[Mesa-dev] [PATCH] i965/vec4: Don't coalesce registers in gen6 math ops if reswizzling needed

[Antia Puentes]

Math operations in SandyBridge do not support source swizzling

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92033
---
 src/mesa/drivers/dri/i965/brw_ir_vec4.h |  3 ++-
 src/mesa/drivers/dri/i965/brw_vec4.cpp  | 11 +++++++++--
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_ir_vec4.h b/src/mesa/drivers/dri/i965/brw_ir_vec4.h
index 966a410..a48bb68 100644
--- a/src/mesa/drivers/dri/i965/brw_ir_vec4.h
+++ b/src/mesa/drivers/dri/i965/brw_ir_vec4.h
@@ -175,7 +175,8 @@ public:
 
    bool is_send_from_grf();
    unsigned regs_read(unsigned arg) const;
-   bool can_reswizzle(int dst_writemask, int swizzle, int swizzle_mask);
+   bool can_reswizzle(const struct brw_device_info *devinfo, int dst_writemask,
+                      int swizzle, int swizzle_mask);
    void reswizzle(int dst_writemask, int swizzle);
    bool can_do_source_mods(const struct brw_device_info *devinfo);
 
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp
index ed49cd3..d7192e4 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
@@ -941,10 +941,17 @@ vec4_visitor::opt_set_dependency_control()
 }
 
 bool
-vec4_instruction::can_reswizzle(int dst_writemask,
+vec4_instruction::can_reswizzle(const struct brw_device_info *devinfo,
+                                int dst_writemask,
                                 int swizzle,
                                 int swizzle_mask)
 {
+
+   /* gen6 math instructions can not manage source swizzles */
+   if (devinfo->gen == 6 && is_math() &&
+       swizzle != BRW_SWIZZLE_XYZW)
+      return false;
+
    /* If this instruction sets anything not referenced by swizzle, then we'd
     * totally break it when we reswizzle.
     */
@@ -1077,7 +1084,7 @@ vec4_visitor::opt_register_coalesce()
                break;
 
             /* If we can't handle the swizzle, bail. */
-            if (!scan_inst->can_reswizzle(inst->dst.writemask,
+            if (!scan_inst->can_reswizzle(devinfo, inst->dst.writemask,
                                           inst->src[0].swizzle,
                                           chans_needed)) {
                break;
-- 
2.1.0