i965: Allow only one slot of clip distances to be set on Gen4-5.

The existing backend code assumed that if VARYING_SLOT_CLIP_DIST0
was written, then VARYING_SLOT_CLIP_DIST1 would be as well.  That's
true with the current lowering, but not necessary if there are 4 or
fewer clip distances.  Separate out the checks to allow this.

The new NIR-based lowering will trigger this case, which would have
caused backend validation errors (src is null) without this patch.

Reviewed-by: Eric Anholt <eric@anholt.net>

diff --git a/src/intel/compiler/brw_vec4_visitor.cpp b/src/intel/compiler/brw_vec4_visitor.cpp
index b2bb2c6b82ae39344816908b1c59a92a5f495dc4..aea64c5b54d539d1d7464762cb80d6e9af864c6c 100644 (file)
--- a/src/intel/compiler/brw_vec4_visitor.cpp
+++ b/src/intel/compiler/brw_vec4_visitor.cpp
@@ -1201,12 +1201,14 @@ vec4_visitor::emit_psiz_and_flags(dst_reg reg)
       if (output_reg[VARYING_SLOT_CLIP_DIST0][0].file != BAD_FILE) {
          current_annotation = "Clipping flags";
          dst_reg flags0 = dst_reg(this, glsl_type::uint_type);
-         dst_reg flags1 = dst_reg(this, glsl_type::uint_type);
 
          emit(CMP(dst_null_f(), src_reg(output_reg[VARYING_SLOT_CLIP_DIST0][0]), brw_imm_f(0.0f), BRW_CONDITIONAL_L));
          emit(VS_OPCODE_UNPACK_FLAGS_SIMD4X2, flags0, brw_imm_d(0));
          emit(OR(header1_w, src_reg(header1_w), src_reg(flags0)));
+      }
 
+      if (output_reg[VARYING_SLOT_CLIP_DIST1][0].file != BAD_FILE) {
+         dst_reg flags1 = dst_reg(this, glsl_type::uint_type);
          emit(CMP(dst_null_f(), src_reg(output_reg[VARYING_SLOT_CLIP_DIST1][0]), brw_imm_f(0.0f), BRW_CONDITIONAL_L));
          emit(VS_OPCODE_UNPACK_FLAGS_SIMD4X2, flags1, brw_imm_d(0));
          emit(SHL(flags1, src_reg(flags1), brw_imm_d(4)));