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Auto merge of #28428 - dotdash:same_adjust, r=nikomatsakis
Currently, we're generating adjustments, for example, to get from &[u8] to &[u8], which is unneeded and kicks us out of trans_into() into trans() which means an additional stack slot and copy in the unoptimized code.
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// Copyright 2015 The Rust Project Developers. See the COPYRIGHT | ||
// file at the top-level directory of this distribution and at | ||
// http://rust-lang.org/COPYRIGHT. | ||
// | ||
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
// option. This file may not be copied, modified, or distributed | ||
// except according to those terms. | ||
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// compile-flags: -C no-prepopulate-passes | ||
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// Hack to get the correct size for the length part in slices | ||
// CHECK: @helper([[USIZE:i[0-9]+]]) | ||
#[no_mangle] | ||
fn helper(_: usize) { | ||
} | ||
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// CHECK-LABEL: @no_op_slice_adjustment | ||
#[no_mangle] | ||
pub fn no_op_slice_adjustment(x: &[u8]) -> &[u8] { | ||
// We used to generate an extra alloca and memcpy for the block's trailing expression value, so | ||
// check that we copy directly to the return value slot | ||
// CHECK: [[SRC:%[0-9]+]] = bitcast { i8*, [[USIZE]] }* %x to | ||
// CHECK: [[DST:%[0-9]+]] = bitcast { i8*, [[USIZE]] }* %sret_slot to i8* | ||
// CHECK: call void @llvm.memcpy.{{.*}}(i8* [[DST]], i8* [[SRC]], | ||
{ x } | ||
} |