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Auto merge of #29963 - dotdash:fat_copy, r=eddyb

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Since fat pointers do not qualify as structural types, they got copied
using load_ty and store_ty, which means that we load an FCA and use
extractvalue to get the components of the fat pointer. This breaks
certain optimizations in LLVM.

Found via apasel422/ref_count#13
This commit is contained in:
bors 2015-11-21 22:08:26 +00:00
commit eb19d024a9
2 changed files with 25 additions and 0 deletions
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3
src/librustc_trans/trans/base.rs
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@ -1223,6 +1223,9 @@ pub fn memcpy_ty<'blk, 'tcx>(bcx: Block<'blk, 'tcx>, dst: ValueRef, src: ValueRe
let llsz = llsize_of(ccx, llty); let llsz = llsize_of(ccx, llty);
let llalign = type_of::align_of(ccx, t); let llalign = type_of::align_of(ccx, t);
call_memcpy(bcx, dst, src, llsz, llalign as u32); call_memcpy(bcx, dst, src, llsz, llalign as u32);
} else if common::type_is_fat_ptr(bcx.tcx(), t) {
let (data, extra) = load_fat_ptr(bcx, src, t);
store_fat_ptr(bcx, data, extra, dst, t);
} else { } else {
store_ty(bcx, load_ty(bcx, src, t), dst, t); store_ty(bcx, load_ty(bcx, src, t), dst, t);
} }

22
src/test/codegen/fatptr.rs Normal file
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@ -0,0 +1,22 @@
// 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.
// compile-flags: -C no-prepopulate-passes
#![crate_type = "lib"]
pub trait T {}
// CHECK-LABEL: @copy_fat_ptr
#[no_mangle]
pub fn copy_fat_ptr(x: &T) {
// CHECK-NOT: extractvalue
let x2 = x;
}