Mesa (master): i965: Allow exec_list sentinels as arguments to insert functions.

[Matt Turner]

Module: Mesa
Branch: master
Commit: 1af5c4a526ab27ee2e4c5be96148af231f217c25
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=1af5c4a526ab27ee2e4c5be96148af231f217c25

Author: Matt Turner <mattst88 at gmail.com>
Date:   Tue Feb 17 18:01:41 2015 -0800

i965: Allow exec_list sentinels as arguments to insert functions.

To insert an instruction at the end of a basic block, we typically do
something like

   inst = block->last_non_control_flow_inst();
   inst->insert_after(block, new_inst);

But blocks can consist of a single control flow instruction, so inst
will actually be the exec_list's head sentinel. We shouldn't use it as
if it were a regular instruction, but it is safe to insert something after
it.

This patch avoids assert-failing because an exec_list sentinel wasn't in
the basic block's instruction list.

Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

---

 src/mesa/drivers/dri/i965/brw_shader.cpp |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_shader.cpp b/src/mesa/drivers/dri/i965/brw_shader.cpp
index 83734a2..5781c6b 100644
--- a/src/mesa/drivers/dri/i965/brw_shader.cpp
+++ b/src/mesa/drivers/dri/i965/brw_shader.cpp
@@ -993,7 +993,8 @@ adjust_later_block_ips(bblock_t *start_block, int ip_adjustment)
 void
 backend_instruction::insert_after(bblock_t *block, backend_instruction *inst)
 {
-   assert(inst_is_in_block(block, this) || !"Instruction not in block");
+   if (!this->is_head_sentinel())
+      assert(inst_is_in_block(block, this) || !"Instruction not in block");
 
    block->end_ip++;
 
@@ -1005,7 +1006,8 @@ backend_instruction::insert_after(bblock_t *block, backend_instruction *inst)
 void
 backend_instruction::insert_before(bblock_t *block, backend_instruction *inst)
 {
-   assert(inst_is_in_block(block, this) || !"Instruction not in block");
+   if (!this->is_tail_sentinel())
+      assert(inst_is_in_block(block, this) || !"Instruction not in block");
 
    block->end_ip++;