AMDGPU GlobalISel fails on select of G_UBSANTRAP

[arsenm]

https://godbolt.org/z/6PzeExK4f

; RUN: llc -mtriple=amdgcn-amd-amdhsa -global-isel < %s
; LLVM ERROR: cannot select: G_UBSANTRAP 0 (in function: ubsan_trap)

define void @ubsan_trap() {
  call void @llvm.ubsantrap(i8 0)
  ret void
}

We already handle G_TRAP and G_DEBUGTRAP. ubsan isn't particularly special and should be able to follow

[llvmbot]

Hi!

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[llvmbot]

@llvm/issue-subscribers-backend-amdgpu

Author: Matt Arsenault (arsenm)

https://godbolt.org/z/6PzeExK4f

; RUN: llc -mtriple=amdgcn-amd-amdhsa -global-isel < %s
; LLVM ERROR: cannot select: G_UBSANTRAP 0 (in function: ubsan_trap)

define void @<!-- -->ubsan_trap() {
  call void @<!-- -->llvm.ubsantrap(i8 0)
  ret void
}

We already handle G_TRAP and G_DEBUGTRAP. ubsan isn't particularly special and should be able to follow

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Matt Arsenault (arsenm)

https://godbolt.org/z/6PzeExK4f

; RUN: llc -mtriple=amdgcn-amd-amdhsa -global-isel < %s
; LLVM ERROR: cannot select: G_UBSANTRAP 0 (in function: ubsan_trap)

define void @<!-- -->ubsan_trap() {
  call void @<!-- -->llvm.ubsantrap(i8 0)
  ret void
}

We already handle G_TRAP and G_DEBUGTRAP. ubsan isn't particularly special and should be able to follow

[Filip-Nachov]

@arsenm hey can you provide a bit more info on this issue and assign me I would like to work on it

[arsenm]

@arsenm hey can you provide a bit more info on this issue and assign me I would like to work on it

The IR has 3 different types of traps. ubsantrap by default in the DAG is just replaced with trap:

llvm-project/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

Line 1125 in ecae8d0

case ISD::UBSANTRAP:

It's probably just a matter of adding G_UBSAN to one of these lists unconditionally lowering:

llvm-project/llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp

Line 2103 in ecae8d0

getActionDefinitionsBuilder({G_MEMCPY, G_MEMCPY_INLINE, G_MEMMOVE, G_MEMSET})

and adding the relevant tests.

If the underlying support code in LegalizerHelper is missing, it needs a new case to perform the G_UBSANTRAP -> G_TRAP substitution