llvmpipe: Fast path for sampling rgba8 textures with linear filtering.

Implement Keith's suggestion of doing most of the sampling with 16x8
and 8x16 AoS, and only doing the conversion to floating point SoA at
the very last step.

Improves gloss performance by 10%.

1 files changed, 256 insertions, 12 deletions

diff --git a/src/gallium/drivers/llvmpipe/lp_bld_sample_soa.c b/src/gallium/drivers/llvmpipe/lp_bld_sample_soa.c
index a7d2118c9b..f7a030fb8c 100644
--- a/src/gallium/drivers/llvmpipe/lp_bld_sample_soa.c
+++ b/src/gallium/drivers/llvmpipe/lp_bld_sample_soa.c
@@ -38,12 +38,15 @@
 #include "util/u_memory.h"
 #include "util/u_math.h"
 #include "util/u_format.h"
+#include "util/u_cpu_detect.h"
 #include "lp_bld_debug.h"
 #include "lp_bld_type.h"
 #include "lp_bld_const.h"
+#include "lp_bld_conv.h"
 #include "lp_bld_arit.h"
 #include "lp_bld_logic.h"
 #include "lp_bld_swizzle.h"
+#include "lp_bld_pack.h"
 #include "lp_bld_format.h"
 #include "lp_bld_sample.h"
 
@@ -76,12 +79,12 @@ struct lp_build_sample_context
 
 
 static void
-lp_build_sample_texel(struct lp_build_sample_context *bld,
-                      LLVMValueRef x,
-                      LLVMValueRef y,
-                      LLVMValueRef y_stride,
-                      LLVMValueRef data_ptr,
-                      LLVMValueRef *texel)
+lp_build_sample_texel_soa(struct lp_build_sample_context *bld,
+                          LLVMValueRef x,
+                          LLVMValueRef y,
+                          LLVMValueRef y_stride,
+                          LLVMValueRef data_ptr,
+                          LLVMValueRef *texel)
 {
    LLVMValueRef offset;
    LLVMValueRef packed;
@@ -109,6 +112,32 @@ lp_build_sample_texel(struct lp_build_sample_context *bld,
 
 
 static LLVMValueRef
+lp_build_sample_packed(struct lp_build_sample_context *bld,
+                       LLVMValueRef x,
+                       LLVMValueRef y,
+                       LLVMValueRef y_stride,
+                       LLVMValueRef data_ptr)
+{
+   LLVMValueRef offset;
+
+   offset = lp_build_sample_offset(&bld->int_coord_bld,
+                                   bld->format_desc,
+                                   x, y, y_stride,
+                                   data_ptr);
+
+   assert(bld->format_desc->block.width == 1);
+   assert(bld->format_desc->block.height == 1);
+   assert(bld->format_desc->block.bits <= bld->texel_type.width);
+
+   return lp_build_gather(bld->builder,
+                          bld->texel_type.length,
+                          bld->format_desc->block.bits,
+                          bld->texel_type.width,
+                          data_ptr, offset);
+}
+
+
+static LLVMValueRef
 lp_build_sample_wrap(struct lp_build_sample_context *bld,
                      LLVMValueRef coord,
                      LLVMValueRef length,
@@ -174,7 +203,7 @@ lp_build_sample_2d_nearest_soa(struct lp_build_sample_context *bld,
    x = lp_build_sample_wrap(bld, x, width,  bld->static_state->pot_width,  bld->static_state->wrap_s);
    y = lp_build_sample_wrap(bld, y, height, bld->static_state->pot_height, bld->static_state->wrap_t);
 
-   lp_build_sample_texel(bld, x, y, stride, data_ptr, texel);
+   lp_build_sample_texel_soa(bld, x, y, stride, data_ptr, texel);
 }
 
 
@@ -220,10 +249,10 @@ lp_build_sample_2d_linear_soa(struct lp_build_sample_context *bld,
    x1 = lp_build_sample_wrap(bld, x1, width,  bld->static_state->pot_width,  bld->static_state->wrap_s);
    y1 = lp_build_sample_wrap(bld, y1, height, bld->static_state->pot_height, bld->static_state->wrap_t);
 
-   lp_build_sample_texel(bld, x0, y0, stride, data_ptr, neighbors[0][0]);
-   lp_build_sample_texel(bld, x1, y0, stride, data_ptr, neighbors[0][1]);
-   lp_build_sample_texel(bld, x0, y1, stride, data_ptr, neighbors[1][0]);
-   lp_build_sample_texel(bld, x1, y1, stride, data_ptr, neighbors[1][1]);
+   lp_build_sample_texel_soa(bld, x0, y0, stride, data_ptr, neighbors[0][0]);
+   lp_build_sample_texel_soa(bld, x1, y0, stride, data_ptr, neighbors[0][1]);
+   lp_build_sample_texel_soa(bld, x0, y1, stride, data_ptr, neighbors[1][0]);
+   lp_build_sample_texel_soa(bld, x1, y1, stride, data_ptr, neighbors[1][1]);
 
    /* TODO: Don't interpolate missing channels */
    for(chan = 0; chan < 4; ++chan) {
@@ -238,6 +267,218 @@ lp_build_sample_2d_linear_soa(struct lp_build_sample_context *bld,
 
 
 static void
+lp_build_rgba8_to_f32_soa(LLVMBuilderRef builder,
+                          struct lp_type dst_type,
+                          LLVMValueRef packed,
+                          LLVMValueRef *rgba)
+{
+   LLVMValueRef mask = lp_build_int_const_scalar(dst_type, 0xff);
+   unsigned chan;
+
+   /* Decode the input vector components */
+   for (chan = 0; chan < 4; ++chan) {
+      unsigned start = chan*8;
+      unsigned stop = start + 8;
+      LLVMValueRef input;
+
+      input = packed;
+
+      if(start)
+         input = LLVMBuildLShr(builder, input, lp_build_int_const_scalar(dst_type, start), "");
+
+      if(stop < 32)
+         input = LLVMBuildAnd(builder, input, mask, "");
+
+      input = lp_build_unsigned_norm_to_float(builder, 8, dst_type, input);
+
+      rgba[chan] = input;
+   }
+}
+
+
+static void
+lp_build_sample_2d_linear_aos(struct lp_build_sample_context *bld,
+                              LLVMValueRef s,
+                              LLVMValueRef t,
+                              LLVMValueRef width,
+                              LLVMValueRef height,
+                              LLVMValueRef stride,
+                              LLVMValueRef data_ptr,
+                              LLVMValueRef *texel)
+{
+   LLVMBuilderRef builder = bld->builder;
+   struct lp_build_context i32, h16, u8n;
+   LLVMTypeRef i32_vec_type, h16_vec_type, u8n_vec_type;
+   LLVMValueRef f32_c256, i32_c8, i32_c128, i32_c255;
+   LLVMValueRef s_ipart, s_fpart, s_fpart_lo, s_fpart_hi;
+   LLVMValueRef t_ipart, t_fpart, t_fpart_lo, t_fpart_hi;
+   LLVMValueRef x0, x1;
+   LLVMValueRef y0, y1;
+   LLVMValueRef neighbors[2][2];
+   LLVMValueRef neighbors_lo[2][2];
+   LLVMValueRef neighbors_hi[2][2];
+   LLVMValueRef packed, packed_lo, packed_hi;
+   LLVMValueRef unswizzled[4];
+
+   lp_build_context_init(&i32, builder, lp_type_int(32));
+   lp_build_context_init(&h16, builder, lp_type_ufixed(16));
+   lp_build_context_init(&u8n, builder, lp_type_unorm(8));
+
+   i32_vec_type = lp_build_vec_type(i32.type);
+   h16_vec_type = lp_build_vec_type(h16.type);
+   u8n_vec_type = lp_build_vec_type(u8n.type);
+
+   f32_c256 = lp_build_const_scalar(bld->coord_type, 256.0);
+   s = lp_build_mul(&bld->coord_bld, s, f32_c256);
+   t = lp_build_mul(&bld->coord_bld, t, f32_c256);
+
+   s = LLVMBuildFPToSI(builder, s, i32_vec_type, "");
+   t = LLVMBuildFPToSI(builder, t, i32_vec_type, "");
+
+   i32_c128 = lp_build_int_const_scalar(i32.type, -128);
+   s = LLVMBuildAdd(builder, s, i32_c128, "");
+   t = LLVMBuildAdd(builder, t, i32_c128, "");
+
+   i32_c8 = lp_build_int_const_scalar(i32.type, 8);
+   s_ipart = LLVMBuildAShr(builder, s, i32_c8, "");
+   t_ipart = LLVMBuildAShr(builder, t, i32_c8, "");
+
+   i32_c255 = lp_build_int_const_scalar(i32.type, 255);
+   s_fpart = LLVMBuildAnd(builder, s, i32_c255, "");
+   t_fpart = LLVMBuildAnd(builder, t, i32_c255, "");
+
+   x0 = s_ipart;
+   y0 = t_ipart;
+
+   x0 = lp_build_sample_wrap(bld, x0, width,  bld->static_state->pot_width,  bld->static_state->wrap_s);
+   y0 = lp_build_sample_wrap(bld, y0, height, bld->static_state->pot_height, bld->static_state->wrap_t);
+
+   x1 = lp_build_add(&bld->int_coord_bld, x0, bld->int_coord_bld.one);
+   y1 = lp_build_add(&bld->int_coord_bld, y0, bld->int_coord_bld.one);
+
+   x1 = lp_build_sample_wrap(bld, x1, width,  bld->static_state->pot_width,  bld->static_state->wrap_s);
+   y1 = lp_build_sample_wrap(bld, y1, height, bld->static_state->pot_height, bld->static_state->wrap_t);
+
+   /*
+    * Transform 4 x i32 in
+    *
+    *   s_fpart = {s0, s1, s2, s3}
+    *
+    * into 8 x i16
+    *
+    *   s_fpart = {00, s0, 00, s1, 00, s2, 00, s3}
+    *
+    * into two 8 x i16
+    *
+    *   s_fpart_lo = {s0, s0, s0, s0, s1, s1, s1, s1}
+    *   s_fpart_hi = {s2, s2, s2, s2, s3, s3, s3, s3}
+    *
+    * and likewise for t_fpart. There is no risk of loosing precision here
+    * since the fractional parts only use the lower 8bits.
+    */
+
+   s_fpart = LLVMBuildBitCast(builder, s_fpart, h16_vec_type, "");
+   t_fpart = LLVMBuildBitCast(builder, t_fpart, h16_vec_type, "");
+
+   {
+      LLVMTypeRef elem_type = LLVMInt32Type();
+      LLVMValueRef shuffles_lo[LP_MAX_VECTOR_LENGTH];
+      LLVMValueRef shuffles_hi[LP_MAX_VECTOR_LENGTH];
+      LLVMValueRef shuffle_lo;
+      LLVMValueRef shuffle_hi;
+      unsigned i, j;
+
+      for(j = 0; j < h16.type.length; j += 4) {
+         unsigned subindex = util_cpu_caps.little_endian ? 0 : 1;
+         LLVMValueRef index;
+
+         index = LLVMConstInt(elem_type, j/2 + subindex, 0);
+         for(i = 0; i < 4; ++i)
+            shuffles_lo[j + i] = index;
+
+         index = LLVMConstInt(elem_type, h16.type.length/2 + j/2 + subindex, 0);
+         for(i = 0; i < 4; ++i)
+            shuffles_hi[j + i] = index;
+      }
+
+      shuffle_lo = LLVMConstVector(shuffles_lo, h16.type.length);
+      shuffle_hi = LLVMConstVector(shuffles_hi, h16.type.length);
+
+      s_fpart_lo = LLVMBuildShuffleVector(builder, s_fpart, h16.undef, shuffle_lo, "");
+      t_fpart_lo = LLVMBuildShuffleVector(builder, t_fpart, h16.undef, shuffle_lo, "");
+      s_fpart_hi = LLVMBuildShuffleVector(builder, s_fpart, h16.undef, shuffle_hi, "");
+      t_fpart_hi = LLVMBuildShuffleVector(builder, t_fpart, h16.undef, shuffle_hi, "");
+   }
+
+   /*
+    * Fetch the pixels as 4 x 32bit (rgba order might differ):
+    *
+    *   rgba0 rgba1 rgba2 rgba3
+    *
+    * bit cast them into 16 x u8
+    *
+    *   r0 g0 b0 a0 r1 g1 b1 a1 r2 g2 b2 a2 r3 g3 b3 a3
+    *
+    * unpack them into two 8 x i16:
+    *
+    *   r0 g0 b0 a0 r1 g1 b1 a1
+    *   r2 g2 b2 a2 r3 g3 b3 a3
+    *
+    * The higher 8 bits of the resulting elements will be zero.
+    */
+
+   neighbors[0][0] = lp_build_sample_packed(bld, x0, y0, stride, data_ptr);
+   neighbors[0][1] = lp_build_sample_packed(bld, x1, y0, stride, data_ptr);
+   neighbors[1][0] = lp_build_sample_packed(bld, x0, y1, stride, data_ptr);
+   neighbors[1][1] = lp_build_sample_packed(bld, x1, y1, stride, data_ptr);
+
+   neighbors[0][0] = LLVMBuildBitCast(builder, neighbors[0][0], u8n_vec_type, "");
+   neighbors[0][1] = LLVMBuildBitCast(builder, neighbors[0][1], u8n_vec_type, "");
+   neighbors[1][0] = LLVMBuildBitCast(builder, neighbors[1][0], u8n_vec_type, "");
+   neighbors[1][1] = LLVMBuildBitCast(builder, neighbors[1][1], u8n_vec_type, "");
+
+   lp_build_unpack2(builder, u8n.type, h16.type, neighbors[0][0], &neighbors_lo[0][0], &neighbors_hi[0][0]);
+   lp_build_unpack2(builder, u8n.type, h16.type, neighbors[0][1], &neighbors_lo[0][1], &neighbors_hi[0][1]);
+   lp_build_unpack2(builder, u8n.type, h16.type, neighbors[1][0], &neighbors_lo[1][0], &neighbors_hi[1][0]);
+   lp_build_unpack2(builder, u8n.type, h16.type, neighbors[1][1], &neighbors_lo[1][1], &neighbors_hi[1][1]);
+
+   /*
+    * Linear interpolate with 8.8 fixed point.
+    */
+
+   packed_lo = lp_build_lerp_2d(&h16,
+                                s_fpart_lo, t_fpart_lo,
+                                neighbors_lo[0][0],
+                                neighbors_lo[0][1],
+                                neighbors_lo[1][0],
+                                neighbors_lo[1][1]);
+
+   packed_hi = lp_build_lerp_2d(&h16,
+                                s_fpart_hi, t_fpart_hi,
+                                neighbors_hi[0][0],
+                                neighbors_hi[0][1],
+                                neighbors_hi[1][0],
+                                neighbors_hi[1][1]);
+
+   packed = lp_build_pack2(builder, h16.type, u8n.type, packed_lo, packed_hi);
+
+   /*
+    * Convert to SoA and swizzle.
+    */
+
+   packed = LLVMBuildBitCast(builder, packed, i32_vec_type, "");
+
+   lp_build_rgba8_to_f32_soa(bld->builder,
+                             bld->texel_type,
+                             packed, unswizzled);
+
+   lp_build_format_swizzle_soa(bld->format_desc,
+                               bld->texel_type, unswizzled,
+                               texel);
+}
+
+
+static void
 lp_build_sample_compare(struct lp_build_sample_context *bld,
                         LLVMValueRef p,
                         LLVMValueRef *texel)
@@ -336,7 +577,10 @@ lp_build_sample_soa(LLVMBuilderRef builder,
       break;
    case PIPE_TEX_FILTER_LINEAR:
    case PIPE_TEX_FILTER_ANISO:
-      lp_build_sample_2d_linear_soa(&bld, s, t, width, height, stride, data_ptr, texel);
+      if(lp_format_is_rgba8(bld.format_desc))
+         lp_build_sample_2d_linear_aos(&bld, s, t, width, height, stride, data_ptr, texel);
+      else
+         lp_build_sample_2d_linear_soa(&bld, s, t, width, height, stride, data_ptr, texel);
       break;
    default:
       assert(0);