Repository: rust
Issue: right shift of i128i by zero fails on s390x (SystemZ)
Labels: O-SPARC,C-bug,O-SystemZ

I've set up a repository that reproduces this issue on travis (using qemu): https://github.com/gnzlbg/repro_s390x 

The following code right shifts a `<1 x i128>` containing `1` by `0`. The result of the shift should be `1`, but on debug builds it is `0`, causing the following code to panic (on release the code does not panic):

```rust
#![feature(repr_simd, platform_intrinsics)]
#![allow(non_camel_case_types)]

#[derive(Copy,Clone)]
#[repr(simd)]
pub struct i128x1(i128);

extern "platform-intrinsic" {
    pub fn simd_shr<T>(x: T, y: T) -> T;
}

#[test]
pub fn test() {
    unsafe {
        let z = i128x1(0 as i128);
        let o = i128x1(1 as i128);

        if simd_shr(o, z).0 !=  o.0 {
            panic!();
        }
    }
}
```

The `test` function generates the following LLVM-IR

```llvm
define void @repro_s390x::test() unnamed_addr #0 {
start:
%tmp_ret = alloca <1 x i128>, align 16
%o = alloca <1 x i128>, align 16
%z = alloca <1 x i128>, align 16
%0 = bitcast <1 x i128>* %z to i128*
store i128 0, i128* %0, align 8
%1 = bitcast <1 x i128>* %o to i128*
store i128 1, i128* %1, align 8
%2 = load <1 x i128>, <1 x i128>* %o, align 16
%3 = load <1 x i128>, <1 x i128>* %z, align 16
%4 = ashr <1 x i128> %2, %3
store <1 x i128> %4, <1 x i128>* %tmp_ret, align 16
%5 = load <1 x i128>, <1 x i128>* %tmp_ret, align 16
br label %bb1

bb1:                                              ; preds = %start
%6 = bitcast <1 x i128> %5 to i128
%7 = bitcast <1 x i128>* %o to i128*
%8 = load i128, i128* %7, align 8
%9 = icmp ne i128 %6, %8
br i1 %9, label %bb2, label %bb3

bb2:                                              ; preds = %bb1
; call std::panicking::begin_panic
call void @_ZN3std9panicking11begin_panic17h3f2f8b63a0f87b42E([0 x i8]* noalias nonnull readonly bitcast (<{ [14 x i8] }>* @byte_str.2 to [0 x i8]*), i64 14, { [0 x i64], { [0 x i8]*, i64 }, [0 x i32], i32, [0 x i32], i32, [0 x i32] }* noalias readonly dereferenceable(24) bitcast (<{ i8*, [16 x i8] }>* @byte_str.1 to { [0 x i64], { [0 x i8]*, i64 }, [0 x i32], i32, [0 x i32], i32, [0 x i32] }*))
unreachable

bb3:                                              ; preds = %bb1
ret void
}
```

which is lowered to

```asm
repro_s390x::test (src/lib.rs:12):
 stmg    %r11, %r15, 88(%r15)
 aghi    %r15, -240
 lgr     %r11, %r15
 lgr     %r0, %r15
 lgr     %r1, %r0
 aghi    %r1, -24
 la      %r0, 168(%r1)
 lgr     %r2, %r0
 nill    %r2, 65520
 lgr     %r15, %r1
 lgr     %r0, %r15
 lgr     %r1, %r0
 aghi    %r1, -24
 la      %r0, 168(%r1)
 lgr     %r3, %r0
 nill    %r3, 65520
 lgr     %r15, %r1
 lgr     %r0, %r15
 lgr     %r1, %r0
 aghi    %r1, -24
 la      %r0, 168(%r1)
 lgr     %r4, %r0
 nill    %r4, 65520
 lgr     %r15, %r1
 mvghi   8(%r4), 0
 mvghi   0(%r4), 0
 mvghi   8(%r3), 1
 mvghi   0(%r3), 0
 lg      %r0, 0(%r3)
 lg      %r1, 8(%r3)
 lg      %r5, 0(%r4)
 lg      %r4, 8(%r4)
 stg     %r4, 200(%r11)
 stg     %r5, 192(%r11)
 stg     %r1, 216(%r11)
 stg     %r0, 208(%r11)
 la      %r0, 224(%r11)
 la      %r1, 208(%r11)
 la      %r4, 192(%r11)
 stg     %r2, 184(%r11)
 lgr     %r2, %r0
 stg     %r3, 176(%r11)
 lgr     %r3, %r1
 brasl   %r14, __ashrti3@PLT
 lg      %r0, 224(%r11)
 lg      %r1, 232(%r11)
 lg      %r2, 184(%r11)
 stg     %r1, 8(%r2)
 stg     %r0, 0(%r2)
 lg      %r0, 8(%r2)
 lg      %r1, 0(%r2)
 stg     %r0, 168(%r11)
 stg     %r1, 160(%r11)
 j       .LBB0_1
.LBB0_1:
 lg      %r1, 176(%r11)
 lg      %r0, 8(%r1)
 lg      %r2, 0(%r1)
 lg      %r3, 160(%r11)
 xgr     %r3, %r2
 lg      %r2, 168(%r11)
 xgr     %r2, %r0
 ogr     %r2, %r3
 cghi    %r2, 0
 je      .LBB0_3
 j       .LBB0_2
.LBB0_2:
 larl    %r2, .Lbyte_str.2
 larl    %r4, .Lbyte_str.1
 lghi    %r3, 14
 brasl   %r14, std::panicking::begin_panic@PLT
 j       .Ltmp9+2
.LBB0_3:
 lmg     %r11, %r15, 328(%r11)
 br      %r14
```

cc @rkruppe 

Who maintains Rust's SystemZ support?