Embedded Swift compiler emits explicit loop instead of memmove()

[michael-jan]

Description

When compiling in Full Swift mode, UnsafeMutablePointer’s update(from:count:) emits a call to memmove(). But in Embedded mode, a less performant explicit loop is emitted.

Reproduction

func f(dst: UnsafeMutablePointer<Int>, src: UnsafePointer<Int>) {
    dst.update(from: src, count: 123)
}

Godbolt: https://godbolt.org/z/s71Mxfoz5

Expected behavior

A call to memmove() is emitted.

Environment

Swift Development Snapshot 2024-08-03

Additional information

No response

[tbkka]

CC: @eeckstein