Mesa (master): nir: Make nir_[cf_node/instr]_[prev/next] return null if at the end

[Jason Ekstrand]

Module: Mesa
Branch: master
Commit: 3d25afc51c1d56fe8c29147825e53ba272780360
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=3d25afc51c1d56fe8c29147825e53ba272780360

Author: Jason Ekstrand <jason.ekstrand at intel.com>
Date:   Wed Feb  4 21:22:45 2015 -0800

nir: Make nir_[cf_node/instr]_[prev/next] return null if at the end

Reviewed-by: Connor Abbott <cwabbott0 at gmail.com>

---

 src/glsl/nir/nir.h |   28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 7f6e241..b4cccb9 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -416,15 +416,23 @@ typedef struct {
 } nir_instr;
 
 static inline nir_instr *
-nir_instr_next(const nir_instr *instr)
+nir_instr_next(nir_instr *instr)
 {
-   return exec_node_data(nir_instr, (instr)->node.next, node);
+   struct exec_node *next = exec_node_get_next(&instr->node);
+   if (exec_node_is_tail_sentinel(next))
+      return NULL;
+   else
+      return exec_node_data(nir_instr, next, node);
 }
 
 static inline nir_instr *
-nir_instr_prev(const nir_instr *instr)
+nir_instr_prev(nir_instr *instr)
 {
-   return exec_node_data(nir_instr, (instr)->node.prev, node);
+   struct exec_node *prev = exec_node_get_prev(&instr->node);
+   if (exec_node_is_head_sentinel(prev))
+      return NULL;
+   else
+      return exec_node_data(nir_instr, prev, node);
 }
 
 typedef struct {
@@ -1272,13 +1280,21 @@ typedef struct {
 static inline nir_cf_node *
 nir_cf_node_next(nir_cf_node *node)
 {
-   return exec_node_data(nir_cf_node, exec_node_get_next(&node->node), node);
+   struct exec_node *next = exec_node_get_next(&node->node);
+   if (exec_node_is_tail_sentinel(next))
+      return NULL;
+   else
+      return exec_node_data(nir_cf_node, next, node);
 }
 
 static inline nir_cf_node *
 nir_cf_node_prev(nir_cf_node *node)
 {
-   return exec_node_data(nir_cf_node, exec_node_get_prev(&node->node), node);
+   struct exec_node *prev = exec_node_get_prev(&node->node);
+   if (exec_node_is_head_sentinel(prev))
+      return NULL;
+   else
+      return exec_node_data(nir_cf_node, prev, node);
 }
 
 static inline bool