Test for repr-transparent-aggregates-1.rs fails cross-compiling wasm32-unknown-unknown with LLVM 11.0

[sundbry]

This test fails on rust-1.49 cross compiling wasm32-unknown-unknown with LLVM 11.0. It looks like the intermediate representation for a void function has significantly changed from what is expected (see attached .ll file).

repr-transparent-aggregates-1.ll
Guix Build log rust-1.49.0.drv.txt.gz

Actual code generated for test_BigS:

; Function Attrs: nounwind
define %BigS @test_BigS(%BigS %0) unnamed_addr #0 {
start:
  %1 = alloca %BigS, align 4
  %_1 = alloca %BigS, align 4
  store %BigS %0, %BigS* %_1, align 4
  br label %bb1

bb1:                                              ; preds = %bb1, %start
  call void @llvm.sideeffect()
  br label %bb1
}

Error (expected function signature):

/tmp/guix-build-rust-1.49.0.drv-0/rustc-1.49.0-src/src/test/codegen/repr-transparent-aggregates-1.rs:37:11: error: CHECK: expected string not found in input
// CHECK: define void @test_BigS(%BigS* [[BIGS_RET_ATTRS:.*]], %BigS* [[BIGS_ARG_ATTRS1:.*]] byval(%BigS) [[BIGS_ARG_ATTRS2:.*]])
          ^
/tmp/guix-build-rust-1.49.0.drv-0/rustc-1.49.0-src/build/x86_64-unknown-linux-gnu/test/codegen/repr-transparent-aggregates-1/repr-transparent-aggregates-1.ll:1:1
: note: scanning from here
; ModuleID = 'repr_transparent_aggregates_1.3a1fbbbh-cgu.0'
^
/tmp/guix-build-rust-1.49.0.drv-0/rustc-1.49.0-src/build/x86_64-unknown-linux-gnu/test/codegen/repr-transparent-aggregates-1/repr-transparent-aggregates-1.ll:16:
1: note: possible intended match here
define %BigS @test_BigS(%BigS %0) unnamed_addr #0 {

Related discussion regarding unstable IR code gen: #74396 (comment)

[Enselic]

Triage: What are the commands to reproduce the ICE? I tried this, but I'm probably doing something wrong:

curl -JLO https://raw.githubusercontent.com/rust-lang/rust/582071c1ebd5ec19ded8648223e9108b5ce65d85/src/test/codegen/repr-transparent-aggregates-1.rs
rustup install nightly-2021-01-26
rustup target add wasm32-unknown-unknown --toolchain nightly-2021-01-26
rustc +nightly-2021-01-26 repr-transparent-aggregates-1.rs --target wasm32-unknown-unknown