i965: Prepare for using the ATTR register file in the fs backend

The scalar vertex shader will use the ATTR register file for vertex
attributes.  This patch adds support for the ATTR file to fs_visitor.

Signed-off-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

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

@@ -76,7 +76,7 @@ fs_inst::init(enum opcode opcode, uint8_t exec_size, const fs_reg &dst,
          this->exec_size = dst.width;
       } else {
          for (int i = 0; i < sources; ++i) {
-            if (src[i].file != GRF)
+            if (src[i].file != GRF && src[i].file != ATTR)
                continue;
 
             if (this->exec_size <= 1)
@@ -97,6 +97,7 @@ fs_inst::init(enum opcode opcode, uint8_t exec_size, const fs_reg &dst,
          break;
       case GRF:
       case HW_REG:
+      case ATTR:
          assert(this->src[i].width > 0);
          if (this->src[i].width == 1) {
             this->src[i].effective_width = this->exec_size;
@@ -121,6 +122,7 @@ fs_inst::init(enum opcode opcode, uint8_t exec_size, const fs_reg &dst,
    case GRF:
    case HW_REG:
    case MRF:
+   case ATTR:
       this->regs_written = (dst.width * dst.stride * type_sz(dst.type) + 31) / 32;
       break;
    case BAD_FILE:
@@ -3132,6 +3134,9 @@ fs_visitor::dump_instruction(backend_instruction *be_inst, FILE *file)
    case UNIFORM:
       fprintf(file, "***u%d***", inst->dst.reg + inst->dst.reg_offset);
       break;
+   case ATTR:
+      fprintf(file, "***attr%d***", inst->dst.reg + inst->dst.reg_offset);
+      break;
    case HW_REG:
       if (inst->dst.fixed_hw_reg.file == BRW_ARCHITECTURE_REGISTER_FILE) {
          switch (inst->dst.fixed_hw_reg.nr) {
@@ -3183,6 +3188,9 @@ fs_visitor::dump_instruction(backend_instruction *be_inst, FILE *file)
       case MRF:
          fprintf(file, "***m%d***", inst->src[i].reg);
          break;
+      case ATTR:
+         fprintf(file, "attr%d", inst->src[i].reg + inst->src[i].reg_offset);
+         break;
       case UNIFORM:
          fprintf(file, "u%d", inst->src[i].reg + inst->src[i].reg_offset);
          if (inst->src[i].reladdr) {

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

@@ -140,6 +140,7 @@ byte_offset(fs_reg reg, unsigned delta)
    case BAD_FILE:
       break;
    case GRF:
+   case ATTR:
       reg.reg_offset += delta / 32;
       break;
    case MRF:
@@ -165,6 +166,7 @@ horiz_offset(fs_reg reg, unsigned delta)
       break;
    case GRF:
    case MRF:
+   case ATTR:
       return byte_offset(reg, delta * reg.stride * type_sz(reg.type));
    default:
       assert(delta == 0);
@@ -181,6 +183,7 @@ offset(fs_reg reg, unsigned delta)
       break;
    case GRF:
    case MRF:
+   case ATTR:
       return byte_offset(reg, delta * reg.width * reg.stride * type_sz(reg.type));
    case UNIFORM:
       reg.reg_offset += delta;

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

@@ -107,8 +107,6 @@ brw_reg_from_fs_reg(fs_reg *reg)
       /* Probably unused. */
       brw_reg = brw_null_reg();
       break;
-   case UNIFORM:
-      unreachable("not reached");
    default:
       unreachable("not reached");
    }

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

@@ -197,8 +197,15 @@ fs_visitor::visit(ir_dereference_array *ir)
    src.type = brw_type_for_base_type(ir->type);
 
    if (constant_index) {
-      assert(src.file == UNIFORM || src.file == GRF || src.file == HW_REG);
+      if (src.file == ATTR) {
-      src = offset(src, constant_index->value.i[0] * element_size);
+         /* Attribute arrays get loaded as one vec4 per element.  In that case
+          * offset the source register.
+          */
+         src.reg += constant_index->value.i[0];
+      } else {
+         assert(src.file == UNIFORM || src.file == GRF || src.file == HW_REG);
+         src = offset(src, constant_index->value.i[0] * element_size);
+      }
    } else {
       /* Variable index array dereference.  We attach the variable index
        * component to the reg as a pointer to a register containing the
@@ -571,7 +578,8 @@ fs_visitor::visit(ir_expression *ir)
 	 ir->operands[operand]->fprint(stderr);
          fprintf(stderr, "\n");
       }
-      assert(this->result.file == GRF || this->result.file == UNIFORM);
+      assert(this->result.file == GRF ||
+             this->result.file == UNIFORM || this->result.file == ATTR);
       op[operand] = this->result;
 
       /* Matrix expression operands should have been broken down to vector