[PATCH] D99674: [InstCombine] Conditionally fold select i1 into and/or

[Bjorn Pettersson via Phabricator via llvm-commits]

bjope added a comment.

I've seen problems with infinite loops in InstCombine after mergin this patch downstream:

  IC: Visiting:   %not. = xor <4 x i1> %271, <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: Visiting:   %274 = select <4 x i1> %not., <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, <4 x i1> %273, !dbg !252
  IC: ADD DEFERRED:   %not. = xor <4 x i1> %271, <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: Mod =   %274 = select <4 x i1> %not., <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, <4 x i1> %273, !dbg !252
      New =   %274 = select <4 x i1> %271, <4 x i1> %273, <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: ADD:   %274 = select <4 x i1> %271, <4 x i1> %273, <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: ERASE   %not. = xor <4 x i1> %271, <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: ADD DEFERRED:   %271 = and <4 x i1> %broadcast.splat2008, %270, !dbg !252
  IC: ADD:   %271 = and <4 x i1> %broadcast.splat2008, %270, !dbg !252
  IC: Visiting:   %271 = and <4 x i1> %broadcast.splat2008, %270, !dbg !252
  IC: Visiting:   %274 = select <4 x i1> %271, <4 x i1> %273, <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: ADD DEFERRED:   %not. = xor <4 x i1> %271, <i1 true, i1 true, i1 true, i1 true>
  IC: Old =   %274 = select <4 x i1> %271, <4 x i1> %273, <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
      New =   <badref> = select <4 x i1> %not., <4 x i1> <i1 true, i1 true, i1 true, i1 true>, <4 x i1> %273
  IC: ADD:   %274 = select <4 x i1> %not., <4 x i1> <i1 true, i1 true, i1 true, i1 true>, <4 x i1> %273, !dbg !252
  IC: ERASE   %275 = select <4 x i1> %271, <4 x i1> %273, <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: ADD DEFERRED:   %271 = and <4 x i1> %broadcast.splat2008, %270, !dbg !252
  IC: ADD DEFERRED:   %273 = icmp sge <4 x i32> %272, %broadcast.splat2010, !dbg !252
  IC: ADD:   %273 = icmp sge <4 x i32> %272, %broadcast.splat2010, !dbg !252
  IC: ADD:   %271 = and <4 x i1> %broadcast.splat2008, %270, !dbg !252
  IC: ADD:   %not. = xor <4 x i1> %271, <i1 true, i1 true, i1 true, i1 true>, !dbg !252
  IC: Visiting:   %not. = xor <4 x i1> %271, <i1 true, i1 true, i1 true, i1 true>, !dbg !252
  IC: Visiting:   %271 = and <4 x i1> %broadcast.splat2008, %270, !dbg !252
  IC: Visiting:   %273 = icmp sge <4 x i32> %272, %broadcast.splat2010, !dbg !252
  IC: Visiting:   %274 = select <4 x i1> %not., <4 x i1> <i1 true, i1 true, i1 true, i1 true>, <4 x i1> %273, !dbg !252
  IC: Visiting:   %predphi = select <4 x i1> %274, <4 x i32> %281, <4 x i32> <i32 poison, i32 poison, i32 poison, i32 0>, !dbg !252
  IC: Visiting:   %282 = extractelement <4 x i32> %predphi, i32 3
  IC: ADD DEFERRED:   %not. = xor <4 x i1> %271, <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: ADD DEFERRED:   %274 = select <4 x i1> %not., <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, <4 x i1> %273, !dbg !252
  IC: ADD DEFERRED:   %predphi = select <4 x i1> %274, <4 x i32> %281, <4 x i32> <i32 poison, i32 poison, i32 poison, i32 0>, !dbg !252
  IC: Mod =   %282 = extractelement <4 x i32> %predphi, i32 3
      New =   %282 = extractelement <4 x i32> %predphi, i32 3
  IC: ADD:   %282 = extractelement <4 x i32> %predphi, i32 3
  IC: ADD:   %predphi = select <4 x i1> %274, <4 x i32> %281, <4 x i32> <i32 poison, i32 poison, i32 poison, i32 0>, !dbg !252
  IC: ADD:   %274 = select <4 x i1> %not., <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, <4 x i1> %273, !dbg !252
  IC: ADD:   %not. = xor <4 x i1> %271, <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: Visiting:   %not. = xor <4 x i1> %271, <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: Visiting:   %274 = select <4 x i1> %not., <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, <4 x i1> %273, !dbg !252
  IC: ADD DEFERRED:   %not. = xor <4 x i1> %271, <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: Mod =   %274 = select <4 x i1> %not., <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, <4 x i1> %273, !dbg !252
      New =   %274 = select <4 x i1> %271, <4 x i1> %273, <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: ADD:   %274 = select <4 x i1> %271, <4 x i1> %273, <4 x i1> <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: ERASE   %not. = xor <4 x i1> %271, <i1 poison, i1 poison, i1 poison, i1 true>, !dbg !252
  IC: ADD DEFERRED:   %271 = and <4 x i1> %broadcast.splat2008, %270, !dbg !252
  ...

Working on reducing the test case a bit, and if I can find a reproducer for the main trunk then I think we need to revert this patch.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D99674/new/

https://reviews.llvm.org/D99674