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From: "manolis.tsamis at vrull dot eu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/112415] [14 regression] Python 3.11
 miscompiled on HPPA with new RTL fold mem offset pass, since
 r14-4664-g04c9cf5c786b94
Date: Mon, 13 Nov 2023 13:20:01 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112415

--- Comment #46 from Manolis Tsamis <manolis.tsamis at vrull dot eu> ---
I have reproduced the segfault with f-m-o limited to only fold insn 272 from
compiler_call_helper. The exact transformation is:

Memory offset changed from 0 to 388 for instruction:
(insn 273 272 276 30 (set (mem:SI (reg/f:SI 22 %r22 [478]) [4 MEM[(intD.1
*)_107 + 388B]+0 S4 A32])
        (reg:SI 14 %r14 [orig:167 vect_pretmp_36.2448D.32932 ] [167]))
"Python/compile.c":5970:20 42 {*pa.md:2193}
     (nil))
deferring rescan insn with uid =3D 273.
Instruction folded:(insn 272 269 273 30 (set (reg/f:SI 22 %r22 [478])
        (plus:SI (reg/f:SI 19 %r19 [orig:127 prephitmp_37 ] [127])
            (const_int 388 [0x184]))) "Python/compile.c":5970:20 120 {addsi=
3}
     (nil))

This instruction is also included to the ones that Dave mentioned. Again, if
I'm missing something as to why this transformation is illegal please tell =
me.
Given these are also consecutive instructions, I'm just seeing here that=20

%r22 =3D %r19 + 388
[%r22] =3D %r14

is transformed to

%r22 =3D %r19
[%r22 + 388] =3D %r14

I haven't tracked all other uses of %r22 yet, but in theory if there was any
non-foldable use of that register then the transformation wouldn't be made.

Manolis=