i965/fs: Factor out texture offset bitfield computation.

We'll want to reuse this for the VS, and it's complex enough that I'd
rather not cut and paste it.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/mesa/drivers/dri/i965/brw_fs_visitor.cpp

@@ -1077,24 +1077,7 @@ fs_visitor::visit(ir_texture *ir)
    fs_reg coordinate = this->result;
 
    if (ir->offset != NULL) {
-      ir_constant *offset = ir->offset->as_constant();
-      assert(offset != NULL);
-
-      signed char offsets[3];
-      for (unsigned i = 0; i < ir->offset->type->vector_elements; i++)
-	 offsets[i] = (signed char) offset->value.i[i];
-
-      /* Combine all three offsets into a single unsigned dword:
-       *
-       *    bits 11:8 - U Offset (X component)
-       *    bits  7:4 - V Offset (Y component)
-       *    bits  3:0 - R Offset (Z component)
-       */
-      unsigned offset_bits = 0;
-      for (unsigned i = 0; i < ir->offset->type->vector_elements; i++) {
-	 const unsigned shift = 4 * (2 - i);
-	 offset_bits |= (offsets[i] << shift) & (0xF << shift);
-      }
+      uint32_t offset_bits = brw_texture_offset(ir->offset->as_constant());
 
       /* Explicitly set up the message header by copying g0 to msg reg m1. */
       emit(BRW_OPCODE_MOV, fs_reg(MRF, 1, BRW_REGISTER_TYPE_UD),

src/mesa/drivers/dri/i965/brw_shader.cpp

@@ -239,3 +239,26 @@ brw_math_function(enum opcode op)
       return 0;
    }
 }
+
+uint32_t
+brw_texture_offset(ir_constant *offset)
+{
+   assert(offset != NULL);
+
+   signed char offsets[3];
+   for (unsigned i = 0; i < offset->type->vector_elements; i++)
+      offsets[i] = (signed char) offset->value.i[i];
+
+   /* Combine all three offsets into a single unsigned dword:
+    *
+    *    bits 11:8 - U Offset (X component)
+    *    bits  7:4 - V Offset (Y component)
+    *    bits  3:0 - R Offset (Z component)
+    */
+   unsigned offset_bits = 0;
+   for (unsigned i = 0; i < offset->type->vector_elements; i++) {
+      const unsigned shift = 4 * (2 - i);
+      offset_bits |= (offsets[i] << shift) & (0xF << shift);
+   }
+   return offset_bits;
+}

src/mesa/drivers/dri/i965/brw_shader.h

@@ -23,9 +23,11 @@
 
 #include <stdint.h>
 #include "brw_defines.h"
+#include "glsl/ir.h"
 
 #pragma once
 
 int brw_type_for_base_type(const struct glsl_type *type);
 uint32_t brw_conditional_for_comparison(unsigned int op);
 uint32_t brw_math_function(enum opcode op);
+uint32_t brw_texture_offset(ir_constant *offset);