test.ll

; ModuleID = 'test.rc'
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

%struct.Foo = type { [10 x i64] }
%tydesc = type { i64, i64, void ({}*, i8*)*, void ({}*, i8*)*, void ({}*, i8*)*, void ({}*, i8*)*, i64, { i8*, i64 } }

@_rust_crate_map_toplevel = global { i32, i64, [2 x i64] } { i32 1, i64 ptrtoint ([1 x { i64, i64 }]* @_rust_mod_map to i64), [2 x i64] [i64 ptrtoint (i64* @_rust_crate_map_std_0.9-pre_6c65cf4b443341b1 to i64), i64 0] }
@_rust_crate_map_std_0.9-pre_6c65cf4b443341b1 = external global i64
@_rust_mod_map = internal global [1 x { i64, i64 }] zeroinitializer
@rust_abi_version = constant i64 1

; Function Attrs: noinline nounwind uwtable
define internal fastcc void @_ZN5test119hd4142abcf19795f7an4v0.0E(%struct.Foo* noalias nocapture sret) #0 {
"function top level":
  %1 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 0
  store i64 1, i64* %1, align 8
  %2 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 1
  store i64 2, i64* %2, align 8
  %3 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 2
  store i64 3, i64* %3, align 8
  %4 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 3
  store i64 4, i64* %4, align 8
  %5 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 4
  store i64 5, i64* %5, align 8
  %6 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 5
  store i64 6, i64* %6, align 8
  %7 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 6
  store i64 7, i64* %7, align 8
  %8 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 7
  store i64 8, i64* %8, align 8
  %9 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 8
  store i64 9, i64* %9, align 8
  %10 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 9
  store i64 0, i64* %10, align 8
  ret void
}

; Function Attrs: noinline nounwind uwtable
define internal fastcc void @_ZN5test219hd4142abcf19795f7aD4v0.0E(%struct.Foo* noalias nocapture sret) #0 {
"function top level":
  %f.sroa.0.0.idx = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 0
  store i64 1, i64* %f.sroa.0.0.idx, align 8
  %f.sroa.2.0.idx1 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 1
  store i64 2, i64* %f.sroa.2.0.idx1, align 8
  %f.sroa.3.0.idx2 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 2
  store i64 3, i64* %f.sroa.3.0.idx2, align 8
  %f.sroa.4.0.idx3 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 3
  store i64 2, i64* %f.sroa.4.0.idx3, align 8
  %f.sroa.6.0.idx4 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 4
  store i64 5, i64* %f.sroa.6.0.idx4, align 8
  %f.sroa.7.0.idx5 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 5
  store i64 6, i64* %f.sroa.7.0.idx5, align 8
  %f.sroa.8.0.idx6 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 6
  store i64 7, i64* %f.sroa.8.0.idx6, align 8
  %f.sroa.9.0.idx7 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 7
  store i64 8, i64* %f.sroa.9.0.idx7, align 8
  %f.sroa.10.0.idx8 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 8
  store i64 9, i64* %f.sroa.10.0.idx8, align 8
  %f.sroa.11.0.idx9 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 9
  store i64 0, i64* %f.sroa.11.0.idx9, align 8
  ret void
}

; Function Attrs: nounwind uwtable
define internal void @_ZN4main18hd7d397690bb6180a64v0.0E({ i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone) #1 {
"function top level":
  %_1 = alloca %struct.Foo, align 8
  %_2 = alloca %struct.Foo, align 8
  call fastcc void @_ZN5test119hd4142abcf19795f7an4v0.0E(%struct.Foo* sret %_1)
  call fastcc void @_ZN5test219hd4142abcf19795f7aD4v0.0E(%struct.Foo* sret %_2)
  ret void
}

define i64 @main(i64, i8**) {
top:
  %2 = tail call i64 @"_ZN8unstable4lang5start17hf72eb8b3c3a0a9aa11v0.9$x2dpreE"({ i64, %tydesc*, i8*, i8*, i8 }* null, i8* bitcast (void ({ i64, %tydesc*, i8*, i8*, i8 }*)* @_ZN4main18hd7d397690bb6180a64v0.0E to i8*), i64 %0, i8** %1)
  ret i64 %2
}

declare i64 @"_ZN8unstable4lang5start17hf72eb8b3c3a0a9aa11v0.9$x2dpreE"({ i64, %tydesc*, i8*, i8*, i8 }*, i8*, i64, i8**)

attributes #0 = { noinline nounwind uwtable }
attributes #1 = { nounwind uwtable }

test.rs

struct Foo {
    v: [int,..10]
}

#[inline(never)]
fn test1() -> Foo {
    Foo {
        v: [1,2,3,4,5,6,7,8,9,0]
    }
}

#[inline(never)]
fn test2() -> Foo {
    let mut f = Foo {
        v: [1,2,3,4,5,6,7,8,9,0]
    };

    f.v[3] = 2;

    f
}

fn main() {
    let _1 = test1();
    let _2 = test2();
}

test2.ll

define void @_ZN5test218h3b288a3d1579e11aD4v0.0E(%struct.Foo* noalias nocapture sret, { i64, %tydesc*, i8*, i8*, i8 }* nocapture readnone, i64) #0 {
"function top level":
  %g.sroa.0.sroa.0.0.idx = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 0
  store i64 %2, i64* %g.sroa.0.sroa.0.0.idx, align 8
  %g.sroa.0.sroa.2.0.idx25 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 1
  store i64 2, i64* %g.sroa.0.sroa.2.0.idx25, align 8
  %g.sroa.0.sroa.3.0.idx26 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 2
  store i64 3, i64* %g.sroa.0.sroa.3.0.idx26, align 8
  %g.sroa.2.0.idx7 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 3
  store i64 %2, i64* %g.sroa.2.0.idx7, align 8
  %g.sroa.3.sroa.0.0.idx = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 4
  store i64 5, i64* %g.sroa.3.sroa.0.0.idx, align 8
  %g.sroa.3.sroa.2.0.idx20 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 5
  store i64 6, i64* %g.sroa.3.sroa.2.0.idx20, align 8
  %g.sroa.3.sroa.3.0.idx21 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 6
  store i64 7, i64* %g.sroa.3.sroa.3.0.idx21, align 8
  %g.sroa.3.sroa.4.0.idx22 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 7
  store i64 8, i64* %g.sroa.3.sroa.4.0.idx22, align 8
  %g.sroa.3.sroa.5.0.idx23 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 8
  store i64 9, i64* %g.sroa.3.sroa.5.0.idx23, align 8
  %g.sroa.3.sroa.6.0.idx24 = getelementptr inbounds %struct.Foo* %0, i64 0, i32 0, i64 9
  store i64 0, i64* %g.sroa.3.sroa.6.0.idx24, align 8
  ret void
}

test2.rs

#[inline(never)]
fn test2(n:uint) -> Foo {
    let f = Foo {
        v: [n as int ,2,3,4,5,6,7,8,9,0]
    };

    let mut g = f;

    g.v[3] = f.v[0];

    return g;
}