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From: "zsojka at seznam dot cz" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/103302] New: wrong code with -fharden-compares
Date: Wed, 17 Nov 2021 14:13:13 +0000
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X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: wrong-code
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103302

            Bug ID: 103302
           Summary: wrong code with -fharden-compares
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: riscv64-unknown-linux-gnu

Created attachment 51824
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D51824&action=3Dedit
reduced testcase

Output:
$ riscv64-unknown-linux-gnu-gcc -Og -fharden-compares -fno-tree-dce
-fno-tree-fre testcase.c -static
$ qemu-riscv64 -- ./a.out=20
Trace/breakpoint trap

Debugging shows one of the compares on the first statement probably goes wr=
ong:

(gdb)=20
0x00000000000106ea      19        u32_0 <=3D (v512u128) (v512u128_0 !=3D u8=
_0);
(gdb)=20
0x0000000000010a48      24      }

I could find any other target where this testcase is failing.

$ riscv64-unknown-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=3D/repo/gcc-trunk/binary-latest-riscv64/bin/riscv64-unknown-lin=
ux-gnu-gcc
COLLECT_LTO_WRAPPER=3D/repo/gcc-trunk/binary-trunk-r12-5221-20211113015125-=
g2f3d43a3515-checking-yes-rtl-df-extra-riscv64/bin/../libexec/gcc/riscv64-u=
nknown-linux-gnu/12.0.0/lto-wrapper
Target: riscv64-unknown-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=3Dc,c++
--enable-valgrind-annotations --disable-nls --enable-checking=3Dyes,rtl,df,=
extra
--with-cloog --with-ppl --with-isl
--with-sysroot=3D/usr/riscv64-unknown-linux-gnu --build=3Dx86_64-pc-linux-g=
nu
--host=3Dx86_64-pc-linux-gnu --target=3Driscv64-unknown-linux-gnu
--with-ld=3D/usr/bin/riscv64-unknown-linux-gnu-ld
--with-as=3D/usr/bin/riscv64-unknown-linux-gnu-as --disable-multilib
--disable-libstdcxx-pch
--prefix=3D/repo/gcc-trunk//binary-trunk-r12-5221-20211113015125-g2f3d43a35=
15-checking-yes-rtl-df-extra-riscv64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.0.0 20211113 (experimental) (GCC)=