shader: Prefer roundEven in generated GLSL

There is no TGSI OPCODE for roundEven, prefer roundEven
so roundEven in guest gets translated to roundEven.

Signed-off-by: Lepton Wu <lepton@chromium.org>
Reviewed-by: Gert Wollny <gert.wollny@collabora.com>

src/vrend_shader.c

@@ -4839,6 +4839,12 @@ iter_instruction(struct tgsi_iterate_context *iter,
       emit_op1("floor");
       break;
    case TGSI_OPCODE_ROUND:
+      // There is no TGSI OPCODE for roundEven, prefer roundEven
+      // so roundEven in guest gets translated to roundEven.
+      if ((ctx->cfg->use_gles && ctx->cfg->glsl_version >= 300) ||
+          ctx->cfg->glsl_version >= 400)
+         emit_op1("roundEven");
+      else
          emit_op1("round");
       break;
    case TGSI_OPCODE_ISSG: