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From: "jcmvbkbc at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/108919] New: pure nested function may clobber its static
 chain pointer in windowed ABI on xtensa
Date: Fri, 24 Feb 2023 08:52:09 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108919

            Bug ID: 108919
           Summary: pure nested function may clobber its static chain
                    pointer in windowed ABI on xtensa
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jcmvbkbc at gcc dot gnu.org
  Target Milestone: ---

Created attachment 54525
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D54525&action=3Dedit
test.c

The following gfortran tests fail on windowed ABI xtensa target, but pass on
call0 ABI:

gfortran.dg/character_workout_1.f90   -O[123s]  execution test
gfortran.dg/character_workout_4.f90   -O[123s]  execution test

E.g. gfortran.dg/character_workout_1.f90 -O1 ends with the message 'STOP 20=
9'.

This happens because in these tests pure nested functions are generated for
subroutines achar_cm and achar_am and the fwprop1 pass removes static chain
pointer initialization between the calls to these functions:

.L143:=20=20
        addi    a3, sp, 108
        movi    a4, 0xd4
        add.n   a4, sp, a4
        addi    a8, sp, -20
        s32i.n  a4, a8, 0
        movi.n  a11, 7
        mov.n   a10, a3
        call8   achar_cm.21
        movi.n  a11, 7
        mov.n   a10, a3
        call8   achar_am.15

Windowed ABI for xtensa specifies that the static chain is passed on the st=
ack,
at offset -20 from the called function's CFA, i.e. outside the caller's sta=
ck
frame. This location may be overwritten if the called function makes functi=
on
calls that exceed certain depth.

The issue may be reproduced with the attached small test case.=