[Mesa-dev] [PATCH] i965/fs: Check for compilation failure and bail before optimizing.

[Kenneth Graunke]

Prior to this patch, it would attempt to optimize and allocate registers
for the program even if it failed to compile.  This seems wasteful.

More importantly, the "message length > 11" failure seems to choke the
instruction scheduler, making it somehow use an undefined value and
segmentation fault.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_fs.cpp |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

Eric,

Yeah.  Somehow I wasn't thinking straight and thought that'd check for
failure after every instruction.  But it doesn't; those are only the
top-level variable declarations and functions.  No sense in that at all.

This version moves it below the loop---after the bulk of codegen, but
prior to optimizing and register allocation.  Seems reasonable.

The 16-element stack array theory sounds about right.  Presumably we
should never run into that limit for good code, and this ought to reject
the bad code.

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 7c73a8f..3a16afe 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -1533,6 +1533,8 @@ fs_visitor::run()
 	 this->result = reg_undef;
 	 ir->accept(this);
       }
+      if (failed)
+	 return false;
 
       emit_fb_writes();
 
-- 
1.7.5.4