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authorMarek Olšák <[email protected]>2016-05-30 17:43:26 +0200
committerMarek Olšák <[email protected]>2016-06-06 22:50:55 +0200
commit589d6b58c3355f3ff8e5bef4b3f5e94b479cc96b (patch)
tree9e0a5878b71f82f51f459829bc46855a9f2eeae9 /src
parent991cbfcb1459f3adce13d70c383f9c4c6fd4ee96 (diff)
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 <[email protected]>
Diffstat (limited to 'src')
-rw-r--r--src/mesa/state_tracker/st_glsl_to_tgsi.cpp16
1 files 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: