[Bug rtl-optimization/99376] New: Sanitizer detects undefined behaviour in rtlanal.c compiling ada

[Bug rtl-optimization/99376] New: Sanitizer detects undefined behaviour in rtlanal.c compiling ada

[zeccav at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99376

            Bug ID: 99376
           Summary: Sanitizer detects undefined behaviour in rtlanal.c
                    compiling ada
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zeccav at gmail dot com
  Target Milestone: ---

Needs option -O2

-- /home/vitti/gcc-150221-full-undefined/gcc/xgcc -S
-B/home/vitti/gcc-150221-full-undefined/gcc/
-I/home/vitti/gcc-150221-full-undefined/gcc/testsuite/ada/acats/support
~/f95/ada1.adb -O2

-- ../../gcc-150221/gcc/rtlanal.c:5060:35: runtime error: shift exponent 126 is
too large for 64-bit type 'long unsigned int'

-- rtlanal.c:5060 "nonzero &= ~((HOST_WIDE_INT_1U << result_low) - 1);"

WITH REPORT; USE REPORT;
PROCEDURE ada1 IS

     F : LONG_INTEGER;

     FUNCTION IDENT_LONG(A : LONG_INTEGER) RETURN LONG_INTEGER IS
     BEGIN
          IF EQUAL (3, 3) THEN
               RETURN A;
          ELSE
               RETURN 0;
          END IF;
     END IDENT_LONG;

     FUNCTION LONG_OK (X : LONG_INTEGER) RETURN BOOLEAN IS
     BEGIN
            return true;
     END;

BEGIN

     F := IDENT_LONG(LONG_INTEGER'FIRST);


     BEGIN
          IF LONG_OK (F*F) THEN
           return ;
          END IF;

     END;



END ada1;

[Bug rtl-optimization/99376] Sanitizer detects undefined behaviour in rtlanal.c compiling ada

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99376

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Blocks|                            |63426
   Last reconfirmed|                            |2021-03-04
                 CC|                            |bonzini at gnu dot org,
                   |                            |marxin at gcc dot gnu.org
             Status|UNCONFIRMED                 |NEW


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63426
[Bug 63426] [meta-bug] Issues found with -fsanitize=undefined

[Bug rtl-optimization/99376] Sanitizer detects undefined behaviour in rtlanal.c

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99376

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Sanitizer detects undefined |Sanitizer detects undefined
                   |behaviour in rtlanal.c      |behaviour in rtlanal.c
                   |compiling ada               |

--- Comment #1 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Nothing specific to Ada, it's

(mult:DI (reg:DI 87 [ _9 ])
    (reg:DI 87 [ _9 ]))

with (reg:DI 87) equal to LONG_MIN so low0 = low1 = 63.

Clearly a pair of tests against HOST_BITS_PER_WIDE_INT is missing in:

        if (result_width < mode_width)
          nonzero &= (HOST_WIDE_INT_1U << result_width) - 1;

        if (result_low > 0)
          nonzero &= ~((HOST_WIDE_INT_1U << result_low) - 1);

[Bug rtl-optimization/99376] Sanitizer detects undefined behaviour in rtlanal.c

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99376

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at gcc dot gnu.org      |ebotcazou at gcc dot gnu.org
             Status|NEW                         |ASSIGNED

[Bug rtl-optimization/99376] sanitizer detects undefined behaviour in rtlanal.c

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99376

--- Comment #2 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> Clearly a pair of tests against HOST_BITS_PER_WIDE_INT is missing in:
> 
> 	if (result_width < mode_width)
> 	  nonzero &= (HOST_WIDE_INT_1U << result_width) - 1;
> 
> 	if (result_low > 0)
> 	  nonzero &= ~((HOST_WIDE_INT_1U << result_low) - 1);

Actually only for result_low, as mode_width <= HOST_BITS_PER_WIDE_INT.

[Bug rtl-optimization/99376] sanitizer detects undefined behaviour in rtlanal.c

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99376

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Eric Botcazou <ebotcazou@gcc.gnu.org>:

https://gcc.gnu.org/g:28354bc22bd66648891a875ee08ca2b27debf2a2

commit r11-7521-g28354bc22bd66648891a875ee08ca2b27debf2a2
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Fri Mar 5 12:38:49 2021 +0100

    Fix undefined behavior spotted by the sanitizer

    gcc/
            PR rtl-optimization/99376
            * rtlanal.c (nonzero_bits1) <arithmetic operators>: If the number
            of low-order zero bits is too large, set the result to 0 directly.

[Bug rtl-optimization/99376] sanitizer detects undefined behaviour in rtlanal.c

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99376

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED
   Target Milestone|---                         |11.0

--- Comment #4 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
.