[Mesa-dev] [PATCH] llvmpipe: get rid of barycentric calculation of a0

[sroland at vmware.com]

From: Roland Scheidegger <sroland at vmware.com>

Didn't really work as well as hoped (in particular it was not generally
more accurate), will solve this differently.
---
 src/gallium/drivers/llvmpipe/lp_state_setup.c |   70 ++-----------------------
 1 file changed, 4 insertions(+), 66 deletions(-)

diff --git a/src/gallium/drivers/llvmpipe/lp_state_setup.c b/src/gallium/drivers/llvmpipe/lp_state_setup.c
index 9c17d76..1d79a4a 100644
--- a/src/gallium/drivers/llvmpipe/lp_state_setup.c
+++ b/src/gallium/drivers/llvmpipe/lp_state_setup.c
@@ -49,16 +49,6 @@
 #include "lp_state_fs.h"
 #include "lp_state_setup.h"
 
-/*
- * Set if the start point for interpolation should be calculated with a
- * more accurate method (barycentric interpolation).
- * Unfortunately, actual interpolation results of small tris with steep
- * gradients far away from the origin are still very busted, this does
- * nothing to change that (in fact it may make it worse), but some tests
- * (don't ask) really want accurate values at origin (and ONLY origin).
- */
-#define ACCURATE_A0 0
-
 
 /* currently organized to interpolate full float[4] attributes even
  * when some elements are unused.  Later, can pack vertex data more
@@ -86,9 +76,6 @@ struct lp_setup_args
    LLVMValueRef dy01_ooa;
    LLVMValueRef dx20_ooa;
    LLVMValueRef dx01_ooa;
-   LLVMValueRef e01o;
-   LLVMValueRef e20o;
-   LLVMValueRef e12o;
    struct lp_build_context bld;
 };
 
@@ -410,7 +397,6 @@ emit_coef4( struct gallivm_state *gallivm,
             LLVMValueRef a2)
 {
    LLVMBuilderRef b = gallivm->builder;
-   bool accurate_a0 = ACCURATE_A0;
    LLVMValueRef attr_0;
    LLVMValueRef dy20_ooa = args->dy20_ooa;
    LLVMValueRef dy01_ooa = args->dy01_ooa;
@@ -435,19 +421,10 @@ emit_coef4( struct gallivm_state *gallivm,
 
    /* Calculate a0 - the attribute value at the origin
     */
-   if (!accurate_a0) {
-      LLVMValueRef dadx_x0    = LLVMBuildFMul(b, dadx, x0_center, "dadx_x0");
-      LLVMValueRef dady_y0    = LLVMBuildFMul(b, dady, y0_center, "dady_y0");
-      LLVMValueRef attr_v0    = LLVMBuildFAdd(b, dadx_x0, dady_y0, "attr_v0");
-      attr_0                  = LLVMBuildFSub(b, a0, attr_v0, "attr_0");
-   }
-   else {
-      LLVMValueRef ao2 = LLVMBuildFMul(b, args->e01o, a2, "");
-      LLVMValueRef ao1 = LLVMBuildFMul(b, args->e20o, a1, "");
-      LLVMValueRef ao0 = LLVMBuildFMul(b, args->e12o, a0, "");
-      attr_0 = LLVMBuildFAdd(b, ao0, ao1, "");
-      attr_0 = LLVMBuildFAdd(b, attr_0, ao2, "");
-   }
+   LLVMValueRef dadx_x0    = LLVMBuildFMul(b, dadx, x0_center, "dadx_x0");
+   LLVMValueRef dady_y0    = LLVMBuildFMul(b, dady, y0_center, "dady_y0");
+   LLVMValueRef attr_v0    = LLVMBuildFAdd(b, dadx_x0, dady_y0, "attr_v0");
+   attr_0                  = LLVMBuildFSub(b, a0, attr_v0, "attr_0");
 
    store_coef(gallivm, args, slot, attr_0, dadx, dady);
 }
@@ -663,7 +640,6 @@ init_args(struct gallivm_state *gallivm,
    LLVMValueRef attr_pos[3];
    struct lp_type typef4 = lp_type_float_vec(32, 128);
    struct lp_build_context bld;
-   bool accurate_a0 = ACCURATE_A0;
 
    lp_build_context_init(&bld, gallivm, typef4);
    args->bld = bld;
@@ -708,44 +684,6 @@ init_args(struct gallivm_state *gallivm,
    dxy20 = LLVMBuildFMul(b, dxy20, ooa, "");
    dxy01 = LLVMBuildFMul(b, dxy01, ooa, "");
 
-   if (accurate_a0) {
-      LLVMValueRef xy1xy2, xy1xy2_center, dxy12, dyx01, dyx12yx20;
-      LLVMValueRef p0, p1p2, tmp0, tmp1, shuf0145, shuf1054, shuf1u3u;
-
-      shuffles[0] = zeroi;
-      shuffles[1] = onei;
-      shuffles[2] = lp_build_const_int32(gallivm, 4);
-      shuffles[3] = lp_build_const_int32(gallivm, 5);
-      shuf0145 = LLVMConstVector(shuffles, 4);
-      shuffles[0] = onei;
-      shuffles[1] = zeroi;
-      shuffles[2] = lp_build_const_int32(gallivm, 5);
-      shuffles[3] = lp_build_const_int32(gallivm, 4);
-      shuf1054 = LLVMConstVector(shuffles, 4);
-      shuffles[0] = onei;
-      shuffles[1] = LLVMGetUndef(shuf_type);
-      shuffles[2] = lp_build_const_int32(gallivm, 3);
-      shuffles[3] = LLVMGetUndef(shuf_type);
-      shuf1u3u = LLVMConstVector(shuffles, 4);
-
-      xy1xy2 = LLVMBuildShuffleVector(b, attr_pos[1], attr_pos[2], shuf0145, "");
-      xy1xy2_center = LLVMBuildFSub(b, xy1xy2, pixel_center, "");
-      dxy12 = LLVMBuildFSub(b, attr_pos[1], attr_pos[2], "dxy12");
-      dxy12 = LLVMBuildFMul(b, dxy12, ooa, "");
-      dyx12yx20 = LLVMBuildShuffleVector(b, dxy12, dxy20, shuf1054, "dyx12yx20");
-      dyx01 = LLVMBuildShuffleVector(b, dxy01, dxy01, shuf10, "");
-      p0 = LLVMBuildFMul(b, dyx01, xy0_center, "");
-      p1p2 = LLVMBuildFMul(b, dyx12yx20, xy1xy2_center, "");
-      tmp0 = LLVMBuildExtractElement(b, p0, zeroi, "");
-      tmp1 = LLVMBuildExtractElement(b, p0, onei, "");
-      args->e01o = lp_build_broadcast_scalar(&bld, LLVMBuildFSub(b, tmp0, tmp1, "e01o"));
-      tmp1 = LLVMBuildShuffleVector(b, p1p2, p1p2, shuf1u3u, "");
-      tmp0 = LLVMBuildFSub(b, p1p2, tmp1, "e12o20o");
-      args->e12o = lp_build_extract_broadcast(gallivm, typef4, typef4, tmp0, zeroi);
-      args->e20o = lp_build_extract_broadcast(gallivm, typef4, typef4, tmp0,
-                                              lp_build_const_int32(gallivm, 2));
-   }
-
    args->dy20_ooa  = lp_build_extract_broadcast(gallivm, typef4, typef4, dxy20, onei);
    args->dy01_ooa  = lp_build_extract_broadcast(gallivm, typef4, typef4, dxy01, onei);
 
-- 
1.7.9.5