[Bug c/102245] New: false int-in-bool-context warning with shift

[Bug c/102245] New: false int-in-bool-context warning with shift

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

            Bug ID: 102245
           Summary: false  int-in-bool-context warning with shift
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
#define shiftCB_DISABLE_FAULT_ON_UNMAPPED_ACCESS1 0
#define maskCB_DISABLE_FAULT_ON_UNMAPPED_ACCESS1 1L

#define REG_FIELD_MASK(a,b) (mask##b)
#define REG_FIELD_SHIFT(a,b) (shift##b)

#define REG_SET_FIELD(orig_val, reg, field, field_val)                  \
        (((orig_val) & ~REG_FIELD_MASK(reg, field)) |                   \
         (REG_FIELD_MASK(reg, field) & ((field_val) << REG_FIELD_SHIFT(reg,
field))))



int f(_Bool enable)
{
  int tmp = 0;
  tmp = REG_SET_FIELD(tmp, VM_PRT_CNTL,
                      CB_DISABLE_FAULT_ON_UNMAPPED_ACCESS1,
                      enable);
  return tmp;
}

------ CUT ----
Compile this on an ILP32 target with "-W -Wall -O2 -Werror
-Werror=int-in-bool-context" and you get:
<source>: In function 'f':
<source>:10:53: error: '<<' in boolean context, did you mean '<'?
[-Werror=int-in-bool-context]
   10 |          (REG_FIELD_MASK(reg, field) & ((field_val) <<
REG_FIELD_SHIFT(reg, field))))
      |                                       
~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<source>:17:9: note: in expansion of macro 'REG_SET_FIELD'
   17 |   tmp = REG_SET_FIELD(tmp, VM_PRT_CNTL,
      |         ^~~~~~~~~~~~~
cc1: all warnings being treated as errors


This is not correct as the shift is correct, I want to do a shift by 0 here and
there is no boolean context at all. And it does not warn with LP64 targets
either.

[Bug c/102245] false int-in-bool-context warning with shift

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I should mention this was reduced from drivers/gpu/drm/amd/amdgpu/gmc_v6_0.c in
the Linux kernel compiling for arm-linux-gnueabi but can reproduce the warning
on x86_64 with -m32 option.

[Bug c/102245] false int-in-bool-context warning with shift

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So this is a regression only on the trunk.

[Bug c/102245] [12 Regression] false int-in-bool-context warning with shift

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |12.0
            Summary|false  int-in-bool-context  |[12 Regression] false
                   |warning with shift          |int-in-bool-context warning
                   |                            |with shift

[Bug c/102245] [12 Regression] false int-in-bool-context warning with shift

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-09-08
             Status|UNCONFIRMED                 |NEW
                 CC|                            |jakub at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Started with r12-3073-g1d244020246cb155e4de62ca3b302b920a1f513f
Deobfuscated testcase:
int
foo (_Bool x)
{
  int v = 0;
  return (v & ~1L) | (1L & (x << 0));
}

[Bug c/102245] [12 Regression] false int-in-bool-context warning with shift

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
So, seems the binary context is result of shorten_binary_op, we see the
1L and (((int)x) << 0) operands of BIT_AND_EXPR, result_type is therefore long
int and shorten_binary_op uses convert to convert that (((int)x) << 0) to long
int and triggers the match.pd rule and folds it into (long int)x (where x has
_Bool type).
shorten_binary_op then decides to return _Bool type, which is why we have the
bool context.

[Bug c/102245] [12 Regression] false int-in-bool-context warning with shift

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
I think the warning should work on unfolded (un-narrowed) trees or
shorten_binary_op should from a INTEGER_TYPEd operation not create a
BOOLEAN_TYPEd one (but maybe simply build a unsigned int:1 for it)?

[Bug c/102245] [12 Regression] false int-in-bool-context warning with shift

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Here is a testcase which will hit the warning on all targets and not just ILP32
specific ones:
int
foo (_Bool x)
{
  int v = 0;
  return (v & ~1u) | (1u & (x << 0));
}

[Bug c/102245] [12 Regression] false int-in-bool-context warning with shift

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |roger at nextmovesoftware dot com
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |roger at nextmovesoftware dot com

--- Comment #7 from Roger Sayle <roger at nextmovesoftware dot com> ---
Patch proposed:
https://gcc.gnu.org/pipermail/gcc-patches/2021-September/579293.html

[Bug c/102245] [12 Regression] false int-in-bool-context warning with shift

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

--- Comment #8 from Roger Sayle <roger at nextmovesoftware dot com> ---
Alternate patch proposed:
https://gcc.gnu.org/pipermail/gcc-patches/2021-September/579378.html

[Bug c/102245] [12 Regression] false int-in-bool-context warning with shift

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:

https://gcc.gnu.org/g:2578a3870ef849dc77e98796600181b64ae4fd61

commit r12-3623-g2578a3870ef849dc77e98796600181b64ae4fd61
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Fri Sep 17 15:57:34 2021 +0100

    PR c/102245: Disable sign-changing optimization for shifts by zero.

    Respecting Jakub's suggestion that it may be better to warn-on-valid for
    "if (x << 0)" as the author might have intended "if (x < 0)" [which will
    also warn when x is _Bool], the simplest way to resolve this regression
    is to disable the recently added fold transformation for shifts by zero;
    these will be optimized later (elsewhere).  Guarding against integer_zerop
    is the simplest of three alternatives; the second being to only apply
    this transformation to GIMPLE and not GENERIC, and the third (potentially)
    being to explicitly handle shifts by zero here, with an (if cond then
else),
    optimizing the expression to a convert, but awkwardly duplicating a
    more general transformation earlier in match.pd's shift simplifications.

    2021-09-17  Roger Sayle  <roger@nextmovesoftware.com>

    gcc/ChangeLog
            PR c/102245
            * match.pd (shift optimizations): Disable recent sign-changing
            optimization for shifts by zero, these will be folded later.

    gcc/testsuite/ChangeLog
            PR c/102245
            * gcc.dg/Wint-in-bool-context-4.c: New test case.

[Bug c/102245] [12 Regression] false int-in-bool-context warning with shift

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102245

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #10 from Roger Sayle <roger at nextmovesoftware dot com> ---
Fixed on mainline.