[InstCombine] samesign flag should be dropped

[dtcxzyw]

Reproducer:

define i1 @src(i64 %x, i64 %y, i1 %cond) {
  %cmp1 = icmp ult i64 %x, %y
  %cmp2 = icmp samesign uge i64 %x, %y
  %sel = select i1 %cond, i1 %cmp1, i1 %cmp2
  ret i1 %sel
}

define i1 @tgt(i64 %x, i64 %y, i1 %cond) {
  %cmp2 = icmp samesign uge i64 %x, %y
  %sel = xor i1 %cond, %cmp2
  ret i1 %sel
}

[antoniofrighetto]

Don't we miss checking the flag in hasPoisonGeneratingFlags?

[dtcxzyw]

Don't we miss checking the flag in hasPoisonGeneratingFlags?

Yeah. I am preparing a patch.

[dtcxzyw]

But adding support in hasPoisonGeneratingFlags doesn't address this issue :(

[antoniofrighetto]

But adding support in hasPoisonGeneratingFlags doesn't address this issue :(

I assume we may need to dropPoisonGeneratingFlags in InstCombineCompares, where needed?