draw: fix splitting of line loops (v2)

When the draw module splits long line loops, the sections are emitted
as line strips.  But the primitive type wasn't set correctly so each
section was being drawn as a loop, introducing extra line segments.

To fix this, we pass a new DRAW_LINE_LOOP_AS_STRIP flag to the run()
function.  The linear/elt_run() functions have to check for this flag
and set their primitive type accordingly.

No piglit regressions.  Fixes piglit's lineloop with -count 4097 or
higher.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=81174

Reviewed-by: Roland Scheidegger <[email protected]>

4 files changed, 32 insertions, 8 deletions

diff --git a/src/gallium/auxiliary/draw/draw_private.h b/src/gallium/auxiliary/draw/draw_private.h
index 0ad94bb031f..5584c4a222c 100644
--- a/src/gallium/auxiliary/draw/draw_private.h
+++ b/src/gallium/auxiliary/draw/draw_private.h
@@ -355,8 +355,9 @@ struct draw_vertex_info {
 };
 
 /* these flags are set if the primitive is a segment of a larger one */
-#define DRAW_SPLIT_BEFORE 0x1
-#define DRAW_SPLIT_AFTER  0x2
+#define DRAW_SPLIT_BEFORE        0x1
+#define DRAW_SPLIT_AFTER         0x2
+#define DRAW_LINE_LOOP_AS_STRIP  0x4
 
 struct draw_prim_info {
    boolean linear;
diff --git a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c
index ffec863ae6f..aa20b918f50 100644
--- a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c
+++ b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline.c
@@ -359,6 +359,16 @@ fetch_pipeline_generic(struct draw_pt_middle_end *middle,
 }
 
 
+static inline unsigned
+prim_type(unsigned prim, unsigned flags)
+{
+   if (flags & DRAW_LINE_LOOP_AS_STRIP)
+      return PIPE_PRIM_LINE_STRIP;
+   else
+      return prim;
+}
+
+
 static void
 fetch_pipeline_run(struct draw_pt_middle_end *middle,
                    const unsigned *fetch_elts,
@@ -380,7 +390,7 @@ fetch_pipeline_run(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = draw_count;
    prim_info.elts = draw_elts;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &draw_count;
@@ -408,7 +418,7 @@ fetch_pipeline_linear_run(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = count;
    prim_info.elts = NULL;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &count;
@@ -439,7 +449,7 @@ fetch_pipeline_linear_run_elts(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = draw_count;
    prim_info.elts = draw_elts;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &draw_count;
diff --git a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c
index e42c4af0e70..2d7569b0fdf 100644
--- a/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c
+++ b/src/gallium/auxiliary/draw/draw_pt_fetch_shade_pipeline_llvm.c
@@ -473,6 +473,16 @@ llvm_pipeline_generic(struct draw_pt_middle_end *middle,
 }
 
 
+static inline unsigned
+prim_type(unsigned prim, unsigned flags)
+{
+   if (flags & DRAW_LINE_LOOP_AS_STRIP)
+      return PIPE_PRIM_LINE_STRIP;
+   else
+      return prim;
+}
+
+
 static void
 llvm_middle_end_run(struct draw_pt_middle_end *middle,
                     const unsigned *fetch_elts,
@@ -494,7 +504,7 @@ llvm_middle_end_run(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = draw_count;
    prim_info.elts = draw_elts;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &draw_count;
@@ -522,7 +532,7 @@ llvm_middle_end_linear_run(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = count;
    prim_info.elts = NULL;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &count;
@@ -552,7 +562,7 @@ llvm_middle_end_linear_run_elts(struct draw_pt_middle_end *middle,
    prim_info.start = 0;
    prim_info.count = draw_count;
    prim_info.elts = draw_elts;
-   prim_info.prim = fpme->input_prim;
+   prim_info.prim = prim_type(fpme->input_prim, prim_flags);
    prim_info.flags = prim_flags;
    prim_info.primitive_count = 1;
    prim_info.primitive_lengths = &draw_count;
diff --git a/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h b/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h
index 0afabb01398..6da79b9490b 100644
--- a/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h
+++ b/src/gallium/auxiliary/draw/draw_pt_vsplit_tmp.h
@@ -249,6 +249,9 @@ vsplit_segment_loop_linear(struct vsplit_frontend *vsplit, unsigned flags,
 
    assert(icount + !!close_loop <= vsplit->segment_size);
 
+   /* need to draw the sections of the line loop as line strips */
+   flags |= DRAW_LINE_LOOP_AS_STRIP;
+
    if (close_loop) {
       for (nr = 0; nr < icount; nr++)
          vsplit->fetch_elts[nr] = istart + nr;