i965/nir: Validate that NIR passes call nir_metadata_preserve().

Failing to call nir_metadata_preserve() can have nasty consequences:
some pass breaks dominance information, but leaves it marked as valid,
causing some subsequent pass to go haywire and probably crash.

This pass adds a simple validation mechanism to ensure passes handle
this properly.  We add a new bogus metadata flag that isn't used for
anything in particular, set it before each pass, and ensure it *isn't*
still set after the pass.  nir_metadata_preserve will reset the flag,
so correct passes will work, and bad passes will assert fail.

(I would have made these functions static inline, but nir.h is included
in C++, so we can't bit-or enums without lots of casting...)

Thanks to Dylan Baker for the idea.

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Jason Ekstrand <[email protected]>
Reviewed-by: Iago Toral Quiroga <[email protected]>

1 files changed, 7 insertions, 3 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_nir.c b/src/mesa/drivers/dri/i965/brw_nir.c
index b19f9691956..7826729db85 100644
--- a/src/mesa/drivers/dri/i965/brw_nir.c
+++ b/src/mesa/drivers/dri/i965/brw_nir.c
@@ -178,9 +178,13 @@ brw_nir_lower_outputs(nir_shader *nir, bool is_scalar)
    this_progress;             \
 }))
 
-#define OPT(pass, ...) _OPT(                 \
-   this_progress = pass(nir ,##__VA_ARGS__); \
-   progress = progress || this_progress;     \
+#define OPT(pass, ...) _OPT(                   \
+   nir_metadata_set_validation_flag(nir);      \
+   this_progress = pass(nir ,##__VA_ARGS__);   \
+   if (this_progress) {                        \
+      progress = true;                         \
+      nir_metadata_check_validation_flag(nir); \
+   }                                           \
 )
 
 #define OPT_V(pass, ...) _OPT( \