Mesa (glsl2): glsl2: Do ir_if_return on the way out, not the way in.

[Eric Anholt]

Module: Mesa
Branch: glsl2
Commit: 0cf545ec696ab450c3f5ee65d7a0c2a5d9dca409
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=0cf545ec696ab450c3f5ee65d7a0c2a5d9dca409

Author: Eric Anholt <eric at anholt.net>
Date:   Thu Jul 29 15:49:14 2010 -0700

glsl2: Do ir_if_return on the way out, not the way in.

The problem with doing it on the way in is that for a function with
multiple early returns, we'll move an outer block in, then restart the
pass, then move the two inside returns out, then never move outer
blocks in again because the remaining early returns are inside an else
block and they don't know that there's a return just after their
block.  By going inside-out, we get the early returns stacked up so
that they all move out with a series of
move_returns_after_block().

Fixes (on i965):
glsl-fs-raytrace-bug27060
glsl-vs-raytrace-bug26691

---

 src/glsl/ir_if_return.cpp |   39 ++++++++++++++++++++-------------------
 1 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/src/glsl/ir_if_return.cpp b/src/glsl/ir_if_return.cpp
index 293f7aa..5ab8759 100644
--- a/src/glsl/ir_if_return.cpp
+++ b/src/glsl/ir_if_return.cpp
@@ -44,10 +44,10 @@ public:
    }
 
    ir_visitor_status visit_enter(ir_function_signature *);
-   ir_visitor_status visit_enter(ir_if *);
+   ir_visitor_status visit_leave(ir_if *);
 
-   void move_outer_block_inside(ir_instruction *ir,
-				exec_list *inner_block);
+   ir_visitor_status move_outer_block_inside(ir_instruction *ir,
+					     exec_list *inner_block);
    void move_returns_after_block(ir_instruction *ir,
 				 ir_return *then_return,
 				 ir_return *else_return);
@@ -127,18 +127,25 @@ ir_if_return_visitor::move_returns_after_block(ir_instruction *ir,
    this->progress = true;
 }
 
-void
+ir_visitor_status
 ir_if_return_visitor::move_outer_block_inside(ir_instruction *ir,
 					      exec_list *inner_block)
 {
-   if (!ir->get_next()->is_tail_sentinel())
-      this->progress = true;
+   if (!ir->get_next()->is_tail_sentinel()) {
+      while (!ir->get_next()->is_tail_sentinel()) {
+	 ir_instruction *move_ir = (ir_instruction *)ir->get_next();
 
-   while (!ir->get_next()->is_tail_sentinel()) {
-      ir_instruction *move_ir = (ir_instruction *)ir->get_next();
+	 move_ir->remove();
+	 inner_block->push_tail(move_ir);
+      }
 
-      move_ir->remove();
-      inner_block->push_tail(move_ir);
+      /* If we move the instructions following ir inside the block, it
+       * will confuse the exec_list iteration in the parent that visited
+       * us.  So stop the visit at this point.
+       */
+      return visit_stop;
+   } else {
+      return visit_continue;
    }
 }
 
@@ -199,7 +206,7 @@ ir_if_return_visitor::visit_enter(ir_function_signature *ir)
 }
 
 ir_visitor_status
-ir_if_return_visitor::visit_enter(ir_if *ir)
+ir_if_return_visitor::visit_leave(ir_if *ir)
 {
    ir_return *then_return;
    ir_return *else_return;
@@ -231,15 +238,9 @@ ir_if_return_visitor::visit_enter(ir_if *ir)
     * side, so we'll trigger the above case on the next pass.
     */
    if (then_return) {
-      move_outer_block_inside(ir, &ir->else_instructions);
+      return move_outer_block_inside(ir, &ir->else_instructions);
    } else {
       assert(else_return);
-      move_outer_block_inside(ir, &ir->then_instructions);
+      return move_outer_block_inside(ir, &ir->then_instructions);
    }
-
-   /* If we move the instructions following ir inside the block, it
-    * will confuse the exec_list iteration in the parent that visited
-    * us.  So stop the visit at this point.
-    */
-   return visit_stop;
 }