[PATCH] D110603: [GlobalISel][IRTranslator] Emit trap intrinsic for unreachable

[Mikael Holmén via Phabricator via llvm-commits]

uabelho added a comment.

Hi,

I think there is something broken after the relanding of this.
For my out-of-tree target I have a testcase where there exists a block that is unreachable from entry, but that is referenced in a PHI:

  body: |
    bb.0:
      liveins: $a0h, $r0
      %0:all(s16) = COPY $a0h
      %1:all(s16) = COPY $r0
      brr_uncond %bb.2
  
    bb.1:
      brr_uncond %bb.2
  
    bb.2:
      %2:all(s16) = G_PHI %0(s16), %bb.0, %1(s16), %bb.1
      $a0h = COPY %2

So %bb.1 is dead, but jumps to %bb.2 so the G_PHI in %bb.2 references %bb.1

With this patch we get this result:

  body:             |
    ; Instruction count: 5
    bb.0:
      successors: %bb.2(0x80000000)
      liveins: $a0h, $r0
    
      %0:anh_rn = COPY $a0h
      %1:anh_rn = COPY $r0
      brr_uncond %bb.2
    
    bb.2:
      %2:anh_rn = PHI %0, %bb.0, %1, %bb.-1
      $a0h = COPY %2

So %bb.1 is removed, but the PHI now looks broken because %bb.1 has been replace with %bb.-1 instead of the operand being removed completely.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D110603/new/

https://reviews.llvm.org/D110603