[Mesa-dev] [PATCH 3/5] draw/llvm: fix viewport transformations

[Roland Scheidegger]

Am 24.04.2013 00:58, schrieb Zack Rusin:
> This was a very serious bug. We were always doing the viewport
> transformations on the first output of the vertex shader. That means
> that every application that was storing position in anything but
> OUT[0] was outputing untransformed vertices and had broken output
> for whatever it was storing at OUT[0]. Correctly take into
> consideration where the vertex position is actually stored.
> 
> Signed-off-by: Zack Rusin <zackr at vmware.com>
> ---
>  src/gallium/auxiliary/draw/draw_llvm.c |    9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/src/gallium/auxiliary/draw/draw_llvm.c b/src/gallium/auxiliary/draw/draw_llvm.c
> index 594b0ec..bdd24be 100644
> --- a/src/gallium/auxiliary/draw/draw_llvm.c
> +++ b/src/gallium/auxiliary/draw/draw_llvm.c
> @@ -996,18 +996,19 @@ generate_viewport(struct draw_llvm_variant *variant,
>     int i;
>     struct gallivm_state *gallivm = variant->gallivm;
>     struct lp_type f32_type = vs_type;
> +   const unsigned pos = draw_current_shader_position_output(variant->llvm->draw);
>     LLVMTypeRef vs_type_llvm = lp_build_vec_type(gallivm, vs_type);
> -   LLVMValueRef out3 = LLVMBuildLoad(builder, outputs[0][3], ""); /*w0 w1 .. wn*/
> +   LLVMValueRef out3 = LLVMBuildLoad(builder, outputs[pos][3], ""); /*w0 w1 .. wn*/
>     LLVMValueRef const1 = lp_build_const_vec(gallivm, f32_type, 1.0);       /*1.0 1.0 1.0 1.0*/
>     LLVMValueRef vp_ptr = draw_jit_context_viewport(gallivm, context_ptr);
>  
>     /* for 1/w convention*/
>     out3 = LLVMBuildFDiv(builder, const1, out3, "");
> -   LLVMBuildStore(builder, out3, outputs[0][3]);
> +   LLVMBuildStore(builder, out3, outputs[pos][3]);
>  
>     /* Viewport Mapping */
>     for (i=0; i<3; i++) {
> -      LLVMValueRef out = LLVMBuildLoad(builder, outputs[0][i], ""); /*x0 x1 .. xn*/
> +      LLVMValueRef out = LLVMBuildLoad(builder, outputs[pos][i], ""); /*x0 x1 .. xn*/
>        LLVMValueRef scale;
>        LLVMValueRef trans;
>        LLVMValueRef scale_i;
> @@ -1033,7 +1034,7 @@ generate_viewport(struct draw_llvm_variant *variant,
>        out = LLVMBuildFAdd(builder, out, trans, "");
>  
>        /* store transformed outputs */
> -      LLVMBuildStore(builder, out, outputs[0][i]);
> +      LLVMBuildStore(builder, out, outputs[pos][i]);
>     }
>  
>  }
> 

The change itself looks good but I think there's quite some more
assumptions that position must be output zero elsewhere.

Roland