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From: "luoxhu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/100085] Bad code for union transfer from __float128 to
 vector types
Date: Wed, 02 Jun 2021 08:27:37 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100085

--- Comment #9 from luoxhu at gcc dot gnu.org ---
Patch sent, it could fix the __float128 to vector __int128 issue,=20

https://gcc.gnu.org/pipermail/gcc-patches/2021-June/571689.html


But for __float128 to __int128 mentioned in #c4, need hack
rs6000_modes_tieable_p
to remove the stack operation in dse1. But I am not sure this is *LEGAL* si=
nce
TImode is allocated to GPR, It seems not true to access TImode from ALTIVEC=
 or
VSX without copying?

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index ad11b67b125..ee69463ac46 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -1974,6 +1974,9 @@ rs6000_modes_tieable_p (machine_mode mode1, machine_m=
ode
mode2)
       || mode2 =3D=3D PTImode || mode2 =3D=3D OOmode || mode2 =3D=3D XOmod=
e)
     return mode1 =3D=3D mode2;

+  if (mode1 =3D=3D TImode && ALTIVEC_OR_VSX_VECTOR_MODE (mode2))
+    return true;
+


        xxpermdi %vs0,%vs34,%vs34,3
        mfvsrd %r4,%vs34
        mfvsrd %r3,%vs0=