Mesa (master): spirv: fix visiting inner loops with same break/continue block

[Samuel Pitoiset]

Module: Mesa
Branch: master
Commit: 6bde8c560877512852ff49fafa296eb71a5ec14b
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=6bde8c560877512852ff49fafa296eb71a5ec14b

Author: Samuel Pitoiset <samuel.pitoiset at gmail.com>
Date:   Tue May 15 12:00:30 2018 +0200

spirv: fix visiting inner loops with same break/continue block

We should stop walking through the CFG when the inner loop's
break block ends up as the same block as the outer loop's
continue block because we are already going to visit it.

This fixes the following assertion which ends up by crashing
in RADV or ANV:

SPIR-V parsing FAILED:
In file ../src/compiler/spirv/vtn_cfg.c:381
block->node.link.next == NULL
0 bytes into the SPIR-V binary

This also fixes a crash with a camera shader from SteamVR.

v2: make use of vtn_get_branch_type() and add an assertion

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106090
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106504
CC: 18.0 18.1 <mesa-stable at lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

---

 src/compiler/spirv/vtn_cfg.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/compiler/spirv/vtn_cfg.c b/src/compiler/spirv/vtn_cfg.c
index e7d2f9ea61..ad4374112e 100644
--- a/src/compiler/spirv/vtn_cfg.c
+++ b/src/compiler/spirv/vtn_cfg.c
@@ -374,6 +374,19 @@ vtn_cfg_walk_blocks(struct vtn_builder *b, struct list_head *cf_list,
          vtn_cfg_walk_blocks(b, &loop->cont_body, new_loop_cont, NULL, NULL,
                              new_loop_break, NULL, block);
 
+         enum vtn_branch_type branch_type =
+            vtn_get_branch_type(b, new_loop_break, switch_case, switch_break,
+                                loop_break, loop_cont);
+
+         if (branch_type != vtn_branch_type_none) {
+            /* Stop walking through the CFG when this inner loop's break block
+             * ends up as the same block as the outer loop's continue block
+             * because we are already going to visit it.
+             */
+            vtn_assert(branch_type == vtn_branch_type_loop_continue);
+            return;
+         }
+
          block = new_loop_break;
          continue;
       }