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From: "saitofuyuki at jamstec dot go.jp" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libfortran/108937] New: Intrinsic IBITS(I,POS,LEN) fails when
 LEN equals to BIT_SIZE(I).
Date: Mon, 27 Feb 2023 01:43:08 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108937

            Bug ID: 108937
           Summary: Intrinsic IBITS(I,POS,LEN) fails when LEN equals to
                    BIT_SIZE(I).
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libfortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: saitofuyuki at jamstec dot go.jp
  Target Milestone: ---

Created attachment 54539
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D54539&action=3Dedit
A minimum patch to fix ibits().

gfc_conv_intrinsic_ishft(), e.g, in gcc/fortran/trans-intrinsic.cc
catches a special case when shift widths GE BIT_SIZE at LSHIFT_EXPR
operation, which is not performed in gfc_conv_intrinsic_ibits.

I attached a minimum patch, and also a test program.

The output of the program before/after patch are as follow:

------------------------ before patch
IBITS(-1,0,32)
intrinsic 0 00000000000000000000000000000000
expected -1 11111111111111111111111111111111

------------------------ after patch
IBITS(-1,0,32)
intrinsic -1 11111111111111111111111111111111
expected -1 11111111111111111111111111111111

As far as I checked, this is a long-standing bug.  At least gfortran
10.4.0, 11.3.0, 12.2.0, and the latest one
(4341106354c6a463ce3628a4ef9c1a1d37193b59).=