[Mesa-dev] [PATCH] draw_llvm: fix segfaults on non-SSE2 CPUs where it is disabled

[Luca Barbieri]

Currently draw_llvm refuses to create itself on non-SSE2 CPUs due to
an alleged LLVM bug.

However, this is implemented improperly, because other parts of draw
still attempt to access draw->llvm, resulting in segfaults.

Instead, put the check in debug_get_option_draw_use_llvm, check that
before calling draw_llvm_create, and then check whether draw->llvm is
non-null everywhere else.
---
 src/gallium/auxiliary/draw/draw_context.c |   37 ++++++++++++++++++++++++----
 src/gallium/auxiliary/draw/draw_llvm.c    |    7 -----
 src/gallium/auxiliary/draw/draw_pt.c      |    5 +---
 3 files changed, 32 insertions(+), 17 deletions(-)

diff --git a/src/gallium/auxiliary/draw/draw_context.c b/src/gallium/auxiliary/draw/draw_context.c
index 995b675..565d7f5 100644
--- a/src/gallium/auxiliary/draw/draw_context.c
+++ b/src/gallium/auxiliary/draw/draw_context.c
@@ -34,6 +34,7 @@
 #include "pipe/p_context.h"
 #include "util/u_memory.h"
 #include "util/u_math.h"
+#include "util/u_cpu_detect.h"
 #include "draw_context.h"
 #include "draw_vs.h"
 #include "draw_gs.h"
@@ -41,6 +42,25 @@
 #if HAVE_LLVM
 #include "gallivm/lp_bld_init.h"
 #include "draw_llvm.h"
+
+static boolean
+debug_get_option_draw_use_llvm(void)
+{
+   static boolean first = TRUE;
+   static boolean value;
+   if (first) {
+      first = FALSE;
+      value = debug_get_bool_option("DRAW_USE_LLVM", TRUE);
+
+#ifdef PIPE_ARCH_X86
+      util_cpu_detect();
+      /* require SSE2 due to LLVM PR6960. */
+      if (!util_cpu_caps.has_sse2)
+         value = FALSE;
+#endif
+   }
+   return value;
+}
 #endif
 
 struct draw_context *draw_create( struct pipe_context *pipe )
@@ -50,10 +70,13 @@ struct draw_context *draw_create( struct pipe_context *pipe )
       goto fail;
 
 #if HAVE_LLVM
-   lp_build_init();
-   assert(lp_build_engine);
-   draw->engine = lp_build_engine;
-   draw->llvm = draw_llvm_create(draw);
+   if(debug_get_option_draw_use_llvm())
+   {
+      lp_build_init();
+      assert(lp_build_engine);
+      draw->engine = lp_build_engine;
+      draw->llvm = draw_llvm_create(draw);
+   }
 #endif
 
    if (!draw_init(draw))
@@ -135,7 +158,8 @@ void draw_destroy( struct draw_context *draw )
    draw_vs_destroy( draw );
    draw_gs_destroy( draw );
 #ifdef HAVE_LLVM
-   draw_llvm_destroy( draw->llvm );
+   if(draw->llvm)
+      draw_llvm_destroy( draw->llvm );
 #endif
 
    FREE( draw );
@@ -659,7 +683,8 @@ draw_set_mapped_texture(struct draw_context *draw,
                         const void *data[DRAW_MAX_TEXTURE_LEVELS])
 {
 #ifdef HAVE_LLVM
-   draw_llvm_set_mapped_texture(draw,
+   if(draw->llvm)
+      draw_llvm_set_mapped_texture(draw,
                                 sampler_idx,
                                 width, height, depth, last_level,
                                 row_stride, img_stride, data);
diff --git a/src/gallium/auxiliary/draw/draw_llvm.c b/src/gallium/auxiliary/draw/draw_llvm.c
index 8d53601..58d3e34 100644
--- a/src/gallium/auxiliary/draw/draw_llvm.c
+++ b/src/gallium/auxiliary/draw/draw_llvm.c
@@ -210,13 +210,6 @@ draw_llvm_create(struct draw_context *draw)
 {
    struct draw_llvm *llvm;
 
-#ifdef PIPE_ARCH_X86
-   util_cpu_detect();
-   /* require SSE2 due to LLVM PR6960. */
-   if (!util_cpu_caps.has_sse2)
-       return NULL;
-#endif
-
    llvm = CALLOC_STRUCT( draw_llvm );
    if (!llvm)
       return NULL;
diff --git a/src/gallium/auxiliary/draw/draw_pt.c b/src/gallium/auxiliary/draw/draw_pt.c
index 2489275..d237edc 100644
--- a/src/gallium/auxiliary/draw/draw_pt.c
+++ b/src/gallium/auxiliary/draw/draw_pt.c
@@ -43,9 +43,6 @@
 
 DEBUG_GET_ONCE_BOOL_OPTION(draw_fse, "DRAW_FSE", FALSE)
 DEBUG_GET_ONCE_BOOL_OPTION(draw_no_fse, "DRAW_NO_FSE", FALSE)
-#ifdef HAVE_LLVM
-DEBUG_GET_ONCE_BOOL_OPTION(draw_use_llvm, "DRAW_USE_LLVM", TRUE)
-#endif
 
 static unsigned trim( unsigned count, unsigned first, unsigned incr )
 {
@@ -164,7 +161,7 @@ boolean draw_pt_init( struct draw_context *draw )
       return FALSE;
 
 #if HAVE_LLVM
-   if (debug_get_option_draw_use_llvm())
+   if (draw->llvm)
       draw->pt.middle.llvm = draw_pt_fetch_pipeline_or_emit_llvm( draw );
 #endif
 
-- 
1.7.0.4