Missed transform: (a & !b) ? a : b into a | b

[Kmeakin]

godbolt, alive

#include <stdbool.h>

bool src(bool a, bool b) { return (a & !b) ? a : b; }
bool tgt(bool a, bool b) { return a | b; }

define i1 @src(i1 %0, i1 %1){
  %3 = xor i1 %1, true
  %4 = and i1 %3, %0
  %5 = select i1 %4, i1 %0, i1 %1
  ret i1 %5
}

define i1 @tgt(i1 %0, i1 %1){
  %3 = or i1 %0, %1
  ret i1 %3
}

Note that the x864-64 backend is able to optimise src into tgt, but AArch64 and RISCV are not, so there is probably a missind DAG combine too

[llvmbot]

@llvm/issue-subscribers-backend-aarch64

[llvmbot]

@llvm/issue-subscribers-backend-risc-v

[dtcxzyw]

Generalized transform: https://alive2.llvm.org/ce/z/x8ZSY9

[dtcxzyw]

Candidate patch: https://reviews.llvm.org/D158983