compiler/list: avoid downcasting sentinel nodes (v2)

This avoids undefined behaviour that crashes gcc's ubsan.

v2: don't add a new macro (Ian Romanick)

2 files changed, 10 insertions, 7 deletions

diff --git a/src/compiler/glsl/opt_dead_code_local.cpp b/src/compiler/glsl/opt_dead_code_local.cpp
index d38fd2bf63..a35026e4c9 100644
--- a/src/compiler/glsl/opt_dead_code_local.cpp
+++ b/src/compiler/glsl/opt_dead_code_local.cpp
@@ -291,7 +291,8 @@ dead_code_local_basic_block(ir_instruction *first,
 			     ir_instruction *last,
 			     void *data)
 {
-   ir_instruction *ir, *ir_next;
+   ir_instruction *ir;
+   exec_node *ir_next;
    /* List of avaialble_copy */
    exec_list assignments;
    bool *out_progress = (bool *)data;
@@ -299,8 +300,8 @@ dead_code_local_basic_block(ir_instruction *first,
 
    void *ctx = ralloc_context(NULL);
    /* Safe looping, since process_assignment */
-   for (ir = first, ir_next = (ir_instruction *)first->next;;
-	ir = ir_next, ir_next = (ir_instruction *)ir->next) {
+   for (ir = first, ir_next = first->next;;
+        ir = (ir_instruction *) ir_next, ir_next = ir->next) {
       ir_assignment *ir_assign = ir->as_assignment();
 
       if (debug) {
@@ -315,6 +316,7 @@ dead_code_local_basic_block(ir_instruction *first,
 	 ir->accept(&kill);
       }
 
+      /* break before we might perform an incorrect cast of a sentinel node */
       if (ir == last)
 	 break;
    }
diff --git a/src/compiler/glsl/opt_tree_grafting.cpp b/src/compiler/glsl/opt_tree_grafting.cpp
index a40e5f7160..b9db41befa 100644
--- a/src/compiler/glsl/opt_tree_grafting.cpp
+++ b/src/compiler/glsl/opt_tree_grafting.cpp
@@ -347,11 +347,12 @@ tree_grafting_basic_block(ir_instruction *bb_first,
 			  void *data)
 {
    struct tree_grafting_info *info = (struct tree_grafting_info *)data;
-   ir_instruction *ir, *next;
+   exec_node *node, *next;
 
-   for (ir = bb_first, next = (ir_instruction *)ir->next;
-	ir != bb_last->next;
-	ir = next, next = (ir_instruction *)ir->next) {
+   for (node = bb_first, next = node->next;
+        node != bb_last->next;
+        node = next, next = node->next) {
+      ir_instruction * const ir = (ir_instruction *) node;
       ir_assignment *assign = ir->as_assignment();
 
       if (!assign)