Re: [PATCH] tcg/optimize: Fix TCG_COND_TST* simplification of setcond2

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> Fix a typo in the argument movement.
>
> Cc: qemu-stable@nongnu.org
> Fixes: ceb9ee06b71 ("tcg/optimize: Handle TCG_COND_TST{EQ,NE}")
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2413
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  tcg/optimize.c               |  2 +-
>  tests/tcg/x86_64/test-2413.c | 30 ++++++++++++++++++++++++++++++
>  2 files changed, 31 insertions(+), 1 deletion(-)
>  create mode 100644 tests/tcg/x86_64/test-2413.c
>
> diff --git a/tcg/optimize.c b/tcg/optimize.c
> index 8886f7037a..ba16ec27e2 100644
> --- a/tcg/optimize.c
> +++ b/tcg/optimize.c
> @@ -2384,7 +2384,7 @@ static bool fold_setcond2(OptContext *ctx, TCGOp *op)
>  
>      case TCG_COND_TSTEQ:
>      case TCG_COND_TSTNE:
> -        if (arg_is_const_val(op->args[2], 0)) {
> +        if (arg_is_const_val(op->args[3], 0)) {
>              goto do_setcond_high;
>          }
>          if (arg_is_const_val(op->args[4], 0)) {
> diff --git a/tests/tcg/x86_64/test-2413.c b/tests/tcg/x86_64/test-2413.c
> new file mode 100644
> index 0000000000..a0e4d25093
> --- /dev/null
> +++ b/tests/tcg/x86_64/test-2413.c
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/* Copyright 2024 Linaro, Ltd. */
> +/* See https://gitlab.com/qemu-project/qemu/-/issues/2413 */
> +
> +#include <assert.h>

This also needs:

X86_64_TESTS += test-2413

in the Makefile.

> +
> +void test(unsigned long *a, unsigned long *d, unsigned long c)
> +{
> +    asm("xorl %%eax, %%eax\n\t"
> +        "xorl %%edx, %%edx\n\t"
> +        "testb $0x20, %%cl\n\t"
> +        "sete %%al\n\t"
> +        "setne %%dl\n\t"
> +        "shll %%cl, %%eax\n\t"
> +        "shll %%cl, %%edx\n\t"
> +        : "=a"(*a), "=d"(*d)
> +        : "c"(c));
> +}
> +
> +int main(void)
> +{
> +    long a, c, d;
> +
> +    for (c = 0; c < 64; c++) {
> +        test(&a, &d, c);
> +        assert(a == (c & 0x20 ? 0 : 1u << (c & 0x1f)));
> +        assert(d == (c & 0x20 ? 1u << (c & 0x1f) : 0));
> +    }
> +    return 0;
> +}

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro