[Bug c++/97255] New: Vectorizer gives a boolean a value of 255

[Bug c++/97255] New: Vectorizer gives a boolean a value of 255

[iwans at xilinx dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97255

            Bug ID: 97255
           Summary: Vectorizer gives a boolean a value of 255
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: iwans at xilinx dot com
  Target Milestone: ---

Created attachment 49292
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49292&action=edit
Minimal file demonstrating bug

Here is a godbolt link demonstrating the bug: https://godbolt.org/z/jK8Wsz

The following function with -O3 assigns a value of 255 to variables in the out
array. Building with -O3 -fno-tree-vectorize allows the code to execute
correctly 

void
logicalOr(Array< char, 4 > in1[60], 
    Array< bool, 4 > out[60])
{
    for (unsigned k0 = 0u; k0 < 60u; ++k0) {
        Array< char, 4 > in1m = in1[k0];
        Array< bool, 4 > x;
        for (unsigned k1 = 0u; k1 < 4u; ++k1) {
            char in1s = in1m[k1];
            x[k1] = in1s != char(0) || in1s != char(0);
        }
        out[k0] = x;
    }
}


build the attached cpp file (it has no #includes) with 

(Buggy)
gcc -O3 vectorizedBool.cpp
./a.out
echo $? // correct value is 1. Actually returns 255

(Not buggy)
gcc -O3 -fno-tree-vectorize vectorizedBool.cpp 
./a.out
echo $? // correct value is 1. returns 1

Here is some output from -v

COLLECT_GCC=/opt/compiler-explorer/gcc-10.2.0/bin/g++

Target: x86_64-linux-gnu

Configured with: ../gcc-10.2.0/configure
--prefix=/opt/compiler-explorer/gcc-build/staging --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu --disable-bootstrap
--enable-multiarch --with-abi=m64 --with-multilib-list=m32,m64,mx32
--enable-multilib --enable-clocale=gnu
--enable-languages=c,c++,fortran,ada,go,d --enable-ld=yes --enable-gold=yes
--enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-linker-build-id
--enable-lto --enable-plugins --enable-threads=posix
--with-pkgversion=Compiler-Explorer-Build

Thread model: posix

Supported LTO compression algorithms: zlib

gcc version 10.2.0 (Compiler-Explorer-Build) 

COLLECT_GCC_OPTIONS='-fdiagnostics-color=always' '-g' '-o' './output.s'
'-masm=intel' '-S' '-v' '-O3' '-g' '-Wall' '-Wextra' '-fno-strict-aliasing'
'-fwrapv' '-fno-aggressive-loop-optimizations' '-shared-libgcc'
'-mtune=generic' '-march=x86-64'


/opt/compiler-explorer/gcc-10.2.0/bin/../libexec/gcc/x86_64-linux-gnu/10.2.0/cc1plus
-quiet -v -imultiarch x86_64-linux-gnu -iprefix
/opt/compiler-explorer/gcc-10.2.0/bin/../lib/gcc/x86_64-linux-gnu/10.2.0/
-D_GNU_SOURCE <source> -quiet -dumpbase example.cpp -masm=intel -mtune=generic
-march=x86-64 -auxbase-strip ./output.s -g -g -O3 -Wall -Wextra -version
-fdiagnostics-color=always -fno-strict-aliasing -fwrapv
-fno-aggressive-loop-optimizations -o ./output.s

GNU C++14 (Compiler-Explorer-Build) version 10.2.0 (x86_64-linux-gnu)

        compiled by GNU C version 7.5.0, GMP version 6.1.0, MPFR version 3.1.4,
MPC version 1.0.3, isl version isl-0.18-GMP



GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072

[Bug c++/97255] [8/9/10/11 Regression] Vectorizer gives a boolean a value of 255

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97255

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2020-09-30
                 CC|                            |marxin at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org
     Ever confirmed|0                           |1
            Summary|Vectorizer gives a boolean  |[8/9/10/11 Regression]
                   |a value of 255              |Vectorizer gives a boolean
                   |                            |a value of 255
           Keywords|                            |wrong-code

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Confirmed, started with r7-717-geb09cdcb1a8b55b9.

[Bug tree-optimization/97255] [8/9/10/11 Regression] Vectorizer gives a boolean a value of 255

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97255

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |tree-optimization
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org
   Target Milestone|---                         |8.5
             Status|NEW                         |ASSIGNED

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
I will have a look.

[Bug tree-optimization/97255] [8/9/10/11 Regression] Vectorizer gives a boolean a value of 255

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97255

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
OK, so it's SRA that creates the IL that ultimatively confuses the vectorizer.
SRA transforms the bool accesses into unsigned char ones:

   _32 = in1s_31 != 0;
-  MEM <struct Array> [(bool &)&x].m_arr[1] = _32;
+  _7 = VIEW_CONVERT_EXPR<unsigned char>(_32);
+  x$1_16 = _7;
...
   _5 = out_17(D) + _2;
-  *_5 = x;
+  MEM <unsigned char> [(struct Array *)_5] = x_15;
+  MEM <unsigned char> [(struct Array *)_5 + 1B] = x$1_16;
+  MEM <unsigned char> [(struct Array *)_5 + 2B] = x$2_23;
+  MEM <unsigned char> [(struct Array *)_5 + 3B] = x$3_28;

we do not recognize the VIEW_CONVERT_EXPR as bool pattern.  I have a fix.

[Bug tree-optimization/97255] [8/9/10 Regression] Vectorizer gives a boolean a value of 255

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97255

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[8/9/10/11 Regression]      |[8/9/10 Regression]
                   |Vectorizer gives a boolean  |Vectorizer gives a boolean
                   |a value of 255              |a value of 255
      Known to work|                            |11.0
           Priority|P3                          |P2

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
commit 36e691d3a62145fda1f4a1b3143d215cc113c10a (origin/master, origin/HEAD)
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Oct 1 09:29:32 2020 +0200

    tree-optimization/97255 - missing vector bool pattern of SRAed bool

    SRA tends to use VIEW_CONVERT_EXPR when replacing bool fields with
    unsigned char fields.  Those are not handled in vector bool pattern
    detection causing vector true values to leak.  The following fixes
    this by turning those into b ? 1 : 0 as well.

    2020-10-01  Richard Biener  <rguenther@suse.de>

            * tree-vect-patterns.c (vect_recog_bool_pattern): Also handle
            VIEW_CONVERT_EXPR.

            * g++.dg/vect/pr97255.cc: New testcase.

[Bug tree-optimization/97255] [8/9/10 Regression] Vectorizer gives a boolean a value of 255

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97255

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:67baa11f68e72cf562c491a8107bcdf3f1d6fc9b

commit r10-8878-g67baa11f68e72cf562c491a8107bcdf3f1d6fc9b
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Oct 1 09:29:32 2020 +0200

    tree-optimization/97255 - missing vector bool pattern of SRAed bool

    SRA tends to use VIEW_CONVERT_EXPR when replacing bool fields with
    unsigned char fields.  Those are not handled in vector bool pattern
    detection causing vector true values to leak.  The following fixes
    this by turning those into b ? 1 : 0 as well.

    2020-10-01  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/97255
            * tree-vect-patterns.c (vect_recog_bool_pattern): Also handle
            VIEW_CONVERT_EXPR.

            * g++.dg/vect/pr97255.cc: New testcase.

[Bug tree-optimization/97255] [8/9 Regression] Vectorizer gives a boolean a value of 255

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97255

--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-9 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:f720a0d776252aac3002a0a9307a96465f1975bd

commit r9-9091-gf720a0d776252aac3002a0a9307a96465f1975bd
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Oct 1 09:29:32 2020 +0200

    tree-optimization/97255 - missing vector bool pattern of SRAed bool

    SRA tends to use VIEW_CONVERT_EXPR when replacing bool fields with
    unsigned char fields.  Those are not handled in vector bool pattern
    detection causing vector true values to leak.  The following fixes
    this by turning those into b ? 1 : 0 as well.

    2020-10-01  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/97255
            * tree-vect-patterns.c (vect_recog_bool_pattern): Also handle
            VIEW_CONVERT_EXPR.

            * g++.dg/vect/pr97255.cc: New testcase.

    (cherry picked from commit 36e691d3a62145fda1f4a1b3143d215cc113c10a)

[Bug tree-optimization/97255] [8 Regression] Vectorizer gives a boolean a value of 255

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97255

--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-8 branch has been updated by Richard Biener
<rguenth@gcc.gnu.org>:

https://gcc.gnu.org/g:87da0caaec663bd427147c04e5784d7843ede96a

commit r8-10806-g87da0caaec663bd427147c04e5784d7843ede96a
Author: Richard Biener <rguenther@suse.de>
Date:   Thu Oct 1 09:29:32 2020 +0200

    tree-optimization/97255 - missing vector bool pattern of SRAed bool

    SRA tends to use VIEW_CONVERT_EXPR when replacing bool fields with
    unsigned char fields.  Those are not handled in vector bool pattern
    detection causing vector true values to leak.  The following fixes
    this by turning those into b ? 1 : 0 as well.

    2020-10-01  Richard Biener  <rguenther@suse.de>

            PR tree-optimization/97255
            * tree-vect-patterns.c (vect_recog_bool_pattern): Also handle
            VIEW_CONVERT_EXPR.

            * g++.dg/vect/pr97255.cc: New testcase.

    (cherry picked from commit f720a0d776252aac3002a0a9307a96465f1975bd)

[Bug tree-optimization/97255] [8 Regression] Vectorizer gives a boolean a value of 255

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97255

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |8.4.0
             Status|ASSIGNED                    |RESOLVED
      Known to work|                            |8.4.1
         Resolution|---                         |FIXED

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed.