glsl2: Add ir_assignment::write_mask and associated methods

Replace swizzles on the LHS with additional swizzles on the RHS and a
write mask in the assignment instruction.  As part of this add
ir_assignment::set_lhs.  Ideally we'd make ir_assignment::lhs private
to prevent erroneous writes, but that would require a lot of code
butchery at this point.

Add ir_assignment constructor that takes an explicit write mask.  This
is required for ir_assignment::clone, but it can also be used in other
places.  Without this, ir_assignment clones lose their write masks,
and incorrect IR is generated in optimization passes.

Add ir_assignment::whole_variable_written method.  This method gets
the variable on the LHS if the whole variable is written or NULL
otherwise.  This is different from
ir->lhs->whole_variable_referenced() because the latter has no
knowledge of the write mask stored in the ir_assignment.

Gut all code from ir_to_mesa that handled swizzles on the LHS of
assignments.  There is probably some other refactoring that could be
done here, but that can be left for another day.

1 files changed, 13 insertions, 1 deletions

diff --git a/src/glsl/ir_print_visitor.cpp b/src/glsl/ir_print_visitor.cpp
index 73476e7e9b6..39b11bb32cc 100644
--- a/src/glsl/ir_print_visitor.cpp
+++ b/src/glsl/ir_print_visitor.cpp
@@ -296,7 +296,19 @@ void ir_print_visitor::visit(ir_assignment *ir)
    else
       printf("(constant bool (1))");
 
-   printf(" ");
+
+   char mask[5];
+   unsigned j = 0;
+
+   for (unsigned i = 0; i < 4; i++) {
+      if ((ir->write_mask & (1 << i)) != 0) {
+	 mask[j] = "xyzw"[i];
+	 j++;
+      }
+   }
+   mask[j] = '\0';
+
+   printf(" (%s) ", mask);
 
    ir->lhs->accept(this);