On 01/05/2017 06:37 PM, Marek Olšák wrote:
Shouldn't we also use abs for SQRT? For example, this adds abs for
both RSQ and SQRT:
https://cgit.freedesktop.org/~mareko/mesa/commit/?id=5e0fb661a8e6ac5f7b2245dd31595155128e0664
Yes, it makes more sense to do it for both even if we don't have any
open bug reports about SQRT. That could eventually happen in the future.
Marek
On Thu, Jan 5, 2017 at 5:47 PM, Samuel Pitoiset
<samuel.pitoi...@gmail.com> wrote:
As explained by Nicolai, it seems like D3D always compute the
absolute value while GLSL says that the result of inversesqrt()
is undefined if x <= 0. Using the absolute value looks like safer
especially when the game has been ported from D3D to GL.
This gets rid of the NaN values in the "Spec Ops: The Line" game
as well as the black squares.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97338
Signed-off-by: Samuel Pitoiset <samuel.pitoi...@gmail.com>
---
Nouveau also computes the absolute value before emitting RSQ.
src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c
b/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c
index 1966752cc0..ec6d6b0534 100644
--- a/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c
+++ b/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c
@@ -754,9 +754,12 @@ static void emit_rsq(const struct lp_build_tgsi_action
*action,
struct lp_build_tgsi_context *bld_base,
struct lp_build_emit_data *emit_data)
{
- LLVMValueRef sqrt =
- lp_build_emit_llvm_unary(bld_base, TGSI_OPCODE_SQRT,
- emit_data->args[0]);
+ LLVMValueRef abs, sqrt;
+
+ abs = lp_build_emit_llvm_unary(bld_base, TGSI_OPCODE_ABS,
+ emit_data->args[0]);
+
+ sqrt = lp_build_emit_llvm_unary(bld_base, TGSI_OPCODE_SQRT, abs);
emit_data->output[emit_data->chan] =
lp_build_emit_llvm_binary(bld_base, TGSI_OPCODE_DIV,
--
2.11.0
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