int(ptr noundef %p)
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// CHECK: %0 = ptrtoint ptr %p to [[USIZE]]
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// CHECK-NEXT: ret [[USIZE]] %0
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#[no_mangle]
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pub fn ptr_to_int(p: *mut u16) -> usize {
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unsafe { std::mem::transmute(p) }
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}
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// CHECK: define{{.*}}ptr @int_to_ptr([[USIZE]] noundef %i)
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// CHECK: %0 = inttoptr [[USIZE]] %i to ptr
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// CHECK-NEXT: ret ptr %0
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#[no_mangle]
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pub fn int_to_ptr(i: usize) -> *mut u16 {
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unsafe { std::mem::transmute(i) }
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}
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