From 589d6b58c3355f3ff8e5bef4b3f5e94b479cc96b Mon Sep 17 00:00:00 2001 From: =?utf8?q?Marek=20Ol=C5=A1=C3=A1k?= Date: Mon, 30 May 2016 17:43:26 +0200 Subject: [PATCH] st/mesa: change SQRT lowering to fix the game Risen Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94627 (against nouveau) Acked-by: Ilia Mirkin --- src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp index 91a0a26de82..06eb6f159b0 100644 --- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp +++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp @@ -1901,13 +1901,15 @@ glsl_to_tgsi_visitor::visit_expression(ir_expression* ir, st_src_reg *op) if (have_sqrt) { emit_scalar(ir, TGSI_OPCODE_SQRT, result_dst, op[0]); } else { - /* sqrt(x) = x * rsq(x). */ - emit_scalar(ir, TGSI_OPCODE_RSQ, result_dst, op[0]); - emit_asm(ir, TGSI_OPCODE_MUL, result_dst, result_src, op[0]); - /* For incoming channels <= 0, set the result to 0. */ - op[0].negate = ~op[0].negate; - emit_asm(ir, TGSI_OPCODE_CMP, result_dst, - op[0], result_src, st_src_reg_for_float(0.0)); + /* This is the only instruction sequence that makes the game "Risen" + * render correctly. ABS is not required for the game, but since GLSL + * declares negative values as "undefined", allowing us to do whatever + * we want, I choose to use ABS to match DX9 and pre-GLSL RSQ + * behavior. + */ + emit_scalar(ir, TGSI_OPCODE_ABS, result_dst, op[0]); + emit_scalar(ir, TGSI_OPCODE_RSQ, result_dst, result_src); + emit_scalar(ir, TGSI_OPCODE_RCP, result_dst, result_src); } break; case ir_unop_rsq: -- 2.30.2