[Bug target/117169] New: Missed opportunity to combine sign and bitmask tests

[rsandifo at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117169
            Bug ID: 117169
           Summary: Missed opportunity to combine sign and bitmask tests
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rsandifo at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64*-*-*

int f1(int x) { return x < 0 || x & 3; }

on aarch64 produces:

f1:
        tbnz    w0, #31, .L3
        tst     x0, 3
        cset    w0, ne
        ret
.L3:
        mov     w0, 1
        ret

But this could be a single TST.  Clang produces:

f1:
        tst     w0, #0x80000003
        cset    w0, ne
        ret

GCC does produce single bitmask tests for non-sign tests, such as:

int f2(int x) { return x & 0x100 || x & 3; }

but of course:

int f3(int x) { return x & 0x80000000 || x & 3; }

is canonicalised to the original form.