Mesa (10.4): r600g/sb: fix issues cause by GLSL switching to loops for switch

[Emil Velikov]

Module: Mesa
Branch: 10.4
Commit: b5cc04b6ade33738166d6a3d5d4aab3eae5eb4cc
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=b5cc04b6ade33738166d6a3d5d4aab3eae5eb4cc

Author: Dave Airlie <airlied at redhat.com>
Date:   Fri Nov 28 00:49:48 2014 +0000

r600g/sb: fix issues cause by GLSL switching to loops for switch

Since 73dd50acf6d244979c2a657906aa56d3ac60d550
glsl: implement switch flow control using a loop

The SB backend was falling over in an assert or crashing.

Tracked this down to the loops having no repeats, but requiring
a working break, initial code just called the loop handler for
all non-if statements, but this caused a regression in
tests/shaders/dead-code-break-interaction.shader_test.
So I had to add further code to detect if all the departure
nodes are empty and avoid generating an empty loop for that case.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=86089
Cc: "10.4" <mesa-stable at lists.freedesktop.org>
Reviewed-By: Glenn Kennard <glenn.kennard at gmail.com>
Signed-off-by: Dave Airlie <airlied at redhat.com>
(cherry picked from commit 7b0067d23a6f64cf83c42e7f11b2cd4100c569fe)

---

 src/gallium/drivers/r600/sb/sb_bc_finalize.cpp |   50 ++++++++++++++++++------
 1 file changed, 38 insertions(+), 12 deletions(-)

diff --git a/src/gallium/drivers/r600/sb/sb_bc_finalize.cpp b/src/gallium/drivers/r600/sb/sb_bc_finalize.cpp
index f0849ca..0fa0910 100644
--- a/src/gallium/drivers/r600/sb/sb_bc_finalize.cpp
+++ b/src/gallium/drivers/r600/sb/sb_bc_finalize.cpp
@@ -46,15 +46,22 @@ int bc_finalizer::run() {
 	for (regions_vec::reverse_iterator I = rv.rbegin(), E = rv.rend(); I != E;
 			++I) {
 		region_node *r = *I;
-
+		bool is_if = false;
 		assert(r);
 
-		bool loop = r->is_loop();
+		assert(r->first);
+		if (r->first->is_container()) {
+			container_node *repdep1 = static_cast<container_node*>(r->first);
+			assert(repdep1->is_depart() || repdep1->is_repeat());
+			if_node *n_if = static_cast<if_node*>(repdep1->first);
+			if (n_if && n_if->is_if())
+				is_if = true;
+		}
 
-		if (loop)
-			finalize_loop(r);
-		else
+		if (is_if)
 			finalize_if(r);
+		else
+			finalize_loop(r);
 
 		r->expand();
 	}
@@ -112,16 +119,33 @@ void bc_finalizer::finalize_loop(region_node* r) {
 
 	cf_node *loop_start = sh.create_cf(CF_OP_LOOP_START_DX10);
 	cf_node *loop_end = sh.create_cf(CF_OP_LOOP_END);
+	bool has_instr = false;
+
+	if (!r->is_loop()) {
+		for (depart_vec::iterator I = r->departs.begin(), E = r->departs.end();
+		     I != E; ++I) {
+			depart_node *dep = *I;
+			if (!dep->empty()) {
+				has_instr = true;
+				break;
+			}
+		}
+	} else
+		has_instr = true;
 
-	loop_start->jump_after(loop_end);
-	loop_end->jump_after(loop_start);
+	if (has_instr) {
+		loop_start->jump_after(loop_end);
+		loop_end->jump_after(loop_start);
+	}
 
 	for (depart_vec::iterator I = r->departs.begin(), E = r->departs.end();
 			I != E; ++I) {
 		depart_node *dep = *I;
-		cf_node *loop_break = sh.create_cf(CF_OP_LOOP_BREAK);
-		loop_break->jump(loop_end);
-		dep->push_back(loop_break);
+		if (has_instr) {
+			cf_node *loop_break = sh.create_cf(CF_OP_LOOP_BREAK);
+			loop_break->jump(loop_end);
+			dep->push_back(loop_break);
+		}
 		dep->expand();
 	}
 
@@ -137,8 +161,10 @@ void bc_finalizer::finalize_loop(region_node* r) {
 		rep->expand();
 	}
 
-	r->push_front(loop_start);
-	r->push_back(loop_end);
+	if (has_instr) {
+		r->push_front(loop_start);
+		r->push_back(loop_end);
+	}
 }
 
 void bc_finalizer::finalize_if(region_node* r) {