[Mesa-dev] [PATCH 2/2] llvmpipe: Improve color buffer loads/stores alignment.

[Roland Scheidegger]

Am 30.11.2012 18:43, schrieb jfonseca at vmware.com:
> From: José Fonseca <jfonseca at vmware.com>
> 
> Tell LLVM the exact alignment we can guarantee, based on the fs block
> dimensions, pixel format, and the alignment of the resource base pointer
> and stride.
> ---
>  src/gallium/drivers/llvmpipe/lp_state_fs.c |   31 +++++++++++++++++++---------
>  1 file changed, 21 insertions(+), 10 deletions(-)
> 
> diff --git a/src/gallium/drivers/llvmpipe/lp_state_fs.c b/src/gallium/drivers/llvmpipe/lp_state_fs.c
> index 2d2e346..6819d33 100644
> --- a/src/gallium/drivers/llvmpipe/lp_state_fs.c
> +++ b/src/gallium/drivers/llvmpipe/lp_state_fs.c
> @@ -839,7 +839,8 @@ load_unswizzled_block(struct gallivm_state *gallivm,
>                        unsigned block_height,
>                        LLVMValueRef* dst,
>                        struct lp_type dst_type,
> -                      unsigned dst_count)
> +                      unsigned dst_count,
> +                      unsigned dst_alignment)
>  {
>     LLVMBuilderRef builder = gallivm->builder;
>     unsigned row_size = dst_count / block_height;
> @@ -866,9 +867,7 @@ load_unswizzled_block(struct gallivm_state *gallivm,
>  
>        dst[i] = LLVMBuildLoad(builder, dst_ptr, "");
>  
> -      if ((dst_type.length % 3) == 0) {
> -         lp_set_load_alignment(dst[i], dst_type.width / 8);
> -      }
> +      lp_set_load_alignment(dst[i], dst_alignment);
>     }
>  }
>  
> @@ -884,7 +883,8 @@ store_unswizzled_block(struct gallivm_state *gallivm,
>                         unsigned block_height,
>                         LLVMValueRef* src,
>                         struct lp_type src_type,
> -                       unsigned src_count)
> +                       unsigned src_count,
> +                       unsigned src_alignment)
>  {
>     LLVMBuilderRef builder = gallivm->builder;
>     unsigned row_size = src_count / block_height;
> @@ -893,6 +893,8 @@ store_unswizzled_block(struct gallivm_state *gallivm,
>     /* Ensure src exactly fits into block */
>     assert((block_width * block_height) % src_count == 0);
>  
> +
> +
extra whitespace.

>     for (i = 0; i < src_count; ++i) {
>        unsigned x = i % row_size;
>        unsigned y = i / row_size;
> @@ -911,9 +913,7 @@ store_unswizzled_block(struct gallivm_state *gallivm,
>  
>        src_ptr = LLVMBuildStore(builder, src[i], src_ptr);
>  
> -      if ((src_type.length % 3) == 0) {
> -         lp_set_store_alignment(src_ptr, src_type.width / 8);
> -      }
> +      lp_set_store_alignment(src_ptr, src_alignment);
>     }
>  }
>  
> @@ -1333,6 +1333,8 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
>  
>     const struct util_format_description* out_format_desc = util_format_description(out_format);
>  
> +   unsigned dst_alignment;
> +
>     bool pad_inline = is_arithmetic_format(out_format_desc);
>     bool has_alpha = false;
>  
> @@ -1340,6 +1342,13 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
>     mask_type = lp_int32_vec4_type();
>     mask_type.length = fs_type.length;
>  
> +   /* Compute the alignment of the destination pointer in bytes */
> +   dst_alignment = (block_width * out_format_desc->block.bits + 7)/(out_format_desc->block.width * 8);
> +   /* Force power-of-two alignment by extracting only the least-significant-bit */
> +   dst_alignment = 1 << (ffs(dst_alignment) - 1);
> +   /* Resource base and stride pointers are aligned to 16 bytes, so that's the maximum alignment we can guarantee */
> +   dst_alignment = MIN2(dst_alignment, 16);
I wonder if this is all necessary. block_width is a constant and pot,
and the formats are all pot-sized too, so trying to align this to pot
won't really do much.
So unless this somehow should handle non-pot block_width (and I don't
think this makes sense) this should probably be simplified.

> +
>     /* Do not bother executing code when mask is empty.. */
>     if (do_branch) {
>        check_mask = LLVMConstNull(lp_build_int_vec_type(gallivm, mask_type));
> @@ -1616,7 +1625,8 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
>  
>     dst_type.length *= 16 / dst_count;
>  
> -   load_unswizzled_block(gallivm, color_ptr, stride, block_width, block_height, dst, dst_type, dst_count);
> +   load_unswizzled_block(gallivm, color_ptr, stride, block_width, block_height,
> +                         dst, dst_type, dst_count, dst_alignment);
>  
>  
>     /*
> @@ -1681,7 +1691,8 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
>     /*
>      * Store blend result to memory
>      */
> -   store_unswizzled_block(gallivm, color_ptr, stride, block_width, block_height, dst, dst_type, dst_count);
> +   store_unswizzled_block(gallivm, color_ptr, stride, block_width, block_height,
> +                          dst, dst_type, dst_count, dst_alignment);
>  
>     if (do_branch) {
>        lp_build_mask_end(&mask_ctx);
> 

Otherwise, this (and rest of series) looks good to me.

Roland