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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/95219] [11 Regression] FAIL:
 gcc.dg/vect/costmodel/x86_64/costmodel-pr30843.c
Date: Wed, 20 May 2020 06:36:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95219

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2020-05-20
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot =
gnu.org
   Target Milestone|---                         |11.0
             Status|UNCONFIRMED                 |ASSIGNED

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
I think this one is a bit older though (IIRC it was disabled before due to a
testsuite bug).  Vectorization _is_ clearly profitable - we're now using SLP
(possibly since that got induction support):

  Vector inside of loop cost: 24
  Vector prologue cost: 0
  Vector epilogue cost: 0
  Scalar iteration cost: 48
  Scalar outside cost: 0
  Vector outside cost: 0
  prologue iterations: 0
  epilogue iterations: 0
  Calculated minimum iters for profitability: 0

vectorized to

.L2:
        movdqa  %xmm0, %xmm4
        movdqa  %xmm1, %xmm3
        paddq   %xmm2, %xmm0
        addq    $32, %rdi
        movups  %xmm4, -32(%rdi)
        paddq   %xmm2, %xmm1
        movups  %xmm3, -16(%rdi)
        cmpq    %rdi, %rax
        jne     .L2

there's a missed optimization in that we choose two (identical) IVs for
the induction (late FRE is in "simple" mode and thus does not get rid of th=
ose
as equivalent) and that we have odd IVs (the extra moves), possibly
out-of-SSA cannot coalesce because of the constants:

  # vect_vec_iv_.7_1 =3D PHI <{ 0, 0 }(2), _19(3)>
  # vect_vec_iv_.8_18 =3D PHI <{ 0, 0 }(2), _17(3)>

and tricks maybe do not apply because of vector types.  I'll take this bug.=