[Mesa-dev] [PATCH] gallivm: fix [IU]MUL_HI regression harder

[Roland Scheidegger]

Reviewed-by: Roland Scheidegger <sroland at vmware.com>

I'm curious though, is for radeonsi zext not equivalent to interleaving
the low 32bits of each number with zeros (and hence doing the a
uninterleave doesn't give you back the low respectively high bits)?

Roland

Am 09.11.2016 um 12:46 schrieb Nicolai Hähnle:
> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
> 
> The fix in commit 88f791db75e9f065bac8134e0937e1b76600aa36 was insufficient
> for radeonsi because the vector case was not handled properly. It seems
> piglit only covers the scalar case, unfortunately.
> 
> Fixes GL45-CTS.shader_bitfield_operation.[iu]mulExtended.*
> ---
>  src/gallium/auxiliary/gallivm/lp_bld_arit.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/src/gallium/auxiliary/gallivm/lp_bld_arit.c b/src/gallium/auxiliary/gallivm/lp_bld_arit.c
> index 43ad238..5553cb1 100644
> --- a/src/gallium/auxiliary/gallivm/lp_bld_arit.c
> +++ b/src/gallium/auxiliary/gallivm/lp_bld_arit.c
> @@ -1230,42 +1230,46 @@ lp_build_mul_32_lohi_cpu(struct lp_build_context *bld,
>   * Emits generic code.
>   */
>  LLVMValueRef
>  lp_build_mul_32_lohi(struct lp_build_context *bld,
>                       LLVMValueRef a,
>                       LLVMValueRef b,
>                       LLVMValueRef *res_hi)
>  {
>     struct gallivm_state *gallivm = bld->gallivm;
>     LLVMBuilderRef builder = gallivm->builder;
> -   LLVMValueRef tmp;
> +   LLVMValueRef tmp, shift, res_lo;
>     struct lp_type type_tmp;
> -   LLVMTypeRef wide_type, cast_type;
> +   LLVMTypeRef wide_type, narrow_type;
>  
>     type_tmp = bld->type;
> +   narrow_type = lp_build_vec_type(gallivm, type_tmp);
>     type_tmp.width *= 2;
>     wide_type = lp_build_vec_type(gallivm, type_tmp);
> -   type_tmp = bld->type;
> -   type_tmp.length *= 2;
> -   cast_type = lp_build_vec_type(gallivm, type_tmp);
> +   shift = lp_build_const_vec(gallivm, type_tmp, 32);
>  
>     if (bld->type.sign) {
>        a = LLVMBuildSExt(builder, a, wide_type, "");
>        b = LLVMBuildSExt(builder, b, wide_type, "");
>     } else {
>        a = LLVMBuildZExt(builder, a, wide_type, "");
>        b = LLVMBuildZExt(builder, b, wide_type, "");
>     }
>     tmp = LLVMBuildMul(builder, a, b, "");
> -   tmp = LLVMBuildBitCast(builder, tmp, cast_type, "");
> -   *res_hi = lp_build_uninterleave1(gallivm, bld->type.length * 2, tmp, 1);
> -   return lp_build_uninterleave1(gallivm, bld->type.length * 2, tmp, 0);
> +
> +   res_lo = LLVMBuildTrunc(builder, tmp, narrow_type, "");
> +
> +   /* Since we truncate anyway, LShr and AShr are equivalent. */
> +   tmp = LLVMBuildLShr(builder, tmp, shift, "");
> +   *res_hi = LLVMBuildTrunc(builder, tmp, narrow_type, "");
> +
> +   return res_lo;
>  }
>  
>  
>  /* a * b + c */
>  LLVMValueRef
>  lp_build_mad(struct lp_build_context *bld,
>               LLVMValueRef a,
>               LLVMValueRef b,
>               LLVMValueRef c)
>  {
>