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From: "xry111 at mengyan1223 dot wang" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/104842] New: mips: signed overflow in LUI_OPERAND
Date: Tue, 08 Mar 2022 16:54:24 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104842

            Bug ID: 104842
           Summary: mips: signed overflow in LUI_OPERAND
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: xry111 at mengyan1223 dot wang
  Target Milestone: ---

Found this building GCC on mips64el-linux-gnuabi64 with bootstrap-ubsan
(testing a patch enabling ubsan for mips64*-linux-gnu*):

../../gcc/gcc/config/mips/predicates.md:382:11: runtime error: signed integ=
er
overflow: 9223372036854775807 + 65536 cannot be represented in type 'long=
=20=20=20=20
int'

That line uses LUI_INT (x), which expands to LUI_OPERAND (INTVAL (x)).=20
LUI_OPERAND is defined as:

#define LUI_OPERAND(VALUE) \
  (((VALUE) | 0x7fff0000) =3D=3D 0x7fff0000 \
   || ((VALUE) | 0x7fff0000) + 0x10000 =3D=3D 0)

Obviously this will cause a signed overflow when INTVAL (x) is, for example,
the maximum value of HOST_WIDE_INT.=