[Mesa-dev] [PATCH] r600/sb: Force ELSE path if the byte code started off with it

[Gert Wollny]

sb optimized away the ELSE in a construct like

   while (foo) {
      if (bar ) {
         do something;
      } else {
         break;
      }
   }

resulting in

   while (foo) {
      if (bar ) {
         do something;
         break;
      }
   }

which is obviously wrong.

With this patch an ELSE is inserted also if there was one before optimization.
This fixes piglit shaders at ssa@fs-if-def-else-break.

It might introduce a penalty by keeping an ELSE instruction when it can
actually be really optimized away though.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101442
---
I think there should be a better way to ensure that the else is inserted 
in this case, but so far it elluded me. 

I have no mesa-git write access. 

 src/gallium/drivers/r600/sb/sb_bc_finalize.cpp | 4 +---
 src/gallium/drivers/r600/sb/sb_bc_parser.cpp   | 5 ++++-
 src/gallium/drivers/r600/sb/sb_ir.h            | 3 ++-
 3 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/gallium/drivers/r600/sb/sb_bc_finalize.cpp b/src/gallium/drivers/r600/sb/sb_bc_finalize.cpp
index 099b295f18..4450247caf 100644
--- a/src/gallium/drivers/r600/sb/sb_bc_finalize.cpp
+++ b/src/gallium/drivers/r600/sb/sb_bc_finalize.cpp
@@ -208,9 +208,7 @@ void bc_finalizer::finalize_if(region_node* r) {
 		r->push_front(if_jump);
 		r->push_back(if_pop);
 
-		bool has_else = n_if->next;
-
-		if (has_else) {
+		if (n_if->has_else || n_if->next) {
 			cf_node *nelse = sh.create_cf(CF_OP_ELSE);
 			n_if->insert_after(nelse);
 			if_jump->jump(nelse);
diff --git a/src/gallium/drivers/r600/sb/sb_bc_parser.cpp b/src/gallium/drivers/r600/sb/sb_bc_parser.cpp
index 970e4141d5..f37067b8e2 100644
--- a/src/gallium/drivers/r600/sb/sb_bc_parser.cpp
+++ b/src/gallium/drivers/r600/sb/sb_bc_parser.cpp
@@ -959,8 +959,11 @@ int bc_parser::prepare_if(cf_node* c) {
 
 	c->insert_before(reg);
 
-	if (c_else != end)
+	if (c_else != end) {
+		n_if->has_else = true; 
 		dep->move(c_else, end);
+	}
+
 	dep2->move(c, end);
 
 	reg->push_back(dep);
diff --git a/src/gallium/drivers/r600/sb/sb_ir.h b/src/gallium/drivers/r600/sb/sb_ir.h
index bee947504e..af9b161597 100644
--- a/src/gallium/drivers/r600/sb/sb_ir.h
+++ b/src/gallium/drivers/r600/sb/sb_ir.h
@@ -1091,12 +1091,13 @@ public:
 
 class if_node : public container_node {
 protected:
-	if_node() : container_node(NT_IF, NST_LIST), cond() {};
+	if_node() : container_node(NT_IF, NST_LIST), cond(), has_else(false) {};
 public:
 	value *cond; // glued to pseudo output (dst[2]) of the PRED_SETxxx
 
 	virtual bool accept(vpass &p, bool enter);
 
+	bool has_else;
 	friend class shader;
 };
 
-- 
2.13.6