intel/fs: Disable SIMD32 dispatch on Gen4-6 with control flow

The hardware's control flow logic is 16-wide so we're out of luck
here.  We could, in theory, support SIMD32 if we know the control-flow
is uniform but we don't have that information at this point.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Matt Turner <mattst88@gmail.com>

diff --git a/src/intel/compiler/brw_fs_nir.cpp b/src/intel/compiler/brw_fs_nir.cpp
index e324519..9273b30 100644 (file)
--- a/src/intel/compiler/brw_fs_nir.cpp
+++ b/src/intel/compiler/brw_fs_nir.cpp
@@ -385,6 +385,10 @@ fs_visitor::nir_emit_if(nir_if *if_stmt)
    nir_emit_cf_list(&if_stmt->else_list);
 
    bld.emit(BRW_OPCODE_ENDIF);
+
+   if (devinfo->gen < 7)
+      limit_dispatch_width(16, "Non-uniform control flow unsupported "
+                           "in SIMD32 mode.");
 }
 
 void
@@ -395,6 +399,10 @@ fs_visitor::nir_emit_loop(nir_loop *loop)
    nir_emit_cf_list(&loop->body);
 
    bld.emit(BRW_OPCODE_WHILE);
+
+   if (devinfo->gen < 7)
+      limit_dispatch_width(16, "Non-uniform control flow unsupported "
+                           "in SIMD32 mode.");
 }
 
 void