[llvm-bugs] [Bug 23085] [AArch64] Useless register shuffling with tail-call

via llvm-bugs llvm-bugs at lists.llvm.org
Mon Jul 11 09:20:07 PDT 2016


John Brawn <john.brawn.123 at gmail.com> changed:

           What    |Removed                     |Added
             Status|NEW                         |RESOLVED
                 CC|                            |john.brawn.123 at gmail.com
         Resolution|---                         |FIXED

--- Comment #1 from John Brawn <john.brawn.123 at gmail.com> ---
Latest trunk clang produces:

foo:                                    // @foo
// BB#0:                                // %entry
    mov    w8, #20000
    cmp    w0, w8
    b.le    .LBB0_2
// BB#1:                                // %return
.LBB0_2:                                // %if.end
    add    w1, w0, w0, lsl #6
    mov    w0, wzr
    b    bar

Looking at the -debug output compared to a build from a year ago both
recognised that x should be allocated to w0, but previously we failed to do
that for some reason (-debug output just says "missed hint %W0") but now we
succeed. Anyway, this bug appears to have been fixed.

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