library compilation problem on s390x

[pazolka]

I'm getting the following error when building Parity Ethereum:

LLVM ERROR: Cannot select: 0x3ff58cd1598: i32 = SystemZISD::GET_CCMASK 0x3ff58cd13f8, Constant:i32<15>, Constant:i32<3>
  0x3ff58cd13f8: i32 = srl 0x3ff58a47040, Constant:i32<31>
    0x3ff58a47040: i32 = add 0x3ff58cd1a10, Constant:i32<-536870912>
      0x3ff58cd1a10: i32 = SystemZISD::IPM 0x3ff58cd1870:1
        0x3ff58cd1870: i64,i32 = SystemZISD::USUBO 0x3ff58cd12c0, Constant:i64<1>
          0x3ff58cd12c0: i64,ch = CopyFromReg 0x3ff58837308, Register:i64 %1
            0x3ff58a46f70: i64 = Register %1
          0x3ff58cd1f90: i64 = Constant<1>
      0x3ff58cd18d8: i32 = Constant<-536870912>
    0x3ff589c8260: i32 = Constant<31>
  0x3ff58cd1c80: i32 = Constant<15>
  0x3ff589c8740: i32 = Constant<3>
In function: _ZN15primitive_types4U12814saturating_sub17haa8aa831da279cf8E
error: Could not compile `primitive-types`.
warning: build failed, waiting for other jobs to finish...
error: build failed

Rust version: 1.34.2

[nikita-fuchs]

The source can be found here: https://bitbucket.org/nikita-fuchs/parity-ring-removal/src/master/

It is a fork of https://github.com/paritytech/parity-ethereum with two libraries removed that are not supported on s390x architecture. The forked code compiles just fine on x64.

[mati865]

Was the Rust installed with official package (rustup, installers) or using Linux package manager?

[pazolka]

Rustup

[mati865]

https://reviews.llvm.org/D59822 should fix it.
I'll see if I can reproduce it by cross compilation and prepare backports.

[mati865]

I can reproduce it by cross compiling from x86_64 and unfortunately backporting https://reviews.llvm.org/D59822 did not solve the issue.
https://github.com/paritytech/parity-common/tree/9d2de86e70f8e84358d0819a92666acb4f6ab9c4/primitive-types is what exposes this LLVM bug and can be used as smaller repro.

[nikic]

@mati865 Can you provide the --emit=llvm-ir output from primitive-types?

[mati865]

@nikic I think it's too big to be useful but here you go:
IR.zip

Obtained with: CARGO_INCREMENTAL=0 cargo rustc --target s390x-unknown-linux-gnu --release -- -o ir --emit=llvm-ir -C codegen-units=1 -C debuginfo=0 -C panic=abort

[nikic]

Bugpoint reduced:

; ModuleID = '<stdin>'
source_filename = "primitive_types.arilfrs7-cgu.0"
target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-a:8:16-n32:64"
target triple = "s390x-unknown-linux-gnu"

define void @_ZN15primitive_types4U51211checked_sub17h5ff0d8bcee5c2f13E() unnamed_addr #0 {
start:
  %_5.sroa.4.0.copyload = load i64, i64* undef, align 8
  %0 = tail call { i64, i1 } @llvm.usub.with.overflow.i64(i64 undef, i64 %_5.sroa.4.0.copyload) #2
  %1 = extractvalue { i64, i1 } %0, 1
  %2 = zext i1 %1 to i8
  br i1 undef, label %bb21.i, label %bb34.i

bb21.i:                                           ; preds = %start
  %3 = tail call { i64, i1 } @llvm.usub.with.overflow.i64(i64 undef, i64 1) #2
  %4 = extractvalue { i64, i1 } %3, 1
  %5 = zext i1 %4 to i8
  %6 = add nuw nsw i8 %5, %2
  br label %bb34.i

bb34.i:                                           ; preds = %bb21.i, %start
  %carry.1.in.i = phi i8 [ %6, %bb21.i ], [ %2, %start ]
  ret void
}

; Function Attrs: nounwind readnone speculatable
declare { i64, i1 } @llvm.usub.with.overflow.i64(i64, i64) #1

attributes #0 = { "target-features"="-vector" }
attributes #1 = { nounwind readnone speculatable }
attributes #2 = { nounwind }

!llvm.module.flags = !{!0}

!0 = !{i32 2, !"RtLibUseGOT", i32 1}

[nikic]

LLVM bug report: https://bugs.llvm.org/show_bug.cgi?id=42512

[nikic]

Fixed upstream via llvm/llvm-project@a2a09cb.

[nikita-fuchs]

Thank you @nikic , what does that mean for our case? As I'm not particularly familiar with LLVM and it came bundled with rust anyway I think, how do we obtain the latest fix? Just manually install/upgrade LLVM ?