Commit 56a352f

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Auto merge of #145411 - the8472:cows-have-no-branches, r=Mark-Simulacrum

regression test for Cow<[u8]> layout requested by ralf in #117763 (comment)

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	`1`	`+//@ compile-flags: -Copt-level=3`
	`2`	`+//@ needs-deterministic-layouts`
	`3`	`+`
	`4`	`+// Currently Vec<T> and &[T] have layouts that start with (pointer, len)`
	`5`	`+// which makes the conversion branchless.`
	`6`	`+// A nice-to-have property, not guaranteed.`
	`7`	`+#![crate_type = "cdylib"]`
	`8`	`+`
	`9`	`+// CHECK-LABEL: @branchless_cow_slices`
	`10`	`+#[no_mangle]`
	`11`	`+pub fn branchless_cow_slices<'a>(cow: &'a std::borrow::Cow<'a, [u8]>) -> &'a [u8] {`
	`12`	`+ // CHECK-NOT: br`
	`13`	`+ // CHECK-NOT: select`
	`14`	`+ // CHECK-NOT: icmp`
	`15`	`+ // CHECK: ret { ptr, {{i32\|i64}} }`
	`16`	`+ &*cow`
	`17`	`+}`

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