[Bug target/93768] New: Use vpternlog for composite logical operations

[rth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93768

            Bug ID: 93768
           Summary: Use vpternlog for composite logical operations
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rth at gcc dot gnu.org
  Target Milestone: ---

We should pattern-match multiple logical operations
into the ternary logical operator.  While there are
lots of obscure combinations available, probably the
most useful are

  Two-input inverted logicals:
  0x11  ~(B|C)
  0x77  ~(B&C)
  0x99  ~(B^C)
  0xbb  C|~B
  0xdd  B|~C

  Three-input simple logicals:
  0x80  A&B&C
  0x96  A^B^C
  0xfe  A|B|C

  Multiple alternatives of the ?: operation, which allows
  the memory-capable operand, C, in various positions, and
  allows the input-output operand, A, in various positions:
  0xe2  B?A:C
  0xe4  C?A:B
  0xb8  B?C:A
  0xd8  C?B:A
  0xca  A?B:C
  0xac  A?C:B