gallivm: Move gather functions to its own module.

They need to grow, and they provide basic functionality which is not
specific to sampling.

1 files changed, 148 insertions, 0 deletions

diff --git a/src/gallium/auxiliary/gallivm/lp_bld_gather.c b/src/gallium/auxiliary/gallivm/lp_bld_gather.c
new file mode 100644
index 00000000000..d60472e0656
--- /dev/null
+++ b/src/gallium/auxiliary/gallivm/lp_bld_gather.c
@@ -0,0 +1,148 @@
+/**************************************************************************
+ *
+ * Copyright 2010 VMware, Inc.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ **************************************************************************/
+
+
+#include "util/u_debug.h"
+#include "lp_bld_debug.h"
+#include "lp_bld_const.h"
+#include "lp_bld_format.h"
+#include "lp_bld_gather.h"
+
+
+/**
+ * Get the pointer to one element from scatter positions in memory.
+ *
+ * @sa lp_build_gather()
+ */
+LLVMValueRef
+lp_build_gather_elem_ptr(LLVMBuilderRef builder,
+                         unsigned length,
+                         LLVMValueRef base_ptr,
+                         LLVMValueRef offsets,
+                         unsigned i)
+{
+   LLVMValueRef offset;
+   LLVMValueRef ptr;
+
+   assert(LLVMTypeOf(base_ptr) == LLVMPointerType(LLVMInt8Type(), 0));
+
+   if (length == 1) {
+      assert(i == 0);
+      offset = offsets;
+   } else {
+      LLVMValueRef index = LLVMConstInt(LLVMInt32Type(), i, 0);
+      offset = LLVMBuildExtractElement(builder, offsets, index, "");
+   }
+
+   ptr = LLVMBuildGEP(builder, base_ptr, &offset, 1, "");
+
+   return ptr;
+}
+
+
+/**
+ * Gather one element from scatter positions in memory.
+ *
+ * @sa lp_build_gather()
+ */
+LLVMValueRef
+lp_build_gather_elem(LLVMBuilderRef builder,
+                     unsigned length,
+                     unsigned src_width,
+                     unsigned dst_width,
+                     LLVMValueRef base_ptr,
+                     LLVMValueRef offsets,
+                     unsigned i)
+{
+   LLVMTypeRef src_type = LLVMIntType(src_width);
+   LLVMTypeRef src_ptr_type = LLVMPointerType(src_type, 0);
+   LLVMTypeRef dst_elem_type = LLVMIntType(dst_width);
+   LLVMValueRef ptr;
+   LLVMValueRef res;
+
+   assert(LLVMTypeOf(base_ptr) == LLVMPointerType(LLVMInt8Type(), 0));
+
+   ptr = lp_build_gather_elem_ptr(builder, length, base_ptr, offsets, i);
+   ptr = LLVMBuildBitCast(builder, ptr, src_ptr_type, "");
+   res = LLVMBuildLoad(builder, ptr, "");
+
+   assert(src_width <= dst_width);
+   if (src_width > dst_width)
+      res = LLVMBuildTrunc(builder, res, dst_elem_type, "");
+   if (src_width < dst_width)
+      res = LLVMBuildZExt(builder, res, dst_elem_type, "");
+
+   return res;
+}
+
+
+/**
+ * Gather elements from scatter positions in memory into a single vector.
+ * Use for fetching texels from a texture.
+ * For SSE, typical values are length=4, src_width=32, dst_width=32.
+ *
+ * @param length length of the offsets
+ * @param src_width src element width in bits
+ * @param dst_width result element width in bits (src will be expanded to fit)
+ * @param base_ptr base pointer, should be a i8 pointer type.
+ * @param offsets vector with offsets
+ */
+LLVMValueRef
+lp_build_gather(LLVMBuilderRef builder,
+                unsigned length,
+                unsigned src_width,
+                unsigned dst_width,
+                LLVMValueRef base_ptr,
+                LLVMValueRef offsets)
+{
+   LLVMValueRef res;
+
+   if (length == 1) {
+      /* Scalar */
+      return lp_build_gather_elem(builder, length,
+                                  src_width, dst_width,
+                                  base_ptr, offsets, 0);
+   } else {
+      /* Vector */
+
+      LLVMTypeRef dst_elem_type = LLVMIntType(dst_width);
+      LLVMTypeRef dst_vec_type = LLVMVectorType(dst_elem_type, length);
+      unsigned i;
+
+      res = LLVMGetUndef(dst_vec_type);
+      for (i = 0; i < length; ++i) {
+         LLVMValueRef index = LLVMConstInt(LLVMInt32Type(), i, 0);
+         LLVMValueRef elem;
+         elem = lp_build_gather_elem(builder, length,
+                                     src_width, dst_width,
+                                     base_ptr, offsets, i);
+         res = LLVMBuildInsertElement(builder, res, elem, index, "");
+      }
+   }
+
+   return res;
+}