[Mesa-dev] [PATCH] gallivm: use fallback code for mul_hi with llvm >= 7.0

[Dave Airlie]

Reviewed-by: Dave Airlie <airlied at redhat.com>

On Thu, 29 Aug 2019 at 05:37, <sroland at vmware.com> wrote:
>
> From: Roland Scheidegger <sroland at vmware.com>
>
> LLVM 7.0 ditched the pmulu intrinsics.
> This is only a trivial patch to use the fallback code instead.
> It'll likely produce atrocious code since the pattern doesn't match what
> llvm itself uses in its autoupgrade paths, hence the pattern won't be
> recognized.
>
> Should fix https://bugs.freedesktop.org/show_bug.cgi?id=111496
> ---
>  src/gallium/auxiliary/gallivm/lp_bld_arit.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/src/gallium/auxiliary/gallivm/lp_bld_arit.c b/src/gallium/auxiliary/gallivm/lp_bld_arit.c
> index c4931c0b230..f1866c6625f 100644
> --- a/src/gallium/auxiliary/gallivm/lp_bld_arit.c
> +++ b/src/gallium/auxiliary/gallivm/lp_bld_arit.c
> @@ -1169,8 +1169,13 @@ lp_build_mul_32_lohi_cpu(struct lp_build_context *bld,
>      * https://llvm.org/bugs/show_bug.cgi?id=30845
>      * So, whip up our own code, albeit only for length 4 and 8 (which
>      * should be good enough)...
> +    * FIXME: For llvm >= 7.0 we should match the autoupgrade pattern
> +    * (bitcast/and/mul/shuffle for unsigned, bitcast/shl/ashr/mul/shuffle
> +    * for signed), which the fallback code does not, without this llvm
> +    * will likely still produce atrocious code.
>      */
> -   if ((bld->type.length == 4 || bld->type.length == 8) &&
> +   if (HAVE_LLVM < 0x0700 &&
> +       (bld->type.length == 4 || bld->type.length == 8) &&
>         ((util_cpu_caps.has_sse2 && (bld->type.sign == 0)) ||
>          util_cpu_caps.has_sse4_1)) {
>        const char *intrinsic = NULL;
> --
> 2.17.1
>
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