[Mesa-dev] [PATCH v2] i965/skl: Disable SIMD16 when 3-source instructions are used

[Neil Roberts]

Steppings C0 and D0 of Skylake fail when using SIMD16 with 3-source
instructions (such as MAD). This patch just makes it disable SIMD16 in
those cases.

This implements WaDisableSIMD16On3SrcInstr and fixes ~190 Piglit
tests.

v2: Also apply on stepping D0
---

Damien Lespiau pointed out that the workaround also needs to be
applied on stepping D0.

 src/mesa/drivers/dri/i965/brw_fs.cpp | 22 ++++++++++++++++++++++
 src/mesa/drivers/dri/i965/brw_fs.h   |  1 +
 2 files changed, 23 insertions(+)

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 533feb4..b61208b 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -3729,6 +3729,27 @@ fs_visitor::fixup_3src_null_dest()
    }
 }
 
+/**
+ * 3-source instructions don't work on Skylake steppings C0 and D0. If the
+ * revision isn't known then it will take the safe option and disable it in
+ * case it's one of those. Implements WaDisableSIMD16On3SrcInstr.
+ */
+void
+fs_visitor::disable_simd16_with_3src()
+{
+   if (brw->gen != 9 ||
+       (brw->revision != 2 && brw->revision != 3 && brw->revision != -1))
+      return;
+
+   foreach_block_and_inst_safe (block, fs_inst, inst, cfg) {
+      if (inst->is_3src()) {
+         no16("SIMD16 doesn't work with 3-source instructions on "
+              "Gen9 steppings C0 and D0\n");
+         return;
+      }
+   }
+}
+
 void
 fs_visitor::allocate_registers()
 {
@@ -3910,6 +3931,7 @@ fs_visitor::run_fs()
       assign_urb_setup();
 
       fixup_3src_null_dest();
+      disable_simd16_with_3src();
       allocate_registers();
 
       if (failed)
diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h
index 70098d8..7091b9f 100644
--- a/src/mesa/drivers/dri/i965/brw_fs.h
+++ b/src/mesa/drivers/dri/i965/brw_fs.h
@@ -196,6 +196,7 @@ public:
    void setup_payload_gen6();
    void setup_vs_payload();
    void fixup_3src_null_dest();
+   void disable_simd16_with_3src();
    void assign_curb_setup();
    void calculate_urb_setup();
    void assign_urb_setup();
-- 
1.9.3