src/gallium/auxiliary/gallivm/lp_bld_gather.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2010 VMware, Inc.
   4  * All Rights Reserved.
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  11  * permit persons to whom the Software is furnished to do so, subject to
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  13  *
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  15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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  22  * The above copyright notice and this permission notice (including the
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  24  * of the Software.
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  26  **************************************************************************/
  27
  28
  29 #include "util/u_debug.h"
  30 #include "lp_bld_debug.h"
  31 #include "lp_bld_const.h"
  32 #include "lp_bld_format.h"
  33 #include "lp_bld_gather.h"
  34 #include "lp_bld_init.h"
  35 #include "lp_bld_intr.h"
  36
  37
  38 /**
  39  * Get the pointer to one element from scatter positions in memory.
  40  *
  41  * @sa lp_build_gather()
  42  */
  43 LLVMValueRef
  44 lp_build_gather_elem_ptr(struct gallivm_state *gallivm,
  45                          unsigned length,
  46                          LLVMValueRef base_ptr,
  47                          LLVMValueRef offsets,
  48                          unsigned i)
  49 {
  50    LLVMValueRef offset;
  51    LLVMValueRef ptr;
  52
  53    assert(LLVMTypeOf(base_ptr) == LLVMPointerType(LLVMInt8TypeInContext(gallivm->context), 0));
  54
  55    if (length == 1) {
  56       assert(i == 0);
  57       offset = offsets;
  58    } else {
  59       LLVMValueRef index = lp_build_const_int32(gallivm, i);
  60       offset = LLVMBuildExtractElement(gallivm->builder, offsets, index, "");
  61    }
  62
  63    ptr = LLVMBuildGEP(gallivm->builder, base_ptr, &offset, 1, "");
  64
  65    return ptr;
  66 }
  67
  68
  69 /**
  70  * Gather one element from scatter positions in memory.
  71  *
  72  * @sa lp_build_gather()
  73  */
  74 LLVMValueRef
  75 lp_build_gather_elem(struct gallivm_state *gallivm,
  76                      unsigned length,
  77                      unsigned src_width,
  78                      unsigned dst_width,
  79                      boolean aligned,
  80                      LLVMValueRef base_ptr,
  81                      LLVMValueRef offsets,
  82                      unsigned i,
  83                      boolean vector_justify)
  84 {
  85    LLVMTypeRef src_type = LLVMIntTypeInContext(gallivm->context, src_width);
  86    LLVMTypeRef src_ptr_type = LLVMPointerType(src_type, 0);
  87    LLVMTypeRef dst_elem_type = LLVMIntTypeInContext(gallivm->context, dst_width);
  88    LLVMValueRef ptr;
  89    LLVMValueRef res;
  90
  91    assert(LLVMTypeOf(base_ptr) == LLVMPointerType(LLVMInt8TypeInContext(gallivm->context), 0));
  92
  93    ptr = lp_build_gather_elem_ptr(gallivm, length, base_ptr, offsets, i);
  94    ptr = LLVMBuildBitCast(gallivm->builder, ptr, src_ptr_type, "");
  95    res = LLVMBuildLoad(gallivm->builder, ptr, "");
  96
  97    /* XXX
  98     * On some archs we probably really want to avoid having to deal
  99     * with alignments lower than 4 bytes (if fetch size is a power of
 100     * two >= 32). On x86 it doesn't matter, however.
 101     * We should be able to guarantee full alignment for any kind of texture
 102     * fetch (except ARB_texture_buffer_range, oops), but not vertex fetch
 103     * (there's PIPE_CAP_VERTEX_BUFFER_OFFSET_4BYTE_ALIGNED_ONLY and friends
 104     * but I don't think that's quite what we wanted).
 105     * For ARB_texture_buffer_range, PIPE_CAP_TEXTURE_BUFFER_OFFSET_ALIGNMENT
 106     * looks like a good fit, but it seems this cap bit (and OpenGL) aren't
 107     * enforcing what we want (which is what d3d10 does, the offset needs to
 108     * be aligned to element size, but GL has bytes regardless of element
 109     * size which would only leave us with minimum alignment restriction of 16
 110     * which doesn't make much sense if the type isn't 4x32bit). Due to
 111     * translation of offsets to first_elem in sampler_views it actually seems
 112     * gallium could not do anything else except 16 no matter what...
 113     */
 114   if (!aligned) {
 115       LLVMSetAlignment(res, 1);
 116    }
 117
 118    assert(src_width <= dst_width);
 119    if (src_width > dst_width) {
 120       res = LLVMBuildTrunc(gallivm->builder, res, dst_elem_type, "");
 121    } else if (src_width < dst_width) {
 122       res = LLVMBuildZExt(gallivm->builder, res, dst_elem_type, "");
 123       if (vector_justify) {
 124 #ifdef PIPE_ARCH_BIG_ENDIAN
 125          res = LLVMBuildShl(gallivm->builder, res,
 126                             LLVMConstInt(dst_elem_type, dst_width - src_width, 0), "");
 127 #endif
 128       }
 129    }
 130
 131    return res;
 132 }
 133
 134
 135 /**
 136  * Gather elements from scatter positions in memory into a single vector.
 137  * Use for fetching texels from a texture.
 138  * For SSE, typical values are length=4, src_width=32, dst_width=32.
 139  *
 140  * When src_width < dst_width, the return value can be justified in
 141  * one of two ways:
 142  * "integer justification" is used when the caller treats the destination
 143  * as a packed integer bitmask, as described by the channels' "shift" and
 144  * "width" fields;
 145  * "vector justification" is used when the caller casts the destination
 146  * to a vector and needs channel X to be in vector element 0.
 147  *
 148  * @param length length of the offsets
 149  * @param src_width src element width in bits
 150  * @param dst_width result element width in bits (src will be expanded to fit)
 151  * @param aligned whether the data is guaranteed to be aligned (to src_width)
 152  * @param base_ptr base pointer, should be a i8 pointer type.
 153  * @param offsets vector with offsets
 154  * @param vector_justify select vector rather than integer justification
 155  */
 156 LLVMValueRef
 157 lp_build_gather(struct gallivm_state *gallivm,
 158                 unsigned length,
 159                 unsigned src_width,
 160                 unsigned dst_width,
 161                 boolean aligned,
 162                 LLVMValueRef base_ptr,
 163                 LLVMValueRef offsets,
 164                 boolean vector_justify)
 165 {
 166    LLVMValueRef res;
 167
 168    if (length == 1) {
 169       /* Scalar */
 170       return lp_build_gather_elem(gallivm, length,
 171                                   src_width, dst_width, aligned,
 172                                   base_ptr, offsets, 0, vector_justify);
 173    } else {
 174       /* Vector */
 175
 176       LLVMTypeRef dst_elem_type = LLVMIntTypeInContext(gallivm->context, dst_width);
 177       LLVMTypeRef dst_vec_type = LLVMVectorType(dst_elem_type, length);
 178       unsigned i;
 179
 180       res = LLVMGetUndef(dst_vec_type);
 181       for (i = 0; i < length; ++i) {
 182          LLVMValueRef index = lp_build_const_int32(gallivm, i);
 183          LLVMValueRef elem;
 184          elem = lp_build_gather_elem(gallivm, length,
 185                                      src_width, dst_width, aligned,
 186                                      base_ptr, offsets, i, vector_justify);
 187          res = LLVMBuildInsertElement(gallivm->builder, res, elem, index, "");
 188       }
 189    }
 190
 191    return res;
 192 }
 193
 194 LLVMValueRef
 195 lp_build_gather_values(struct gallivm_state * gallivm,
 196                        LLVMValueRef * values,
 197                        unsigned value_count)
 198 {
 199    LLVMTypeRef vec_type = LLVMVectorType(LLVMTypeOf(values[0]), value_count);
 200    LLVMBuilderRef builder = gallivm->builder;
 201    LLVMValueRef vec = LLVMGetUndef(vec_type);
 202    unsigned i;
 203
 204    for (i = 0; i < value_count; i++) {
 205       LLVMValueRef index = lp_build_const_int32(gallivm, i);
 206       vec = LLVMBuildInsertElement(builder, vec, values[i], index, "");
 207    }
 208    return vec;
 209 }