llvmpipe: implement dual source blending

link up the fs outputs and blend inputs, and make sure the second blend source
is correctly loaded and converted (which is quite complex).
There's a slight refactoring of the monster generate_unswizzled_blend()
function where it makes sense to factor out alpha conversion (which needs
to run twice for dual source blend).
This passes piglit arb_blend_func_extended tests.

v2: remove new but ultimately not used function...

Reviewed-by: Brian Paul <[email protected]>

5 files changed, 210 insertions, 93 deletions

diff --git a/src/gallium/drivers/llvmpipe/lp_bld_blend.h b/src/gallium/drivers/llvmpipe/lp_bld_blend.h
index 4bd28678215..249a3454159 100644
--- a/src/gallium/drivers/llvmpipe/lp_bld_blend.h
+++ b/src/gallium/drivers/llvmpipe/lp_bld_blend.h
@@ -62,6 +62,7 @@ lp_build_blend_aos(struct gallivm_state *gallivm,
                    LLVMValueRef src,
                    LLVMValueRef src_alpha,
                    LLVMValueRef src1,
+                   LLVMValueRef src1_alpha,
                    LLVMValueRef dst,
                    LLVMValueRef mask,
                    LLVMValueRef const_,
diff --git a/src/gallium/drivers/llvmpipe/lp_bld_blend_aos.c b/src/gallium/drivers/llvmpipe/lp_bld_blend_aos.c
index 8e9e7fe8719..c4d04a26873 100644
--- a/src/gallium/drivers/llvmpipe/lp_bld_blend_aos.c
+++ b/src/gallium/drivers/llvmpipe/lp_bld_blend_aos.c
@@ -70,6 +70,7 @@ struct lp_build_blend_aos_context
    LLVMValueRef src;
    LLVMValueRef src_alpha;
    LLVMValueRef src1;
+   LLVMValueRef src1_alpha;
    LLVMValueRef dst;
    LLVMValueRef const_;
    LLVMValueRef const_alpha;
@@ -94,6 +95,7 @@ lp_build_blend_factor_unswizzled(struct lp_build_blend_aos_context *bld,
                                  boolean alpha)
 {
    LLVMValueRef src_alpha = bld->src_alpha ? bld->src_alpha : bld->src;
+   LLVMValueRef src1_alpha = bld->src1_alpha ? bld->src1_alpha : bld->src1;
    LLVMValueRef const_alpha = bld->const_alpha ? bld->const_alpha : bld->const_;
 
    switch (factor) {
@@ -123,8 +125,9 @@ lp_build_blend_factor_unswizzled(struct lp_build_blend_aos_context *bld,
    case PIPE_BLENDFACTOR_CONST_ALPHA:
       return const_alpha;
    case PIPE_BLENDFACTOR_SRC1_COLOR:
-   case PIPE_BLENDFACTOR_SRC1_ALPHA:
       return bld->src1;
+   case PIPE_BLENDFACTOR_SRC1_ALPHA:
+      return src1_alpha;
    case PIPE_BLENDFACTOR_INV_SRC_COLOR:
       if(!bld->inv_src)
          bld->inv_src = lp_build_comp(&bld->base, bld->src);
@@ -147,8 +150,9 @@ lp_build_blend_factor_unswizzled(struct lp_build_blend_aos_context *bld,
          bld->inv_const_alpha = lp_build_comp(&bld->base, const_alpha);
       return bld->inv_const_alpha;
    case PIPE_BLENDFACTOR_INV_SRC1_COLOR:
-   case PIPE_BLENDFACTOR_INV_SRC1_ALPHA:
       return lp_build_comp(&bld->base, bld->src1);
+   case PIPE_BLENDFACTOR_INV_SRC1_ALPHA:
+      return lp_build_comp(&bld->base, src1_alpha);
    default:
       assert(0);
       return bld->base.zero;
@@ -265,10 +269,13 @@ lp_build_blend_factor(struct lp_build_blend_aos_context *bld,
  * @param type          data type of the pixel vector
  * @param rt            render target index
  * @param src           blend src
+ * @param src_alpha     blend src alpha (if not included in src)
  * @param src1          second blend src (for dual source blend)
+ * @param src1_alpha    second blend src alpha (if not included in src1)
  * @param dst           blend dst
  * @param mask          optional mask to apply to the blending result
  * @param const_        const blend color
+ * @param const_alpha   const blend color alpha (if not included in const_)
  * @param swizzle       swizzle values for RGBA
  *
  * @return the result of blending src and dst
@@ -282,6 +289,7 @@ lp_build_blend_aos(struct gallivm_state *gallivm,
                    LLVMValueRef src,
                    LLVMValueRef src_alpha,
                    LLVMValueRef src1,
+                   LLVMValueRef src1_alpha,
                    LLVMValueRef dst,
                    LLVMValueRef mask,
                    LLVMValueRef const_,
@@ -307,6 +315,7 @@ lp_build_blend_aos(struct gallivm_state *gallivm,
    bld.dst = dst;
    bld.const_ = const_;
    bld.src_alpha = src_alpha;
+   bld.src1_alpha = src1_alpha;
    bld.const_alpha = const_alpha;
 
    /* Find the alpha channel if not provided seperately */
diff --git a/src/gallium/drivers/llvmpipe/lp_screen.c b/src/gallium/drivers/llvmpipe/lp_screen.c
index f3bc5166338..b9c1567bd55 100644
--- a/src/gallium/drivers/llvmpipe/lp_screen.c
+++ b/src/gallium/drivers/llvmpipe/lp_screen.c
@@ -115,7 +115,7 @@ llvmpipe_get_param(struct pipe_screen *screen, enum pipe_cap param)
    case PIPE_CAP_SM3:
       return 1;
    case PIPE_CAP_MAX_DUAL_SOURCE_RENDER_TARGETS:
-      return 0;
+      return 1;
    case PIPE_CAP_MAX_STREAM_OUTPUT_BUFFERS:
       return PIPE_MAX_SO_BUFFERS;
    case PIPE_CAP_ANISOTROPIC_FILTER:
diff --git a/src/gallium/drivers/llvmpipe/lp_state_fs.c b/src/gallium/drivers/llvmpipe/lp_state_fs.c
index 2b31c14c218..44a9fcb2e19 100644
--- a/src/gallium/drivers/llvmpipe/lp_state_fs.c
+++ b/src/gallium/drivers/llvmpipe/lp_state_fs.c
@@ -66,6 +66,7 @@
 #include "util/u_dump.h"
 #include "util/u_string.h"
 #include "util/u_simple_list.h"
+#include "util/u_dual_blend.h"
 #include "os/os_time.h"
 #include "pipe/p_shader_tokens.h"
 #include "draw/draw_context.h"
@@ -247,6 +248,8 @@ generate_fs(struct gallivm_state *gallivm,
    boolean simple_shader = (shader->info.base.file_count[TGSI_FILE_SAMPLER] == 0 &&
                             shader->info.base.num_inputs < 3 &&
                             shader->info.base.num_instructions < 8);
+   const boolean dual_source_blend = key->blend.rt[0].blend_enable &&
+                                     util_blend_state_is_dual(&key->blend, 0);
    unsigned attrib;
    unsigned chan;
    unsigned cbuf;
@@ -302,6 +305,12 @@ generate_fs(struct gallivm_state *gallivm,
          color[cbuf][chan] = lp_build_alloca(gallivm, vec_type, "color");
       }
    }
+   if (dual_source_blend) {
+      assert(key->nr_cbufs <= 1);
+      for(chan = 0; chan < TGSI_NUM_CHANNELS; ++chan) {
+         color[1][chan] = lp_build_alloca(gallivm, vec_type, "color1");
+      }
+   }
 
    /* do triangle edge testing */
    if (partial_mask) {
@@ -414,8 +423,9 @@ generate_fs(struct gallivm_state *gallivm,
    /* Color write  */
    for (attrib = 0; attrib < shader->info.base.num_outputs; ++attrib)
    {
-      if (shader->info.base.output_semantic_name[attrib] == TGSI_SEMANTIC_COLOR &&
-          shader->info.base.output_semantic_index[attrib] < key->nr_cbufs)
+      unsigned cbuf = shader->info.base.output_semantic_index[attrib];
+      if ((shader->info.base.output_semantic_name[attrib] == TGSI_SEMANTIC_COLOR) &&
+           ((cbuf < key->nr_cbufs) || (cbuf == 1 && dual_source_blend)))
       {
          unsigned cbuf = shader->info.base.output_semantic_index[attrib];
          for(chan = 0; chan < TGSI_NUM_CHANNELS; ++chan) {
@@ -478,6 +488,8 @@ generate_fs_loop(struct gallivm_state *gallivm,
    boolean simple_shader = (shader->info.base.file_count[TGSI_FILE_SAMPLER] == 0 &&
                             shader->info.base.num_inputs < 3 &&
                             shader->info.base.num_instructions < 8);
+   const boolean dual_source_blend = key->blend.rt[0].blend_enable &&
+                                     util_blend_state_is_dual(&key->blend, 0);
    unsigned attrib;
    unsigned chan;
    unsigned cbuf;
@@ -551,7 +563,15 @@ generate_fs_loop(struct gallivm_state *gallivm,
                                                        num_loop, "color");
       }
    }
-
+   if (dual_source_blend) {
+      assert(key->nr_cbufs <= 1);
+      for(chan = 0; chan < TGSI_NUM_CHANNELS; ++chan) {
+         out_color[1][chan] = lp_build_array_alloca(gallivm,
+                                                    lp_build_vec_type(gallivm,
+                                                                      type),
+                                                    num_loop, "color1");
+      }
+   }
 
 
    /* 'mask' will control execution based on quad's pixel alive/killed state */
@@ -656,10 +676,10 @@ generate_fs_loop(struct gallivm_state *gallivm,
    /* Color write  */
    for (attrib = 0; attrib < shader->info.base.num_outputs; ++attrib)
    {
-      if (shader->info.base.output_semantic_name[attrib] == TGSI_SEMANTIC_COLOR &&
-          shader->info.base.output_semantic_index[attrib] < key->nr_cbufs)
+      unsigned cbuf = shader->info.base.output_semantic_index[attrib];
+      if ((shader->info.base.output_semantic_name[attrib] == TGSI_SEMANTIC_COLOR) &&
+           ((cbuf < key->nr_cbufs) || (cbuf == 1 && dual_source_blend)))
       {
-         unsigned cbuf = shader->info.base.output_semantic_index[attrib];
          for(chan = 0; chan < TGSI_NUM_CHANNELS; ++chan) {
             if(outputs[attrib][chan]) {
                /* XXX: just initialize outputs to point at colors[] and
@@ -1285,6 +1305,95 @@ convert_from_blend_type(struct gallivm_state *gallivm,
 
 
 /**
+ * Convert alpha to same blend type as src
+ */
+static void
+convert_alpha(struct gallivm_state *gallivm,
+              struct lp_type row_type,
+              struct lp_type alpha_type,
+              const unsigned block_size,
+              const unsigned block_height,
+              const unsigned src_count,
+              const unsigned dst_channels,
+              const bool pad_inline,
+              LLVMValueRef* src_alpha)
+{
+   LLVMBuilderRef builder = gallivm->builder;
+   unsigned i, j;
+   unsigned length = row_type.length;
+   row_type.length = alpha_type.length;
+
+   /* Twiddle the alpha to match pixels */
+   lp_bld_quad_twiddle(gallivm, alpha_type, src_alpha, 4, src_alpha);
+
+   for (i = 0; i < 4; ++i) {
+      lp_build_conv(gallivm, alpha_type, row_type, &src_alpha[i], 1, &src_alpha[i], 1);
+   }
+
+   alpha_type = row_type;
+   row_type.length = length;
+
+   /* If only one channel we can only need the single alpha value per pixel */
+   if (src_count == 1) {
+      assert(dst_channels == 1);
+
+      lp_build_concat_n(gallivm, alpha_type, src_alpha, 4, src_alpha, src_count);
+   } else {
+      /* If there are more srcs than rows then we need to split alpha up */
+      if (src_count > block_height) {
+         for (i = src_count; i > 0; --i) {
+            unsigned pixels = block_size / src_count;
+            unsigned idx = i - 1;
+
+            src_alpha[idx] = lp_build_extract_range(gallivm, src_alpha[(idx * pixels) / 4], (idx * pixels) % 4, pixels);
+         }
+      }
+
+      /* If there is a src for each pixel broadcast the alpha across whole row */
+      if (src_count == block_size) {
+         for (i = 0; i < src_count; ++i) {
+            src_alpha[i] = lp_build_broadcast(gallivm, lp_build_vec_type(gallivm, row_type), src_alpha[i]);
+         }
+      } else {
+         unsigned pixels = block_size / src_count;
+         unsigned channels = pad_inline ? TGSI_NUM_CHANNELS : dst_channels;
+         unsigned alpha_span = 1;
+         LLVMValueRef shuffles[LP_MAX_VECTOR_LENGTH];
+
+         /* Check if we need 2 src_alphas for our shuffles */
+         if (pixels > alpha_type.length) {
+            alpha_span = 2;
+         }
+
+         /* Broadcast alpha across all channels, e.g. a1a2 to a1a1a1a1a2a2a2a2 */
+         for (j = 0; j < row_type.length; ++j) {
+            if (j < pixels * channels) {
+               shuffles[j] = lp_build_const_int32(gallivm, j / channels);
+            } else {
+               shuffles[j] = LLVMGetUndef(LLVMInt32TypeInContext(gallivm->context));
+            }
+         }
+
+         for (i = 0; i < src_count; ++i) {
+            unsigned idx1 = i, idx2 = i;
+
+            if (alpha_span > 1){
+               idx1 *= alpha_span;
+               idx2 = idx1 + 1;
+            }
+
+            src_alpha[i] = LLVMBuildShuffleVector(builder,
+                                                  src_alpha[idx1],
+                                                  src_alpha[idx2],
+                                                  LLVMConstVector(shuffles, row_type.length),
+                                                  "");
+         }
+      }
+   }
+}
+
+
+/**
  * Generates the blend function for unswizzled colour buffers
  * Also generates the read & write from colour buffer
  */
@@ -1296,7 +1405,7 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
                           unsigned int num_fs,
                           struct lp_type fs_type,
                           LLVMValueRef* fs_mask,
-                          LLVMValueRef fs_out_color[TGSI_NUM_CHANNELS][4],
+                          LLVMValueRef fs_out_color[PIPE_MAX_COLOR_BUFS][TGSI_NUM_CHANNELS][4],
                           LLVMValueRef context_ptr,
                           LLVMValueRef color_ptr,
                           LLVMValueRef stride,
@@ -1311,9 +1420,12 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
 
    LLVMBuilderRef builder = gallivm->builder;
    LLVMValueRef fs_src[4][TGSI_NUM_CHANNELS];
+   LLVMValueRef fs_src1[4][TGSI_NUM_CHANNELS];
    LLVMValueRef src_alpha[4 * 4];
+   LLVMValueRef src1_alpha[4 * 4];
    LLVMValueRef src_mask[4 * 4];
    LLVMValueRef src[4 * 4];
+   LLVMValueRef src1[4 * 4];
    LLVMValueRef dst[4 * 4];
    LLVMValueRef blend_color;
    LLVMValueRef blend_alpha;
@@ -1323,14 +1435,13 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
    struct lp_build_mask_context mask_ctx;
    struct lp_type mask_type;
    struct lp_type blend_type;
-   struct lp_type alpha_type;
    struct lp_type row_type;
    struct lp_type dst_type;
 
    unsigned char swizzle[TGSI_NUM_CHANNELS];
    unsigned vector_width;
+   unsigned src_channels = TGSI_NUM_CHANNELS;
    unsigned dst_channels;
-   unsigned src_channels;
    unsigned dst_count;
    unsigned src_count;
    unsigned i, j;
@@ -1341,8 +1452,9 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
 
    bool pad_inline = is_arithmetic_format(out_format_desc);
    bool has_alpha = false;
+   const boolean dual_source_blend = variant->key.blend.rt[0].blend_enable &&
+                                     util_blend_state_is_dual(&variant->key.blend, 0);
 
-   src_channels = TGSI_NUM_CHANNELS;
    mask_type = lp_int32_vec4_type();
    mask_type.length = fs_type.length;
 
@@ -1422,17 +1534,20 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
     */
    for (i = 0; i < num_fs; ++i) {
       /* Always load alpha for use in blending */
-      LLVMValueRef alpha = LLVMBuildLoad(builder, fs_out_color[alpha_channel][i], "");
+      LLVMValueRef alpha = LLVMBuildLoad(builder, fs_out_color[rt][alpha_channel][i], "");
 
       /* Load each channel */
       for (j = 0; j < dst_channels; ++j) {
-         fs_src[i][j] = LLVMBuildLoad(builder, fs_out_color[swizzle[j]][i], "");
+         fs_src[i][j] = LLVMBuildLoad(builder, fs_out_color[rt][swizzle[j]][i], "");
       }
 
       /* If 3 channels then pad to include alpha for 4 element transpose */
+      /*
+       * XXX If we include that here maybe could actually use it instead of
+       * separate alpha for blending?
+       */
       if (dst_channels == 3 && !has_alpha) {
          fs_src[i][3] = alpha;
-         swizzle[3] = 3;
       }
 
       /* We split the row_mask and row_alpha as we want 128bit interleave */
@@ -1447,6 +1562,25 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
          src_alpha[i] = alpha;
       }
    }
+   if (dual_source_blend) {
+      /* same as above except different src/dst, skip masks and comments... */
+      for (i = 0; i < num_fs; ++i) {
+         LLVMValueRef alpha = LLVMBuildLoad(builder, fs_out_color[1][alpha_channel][i], "");
+
+         for (j = 0; j < dst_channels; ++j) {
+            fs_src1[i][j] = LLVMBuildLoad(builder, fs_out_color[1][swizzle[j]][i], "");
+         }
+         if (dst_channels == 3 && !has_alpha) {
+            fs_src1[i][3] = alpha;
+         }
+         if (fs_type.length == 8) {
+            src1_alpha[i*2 + 0] = lp_build_extract_range(gallivm, alpha, 0, src_channels);
+            src1_alpha[i*2 + 1] = lp_build_extract_range(gallivm, alpha, src_channels, src_channels);
+         } else {
+            src1_alpha[i] = alpha;
+         }
+      }
+   }
 
    if (util_format_is_pure_integer(out_format)) {
       /*
@@ -1467,11 +1601,14 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
       }
    }
 
-
    /*
     * Pixel twiddle from fragment shader order to memory order
     */
    src_count = generate_fs_twiddle(gallivm, fs_type, num_fs, dst_channels, fs_src, src, pad_inline);
+   if (dual_source_blend) {
+      generate_fs_twiddle(gallivm, fs_type, num_fs, dst_channels, fs_src1, src1, pad_inline);
+   }
+
    src_channels = dst_channels < 3 ? dst_channels : 4;
    if (src_count != num_fs * src_channels) {
       unsigned ds = src_count / (num_fs * src_channels);
@@ -1480,12 +1617,17 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
    }
 
    blend_type = row_type;
-   alpha_type = fs_type;
-   alpha_type.length = 4;
    mask_type.length = 4;
 
    /* Convert src to row_type */
-   src_count = lp_build_conv_auto(gallivm, fs_type, &row_type, src, src_count, src);
+   if (dual_source_blend) {
+      struct lp_type old_row_type = row_type;
+      lp_build_conv_auto(gallivm, fs_type, &row_type, src, src_count, src);
+      src_count = lp_build_conv_auto(gallivm, fs_type, &old_row_type, src1, src_count, src1);
+   }
+   else {
+      src_count = lp_build_conv_auto(gallivm, fs_type, &row_type, src, src_count, src);
+   }
 
    /* If the rows are not an SSE vector, combine them to become SSE size! */
    if ((row_type.width * row_type.length) % 128) {
@@ -1494,6 +1636,9 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
 
       dst_count = src_count / (vector_width / bits);
       combined = lp_build_concat_n(gallivm, row_type, src, src_count, src, dst_count);
+      if (dual_source_blend) {
+         lp_build_concat_n(gallivm, row_type, src1, src_count, src1, dst_count);
+      }
 
       row_type.length *= combined;
       src_count /= combined;
@@ -1569,75 +1714,17 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
     * Alpha conversion
     */
    if (!has_alpha) {
-      unsigned length = row_type.length;
-      row_type.length = alpha_type.length;
-
-      /* Twiddle the alpha to match pixels */
-      lp_bld_quad_twiddle(gallivm, alpha_type, src_alpha, 4, src_alpha);
-
-      for (i = 0; i < 4; ++i) {
-         lp_build_conv(gallivm, alpha_type, row_type, &src_alpha[i], 1, &src_alpha[i], 1);
-      }
-
-      alpha_type = row_type;
-      row_type.length = length;
-
-      /* If only one channel we can only need the single alpha value per pixel */
-      if (src_count == 1) {
-         assert(dst_channels == 1);
-
-         lp_build_concat_n(gallivm, alpha_type, src_alpha, 4, src_alpha, src_count);
-      } else {
-         /* If there are more srcs than rows then we need to split alpha up */
-         if (src_count > block_height) {
-            for (i = src_count; i > 0; --i) {
-               unsigned pixels = block_size / src_count;
-               unsigned idx = i - 1;
-
-               src_alpha[idx] = lp_build_extract_range(gallivm, src_alpha[(idx * pixels) / 4], (idx * pixels) % 4, pixels);
-            }
-         }
-
-         /* If there is a src for each pixel broadcast the alpha across whole row */
-         if (src_count == block_size) {
-            for (i = 0; i < src_count; ++i) {
-               src_alpha[i] = lp_build_broadcast(gallivm, lp_build_vec_type(gallivm, row_type), src_alpha[i]);
-            }
-         } else {
-            unsigned pixels = block_size / src_count;
-            unsigned channels = pad_inline ? TGSI_NUM_CHANNELS : dst_channels;
-            unsigned alpha_span = 1;
-            LLVMValueRef shuffles[LP_MAX_VECTOR_LENGTH];
-
-            /* Check if we need 2 src_alphas for our shuffles */
-            if (pixels > alpha_type.length) {
-               alpha_span = 2;
-            }
-
-            /* Broadcast alpha across all channels, e.g. a1a2 to a1a1a1a1a2a2a2a2 */
-            for (j = 0; j < row_type.length; ++j) {
-               if (j < pixels * channels) {
-                  shuffles[j] = lp_build_const_int32(gallivm, j / channels);
-               } else {
-                  shuffles[j] = LLVMGetUndef(LLVMInt32TypeInContext(gallivm->context));
-               }
-            }
-
-            for (i = 0; i < src_count; ++i) {
-               unsigned idx1 = i, idx2 = i;
-
-               if (alpha_span > 1){
-                  idx1 *= alpha_span;
-                  idx2 = idx1 + 1;
-               }
-
-               src_alpha[i] = LLVMBuildShuffleVector(builder,
-                                                     src_alpha[idx1],
-                                                     src_alpha[idx2],
-                                                     LLVMConstVector(shuffles, row_type.length),
-                                                     "");
-            }
-         }
+      struct lp_type alpha_type = fs_type;
+      alpha_type.length = 4;
+      convert_alpha(gallivm, row_type, alpha_type,
+                    block_size, block_height,
+                    src_count, dst_channels,
+                    pad_inline, src_alpha);
+      if (dual_source_blend) {
+         convert_alpha(gallivm, row_type, alpha_type,
+                       block_size, block_height,
+                       src_count, dst_channels,
+                       pad_inline, src1_alpha);
       }
    }
 
@@ -1693,7 +1780,8 @@ generate_unswizzled_blend(struct gallivm_state *gallivm,
                                   rt,
                                   src[i],
                                   has_alpha ? NULL : src_alpha[i],
-                                  NULL,
+                                  src1[i],
+                                  has_alpha ? NULL : src1_alpha[i],
                                   dst[i],
                                   partial_mask ? src_mask[i] : NULL,
                                   blend_color,
@@ -1788,6 +1876,8 @@ generate_fragment(struct llvmpipe_context *lp,
    unsigned cbuf;
    boolean cbuf0_write_all;
    boolean try_loop = TRUE;
+   const boolean dual_source_blend = key->blend.rt[0].blend_enable &&
+                                     util_blend_state_is_dual(&key->blend, 0);
 
    assert(lp_native_vector_width / 32 >= 4);
 
@@ -1951,10 +2041,17 @@ generate_fragment(struct llvmpipe_context *lp,
                      mask_input,
                      thread_data_ptr);
 
-         for (cbuf = 0; cbuf < key->nr_cbufs; cbuf++)
+         for (cbuf = 0; cbuf < key->nr_cbufs; cbuf++) {
             for (chan = 0; chan < TGSI_NUM_CHANNELS; ++chan)
                fs_out_color[cbuf][chan][i] =
                   out_color[cbuf * !cbuf0_write_all][chan];
+         }
+         if (dual_source_blend) {
+            /* only support one dual source blend target hence always use output 1 */
+            for (chan = 0; chan < TGSI_NUM_CHANNELS; ++chan)
+               fs_out_color[1][chan][i] =
+                  out_color[1][chan];
+         }
       }
    }
    else {
@@ -2024,6 +2121,15 @@ generate_fragment(struct llvmpipe_context *lp,
                fs_out_color[cbuf][chan][i] = ptr;
             }
          }
+         if (dual_source_blend) {
+            /* only support one dual source blend target hence always use output 1 */
+            for (chan = 0; chan < TGSI_NUM_CHANNELS; ++chan) {
+               ptr = LLVMBuildGEP(builder,
+                                  color_store[1][chan],
+                                  &indexi, 1, "");
+               fs_out_color[1][chan][i] = ptr;
+            }
+         }
       }
    }
 
@@ -2052,7 +2158,7 @@ generate_fragment(struct llvmpipe_context *lp,
                              "");
 
       generate_unswizzled_blend(gallivm, cbuf, variant, key->cbuf_format[cbuf],
-                                num_fs, fs_type, fs_mask, fs_out_color[cbuf],
+                                num_fs, fs_type, fs_mask, fs_out_color,
                                 context_ptr, color_ptr, stride, partial_mask, do_branch);
    }
 
diff --git a/src/gallium/drivers/llvmpipe/lp_test_blend.c b/src/gallium/drivers/llvmpipe/lp_test_blend.c
index 6faaedfb848..c3d2714cb5f 100644
--- a/src/gallium/drivers/llvmpipe/lp_test_blend.c
+++ b/src/gallium/drivers/llvmpipe/lp_test_blend.c
@@ -177,7 +177,8 @@ add_blend_test(struct gallivm_state *gallivm,
    dst = LLVMBuildLoad(builder, dst_ptr, "dst");
    con = LLVMBuildLoad(builder, const_ptr, "const");
 
-   res = lp_build_blend_aos(gallivm, blend, format, type, rt, src, NULL, src1, dst, NULL, con, NULL, swizzle, 4);
+   res = lp_build_blend_aos(gallivm, blend, format, type, rt, src, NULL,
+                            src1, NULL, dst, NULL, con, NULL, swizzle, 4);
 
    lp_build_name(res, "res");