These lowering passes are optional for the backend to request, currently
the TGSI softpipe backend most likely the r600g backend would want to use
these passes as is. They aim to hit the gallium opcodes from the standard
rounding/truncation functions.
v2: also lower floor in mod_to_floor
Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
We want to restrict some lowering passes to floats only,
and enable other for doubles.
Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Currently, Mesa uses the lowering pass MOD_TO_FRACT to implement
mod(x,y) as y * fract(x/y). This implementation has a down side though:
it introduces precision errors due to the fract() operation. Even worse,
since the result of fract() is multiplied by y, the larger y gets the
larger the precision error we produce, so for large enough numbers the
precision loss is significant. Some examples on i965:
Operation Precision error
-----------------------------------------------------
mod(-1.951171875, 1.9980468750) 0.0000000447
mod(121.57, 13.29) 0.0000023842
mod(3769.12, 321.99) 0.0000762939
mod(3769.12, 1321.99) 0.0001220703
mod(-987654.125, 123456.984375) 0.0160663128
mod( 987654.125, 123456.984375) 0.0312500000
This patch replaces the current lowering pass with a different one
(MOD_TO_FLOOR) that follows the recommended implementation in the GLSL
man pages:
mod(x,y) = x - y * floor(x/y)
This implementation eliminates the precision errors at the expense of
an additional add instruction on some systems. On systems that can do
negate with multiply-add in a single operation this new implementation
would come at no additional cost.
v2 (Ian Romanick)
- Do not clone operands because when they are expressions we would be
duplicating them and that can lead to suboptimal code.
Fixes the following 16 dEQP tests:
dEQP-GLES3.functional.shaders.builtin_functions.precision.mod.mediump_*
dEQP-GLES3.functional.shaders.builtin_functions.precision.mod.highp_*
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
bitfieldInsert takes scalar integers for its last two arguments. Since
bitfieldInsert is lowered on i965 to two instructions that have more
flexible arguments, I didn't notice when I wrote this.
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Tt's kind of a trap---calling do_common_optimization() after
lower_instructions() may cause opt_algebraic() to reintroduce
ir_triop_lrp expressions that were lowered, effectively defeating the
point. Because of this, nobody uses it.
v2: Delete more code (caught by Ian Romanick).
Cc: "10.1" <mesa-stable@lists.freedesktop.org>
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Acked-by: Eric Anholt <eric@anholt.net>
This gives the compiler the chance to inline and not export class symbols
even in the absence of LTO. Saves about 60kb on disk.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@.intel.com>
i965/Gen7+ and Radeon/Evergreen+ have bfm/bfi instructions to implement
bitfieldInsert() from ARB_gpu_shader5.
v2: Add ir_binop_bfm and ir_triop_bfi to st_glsl_to_tgsi.cpp.
Remove spurious temporary assignment and dereference.
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>
Many GPUs have an instruction to do linear interpolation which is more
efficient than simply performing the algebra necessary (two multiplies,
an add, and a subtract).
Pattern matching or peepholing this is more desirable, but can be
tricky. By using an opcode, we can at least make shaders which use the
mix() built-in get the more efficient behavior.
Currently, all consumers lower ir_triop_lrp. Subsequent patches will
actually generate different code.
v2 [mattst88]:
- Add LRP_TO_ARITH flag to ir_to_mesa.cpp. Will be removed in a
subsequent patch and ir_triop_lrp translated directly.
v3 [mattst88]:
- Move changes from the next patch to opt_algebraic.cpp to accept
3-src operations.
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Using multiply and reciprocal for integer division involves potentially
lossy floating point conversions. This is okay for older GPUs that
represent integers as floating point, but undesirable for GPUs with
native integer division instructions.
TGSI, for example, has UDIV/IDIV instructions for integer division,
so it makes sense to handle this directly. Likewise for i965.
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Signed-off-by: Bryan Cain <bryancain3@gmail.com>
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
This patch fixes a bug when lowering an integer division:
x/y
to a multiplication by a reciprocal:
int(float(x)*reciprocal(float(y)))
If x was a plain int and y was an ivecN, the lowering pass
incorrectly assigned the type of the product to be float, when in fact
it should be vecN. This caused mesa to abort with an IR validation
error.
Fixes piglit tests {fs,vs}-op-div-int-ivec{2,3,4}.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
MOD_TO_FRACT was designed to lower the GLSL 1.20 mod() function, which
operates on floating point values. However, we also use ir_binop_mod
for GLSL 1.30's % operator, which operates on integers.
For now, make MOD_TO_FRACT only apply to floating-point mod operations.
In the future, we may want to add a lowering pass for integer-based mod.
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
f2i results in an int/ivec; we need i2u to get a uint/uvec.
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
This should save on the overhead of tree-walking and provide a
convenient place to add more instruction lowering in the future.
Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
