[Bug target/113209] New: [14] RISC-V rv64gcv_zvl256b vector: Runtime mismatch with rv64gc

[Bug target/113209] New: [14] RISC-V rv64gcv_zvl256b vector: Runtime mismatch with rv64gc

[patrick at rivosinc dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113209

            Bug ID: 113209
           Summary: [14] RISC-V rv64gcv_zvl256b vector: Runtime mismatch
                    with rv64gc
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: patrick at rivosinc dot com
  Target Milestone: ---

Testcase:
int b, c, d, f, i, a;
int e[1] = {0};
int *g = e;
int *k = e;
int *z;
long h;
int j[5] = {0,0,0,0,0};
void n() {
  if (c) {
    int **l = &z;
    *l = e;
    while (d)
      ;
  }
}
void o() {
  for (; b < 5; b += a) {
    n();
    for (h = 0; h < 5; h++)
      j[h] = 1;
    int m = *e != *g;
    a |= i <= m;
    f = -12;
    for (; f; f++)
      if (*k)
        break;
  }
}
int main() {
  o();
  if (a == 1)
    return 0;
  else
    return 1;
}

Commands:
> /scratch/tc-testing/tc-jan-1-trunk/build-rv64gcv/bin/riscv64-unknown-linux-gnu-gcc -march=rv64gcv_zvl256b -O3 red.c -o user-config.out
> QEMU_CPU=rv64,vlen=256,v=true,vext_spec=v1.0,Zve32f=true,Zve64f=true timeout --verbose -k 0.1 1 /scratch/tc-testing/tc-dec-22-trunk/build-rv64gcv/bin/qemu-riscv64 user-config.out
> echo $?
1

> /scratch/tc-testing/tc-jan-1-trunk/build-rv64gcv/bin/riscv64-unknown-linux-gnu-gcc -march=rv64gc -O3 red.c -o user-config.out
> QEMU_CPU=rv64,vlen=256,v=true,vext_spec=v1.0,Zve32f=true,Zve64f=true timeout --verbose -k 0.1 1 /scratch/tc-testing/tc-dec-22-trunk/build-rv64gcv/bin/qemu-riscv64 user-config.out
> echo $?
0

With a printf:
gcv_zvl256b
a = 9

gc
a = 1

Analysis:
Working backwards from a
a |= i <= m
Since true/false only evaluate to 1/0, 'a' should never be 9

[Bug target/113209] [14] RISC-V rv64gcv_zvl256b vector: Runtime mismatch with rv64gc

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113209

--- Comment #1 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Pan Li <panli@gcc.gnu.org>:

https://gcc.gnu.org/g:4a0a8dc1b88408222b88e10278017189f6144602

commit r14-6902-g4a0a8dc1b88408222b88e10278017189f6144602
Author: Juzhe-Zhong <juzhe.zhong@rivai.ai>
Date:   Thu Jan 4 06:38:43 2024 +0800

    RISC-V: Fix bug of earliest fusion for infinite loop[VSETVL PASS]

    As PR113206 and PR113209, the bugs happens on the following situation:

            li      a4,32
            ...
            vsetvli zero,a4,e8,m8,ta,ma
            ...
            slliw   a4,a3,24
            sraiw   a4,a4,24
            bge     a3,a1,.L8
            sb      a4,%lo(e)(a0)
            vsetvli zero,a4,e8,m8,ta,ma  --> a4 is polluted value not the
expected "32".
            ...
    .L7:
            j       .L7 ---> infinite loop.

    The root cause is that infinite loop confuse earliest computation and let
earliest fusion
    happens on unexpected place.

    Disable blocks that belong to infinite loop to fix this bug since applying
ealiest LCM fusion
    on infinite loop seems quite complicated and we don't see any benefits.

    Note that disabling earliest fusion on infinite loops doesn't hurt the
vsetvli performance,
    instead, it does improve codegen of some cases.

    Tested on both RV32 and RV64 no regression.

            PR target/113206
            PR target/113209

    gcc/ChangeLog:

            * config/riscv/riscv-vsetvl.cc (invalid_opt_bb_p): New function.
            (pre_vsetvl::compute_lcm_local_properties): Disable earliest fusion
on
            blocks belong to infinite loop.
            (pre_vsetvl::emit_vsetvl): Remove fake edges.
            * config/riscv/t-riscv: Add a new include file.

    gcc/testsuite/ChangeLog:

            * gcc.target/riscv/rvv/vsetvl/avl_single-23.c: Adapt test.
            * gcc.target/riscv/rvv/vsetvl/vlmax_call-1.c: Robostify test.
            * gcc.target/riscv/rvv/vsetvl/vlmax_call-2.c: Ditto.
            * gcc.target/riscv/rvv/vsetvl/vlmax_call-3.c: Ditto.
            * gcc.target/riscv/rvv/vsetvl/vlmax_conflict-5.c: Ditto.
            * gcc.target/riscv/rvv/vsetvl/vlmax_single_vtype-1.c: Ditto.
            * gcc.target/riscv/rvv/vsetvl/vlmax_single_vtype-2.c: Ditto.
            * gcc.target/riscv/rvv/vsetvl/vlmax_single_vtype-3.c: Ditto.
            * gcc.target/riscv/rvv/vsetvl/vlmax_single_vtype-4.c: Ditto.
            * gcc.target/riscv/rvv/vsetvl/vlmax_single_vtype-5.c: Ditto.
            * gcc.target/riscv/rvv/autovec/pr113206-1.c: New test.
            * gcc.target/riscv/rvv/autovec/pr113206-2.c: New test.
            * gcc.target/riscv/rvv/autovec/pr113209.c: New test.

[Bug target/113209] [14] RISC-V rv64gcv_zvl256b vector: Runtime mismatch with rv64gc

[patrick at rivosinc dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113209

Patrick O'Neill <patrick at rivosinc dot com> changed:

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

--- Comment #2 from Patrick O'Neill <patrick at rivosinc dot com> ---
Confirmed resolved.