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Add a codegen test for manually swapping a small `Copy` type 

To confirm we're not just helping `mem::swap`
This commit is contained in:
Scott McMurray 2023-05-26 01:23:55 -07:00
parent 9eee230cd0
commit cce0b52e7b
1 changed files with 20 additions and 0 deletions
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20
tests/codegen/swap-small-types.rs
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@ -8,10 +8,30 @@ use std::mem::swap;
type RGB48 = [u16; 3];
// CHECK-LABEL: @swap_rgb48_manually(
#[no_mangle]
pub fn swap_rgb48_manually(x: &mut RGB48, y: &mut RGB48) {
// CHECK-NOT: alloca
// CHECK: %temp = alloca [3 x i16]
// CHECK-NOT: alloca
// CHECK-NOT: call void @llvm.memcpy
// CHECK: call void @llvm.memcpy.{{.+}}({{.+}} %temp, {{.+}} %x, {{.+}} 6, {{.+}})
// CHECK: call void @llvm.memcpy.{{.+}}({{.+}} %x, {{.+}} %y, {{.+}} 6, {{.+}})
// CHECK: call void @llvm.memcpy.{{.+}}({{.+}} %y, {{.+}} %temp, {{.+}} 6, {{.+}})
// CHECK-NOT: call void @llvm.memcpy
let temp = *x;
*x = *y;
*y = temp;
}
// CHECK-LABEL: @swap_rgb48
#[no_mangle]
pub fn swap_rgb48(x: &mut RGB48, y: &mut RGB48) {
// FIXME MIR inlining messes up LLVM optimizations.
// If these checks start failing, please update this test.
// CHECK: alloca [3 x i16]
// CHECK: call void @llvm.memcpy
// WOULD-CHECK-NOT: alloca
// WOULD-CHECK: load i48
// WOULD-CHECK: store i48