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From: "luoxhu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/106069] [12/13 Regression] wrong code with -O
 -fno-tree-forwprop -maltivec on ppc64le
Date: Tue, 26 Jul 2022 06:28:47 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106069

--- Comment #16 from luoxhu at gcc dot gnu.org ---
The attached files are all built with -mcpu=3Dpower8 and the case also fail=
s on
P8LE.
Also I verified the code produces expected output on P8BE. ('Aborted' is ca=
used
by BE returns 0x41 instead of 0x98 for LE.)

P8LE &P9LE:

luoxhu@gcc135 build $ ./q.bad
B0: 0, 0,0,0
Aborted

P8BE:
luoxhu@gcc203:~/workspace/build$ ./q.bad
B0: 41fcef98, 91648e8b,7dca18c6,61707865
Aborted


P8BE seems generates better code with the patch:

luoxhu@gcc203:~/workspace/build$ diff q.good.S q.bad.S -U5
--- q.good.S    2022-07-26 09:19:32.487216946 +0300
+++ q.bad.S     2022-07-26 09:15:58.006770996 +0300
@@ -1,6 +1,7 @@
        .file   "q.C"
+       .machine power8
        .section        ".text"
        .section        .rodata.str1.8,"aMS",@progbits,1
        .align 3
 .LC0:
        .string "B0: %x, %x,%x,%x\n"
@@ -24,19 +25,17 @@
        .cfi_def_cfa_offset 128
        .cfi_offset 65, 16
        .cfi_offset 30, -16
        .cfi_offset 31, -8
        mr %r30,%r3
-       vmrghw %v2,%v2,%v4
-       vmrghw %v5,%v3,%v5
-       vmrghw %v5,%v2,%v5
-       vspltw %v0,%v5,3
+       vspltw %v0,%v5,0
        mfvsrwz %r7,%vs32
-       vspltw %v0,%v5,2
+       vspltw %v0,%v4,0
        mfvsrwz %r6,%vs32
-       mfvsrwz %r5,%vs37
-       vspltw %v0,%v5,0
+       vspltw %v0,%v3,0
+       mfvsrwz %r5,%vs32
+       vspltw %v0,%v2,0
        mfvsrwz %r31,%vs32
        rldicl %r7,%r7,0,32
        rldicl %r6,%r6,0,32
        rldicl %r5,%r5,0,32
        rldicl %r4,%r31,0,32
@@ -169,6 +168,6 @@
        .set    .LANCHOR1,. + 0
        .type   res, @object
        .size   res, 1
 res:
        .zero   1
-       .ident  "GCC: (Debian 9.5.0-1) 9.5.0"
+       .ident  "GCC: (GNU) 13.0.0 20220726 (experimental)"=