[AMDGPU] Backend crash from 'waitcnt overflow'

[jhuber6]

The following LLVM-IR crashes the AMDGPU backend due to a waitcnt overflow. This has just started happening in the past day or so. A reproducer can also be used here https://godbolt.org/z/d59Y7o3dz.

target triple = "amdgcn-amd-amdhsa"

declare fastcc void @bar()

define fastcc i32 @foo() #0 {
  fence acquire
  call fastcc void @bar()
  br label %1

1:
  br label %1
}

attributes #0 = { "target-cpu"="gfx1030" }

[llvmbot]

@llvm/issue-subscribers-backend-amdgpu

Author: Joseph Huber (jhuber6)

The following LLVM-IR crashes the AMDGPU backend due to a waitcnt overflow. This has just started happening in the past day or so. A reproducer can also be used here https://godbolt.org/z/d59Y7o3dz.

target triple = "amdgcn-amd-amdhsa"

declare fastcc void @<!-- -->bar()

define fastcc i32 @<!-- -->foo() #<!-- -->0 {
  fence acquire
  call fastcc void @<!-- -->bar()
  br label %1

1:
  br label %1
}

attributes #<!-- -->0 = { "target-cpu"="gfx1030" }

[jayfoad]

Bisected to 16945bc (#77439).