[Mesa-dev] [PATCH 1/4] r600: use min_dx10/max_dx10 instead of min/max

[Jan Vesely]

On Thu, 2017-11-09 at 18:26 +0100, Roland Scheidegger wrote:
> Am 09.11.2017 um 18:19 schrieb Jan Vesely:
> > On Thu, 2017-11-09 at 03:58 +0100, sroland at vmware.com wrote:
> > > From: Roland Scheidegger <sroland at vmware.com>
> > > 
> > > I believe this is the safe thing to do, especially ever since the driver
> > > actually generates NaNs for muls too.
> > > Albeit since the radeon ISA docs are inaccurate/wrong there, I'm not
> > > entirely sure what the non-dx10 versions do,
> > 
> > non-dx10 version return nan if one of the operands is nan (tested on
> > Turks).
> 
> Yes, I've modified a piglit test and came to the same conclusion. (I
> will put that up for review shortly.)
> I don't know why you'd ever want that, though (ieee fmin/fmax also
> should return non-nan).

opencl currently uses it to implement min/max since nans/infs inputs
are UB. dx10/ieee behaviour would also be OK, but maybe there's
difference in instruction latency?

Jan

> 
> Roland
> 
> 
> > 
> > Jan
> > 
> > >  but (as required by dx10)
> > > the dx10 versions should pick a non-nan source over a nan source.
> > > Other drivers presumably do the same (radeonsi, llvmpipe).
> > > This was shown to make some difference for bug 103544, albeit it is not
> > > required to fix it.
> > > ---
> > >  src/gallium/drivers/r600/r600_shader.c  | 12 ++++++------
> > >  src/gallium/drivers/r600/sb/sb_expr.cpp |  2 ++
> > >  2 files changed, 8 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/src/gallium/drivers/r600/r600_shader.c b/src/gallium/drivers/r600/r600_shader.c
> > > index 188fbc9d47..6a755bb3fd 100644
> > > --- a/src/gallium/drivers/r600/r600_shader.c
> > > +++ b/src/gallium/drivers/r600/r600_shader.c
> > > @@ -8844,8 +8844,8 @@ static const struct r600_shader_tgsi_instruction r600_shader_tgsi_instruction[]
> > >  	[TGSI_OPCODE_DP3]	= { ALU_OP2_DOT4_IEEE, tgsi_dp},
> > >  	[TGSI_OPCODE_DP4]	= { ALU_OP2_DOT4_IEEE, tgsi_dp},
> > >  	[TGSI_OPCODE_DST]	= { ALU_OP0_NOP, tgsi_opdst},
> > > -	[TGSI_OPCODE_MIN]	= { ALU_OP2_MIN, tgsi_op2},
> > > -	[TGSI_OPCODE_MAX]	= { ALU_OP2_MAX, tgsi_op2},
> > > +	[TGSI_OPCODE_MIN]	= { ALU_OP2_MIN_DX10, tgsi_op2},
> > > +	[TGSI_OPCODE_MAX]	= { ALU_OP2_MAX_DX10, tgsi_op2},
> > >  	[TGSI_OPCODE_SLT]	= { ALU_OP2_SETGT, tgsi_op2_swap},
> > >  	[TGSI_OPCODE_SGE]	= { ALU_OP2_SETGE, tgsi_op2},
> > >  	[TGSI_OPCODE_MAD]	= { ALU_OP3_MULADD_IEEE, tgsi_op3},
> > > @@ -9042,8 +9042,8 @@ static const struct r600_shader_tgsi_instruction eg_shader_tgsi_instruction[] =
> > >  	[TGSI_OPCODE_DP3]	= { ALU_OP2_DOT4_IEEE, tgsi_dp},
> > >  	[TGSI_OPCODE_DP4]	= { ALU_OP2_DOT4_IEEE, tgsi_dp},
> > >  	[TGSI_OPCODE_DST]	= { ALU_OP0_NOP, tgsi_opdst},
> > > -	[TGSI_OPCODE_MIN]	= { ALU_OP2_MIN, tgsi_op2},
> > > -	[TGSI_OPCODE_MAX]	= { ALU_OP2_MAX, tgsi_op2},
> > > +	[TGSI_OPCODE_MIN]	= { ALU_OP2_MIN_DX10, tgsi_op2},
> > > +	[TGSI_OPCODE_MAX]	= { ALU_OP2_MAX_DX10, tgsi_op2},
> > >  	[TGSI_OPCODE_SLT]	= { ALU_OP2_SETGT, tgsi_op2_swap},
> > >  	[TGSI_OPCODE_SGE]	= { ALU_OP2_SETGE, tgsi_op2},
> > >  	[TGSI_OPCODE_MAD]	= { ALU_OP3_MULADD_IEEE, tgsi_op3},
> > > @@ -9265,8 +9265,8 @@ static const struct r600_shader_tgsi_instruction cm_shader_tgsi_instruction[] =
> > >  	[TGSI_OPCODE_DP3]	= { ALU_OP2_DOT4_IEEE, tgsi_dp},
> > >  	[TGSI_OPCODE_DP4]	= { ALU_OP2_DOT4_IEEE, tgsi_dp},
> > >  	[TGSI_OPCODE_DST]	= { ALU_OP0_NOP, tgsi_opdst},
> > > -	[TGSI_OPCODE_MIN]	= { ALU_OP2_MIN, tgsi_op2},
> > > -	[TGSI_OPCODE_MAX]	= { ALU_OP2_MAX, tgsi_op2},
> > > +	[TGSI_OPCODE_MIN]	= { ALU_OP2_MIN_DX10, tgsi_op2},
> > > +	[TGSI_OPCODE_MAX]	= { ALU_OP2_MAX_DX10, tgsi_op2},
> > >  	[TGSI_OPCODE_SLT]	= { ALU_OP2_SETGT, tgsi_op2_swap},
> > >  	[TGSI_OPCODE_SGE]	= { ALU_OP2_SETGE, tgsi_op2},
> > >  	[TGSI_OPCODE_MAD]	= { ALU_OP3_MULADD_IEEE, tgsi_op3},
> > > diff --git a/src/gallium/drivers/r600/sb/sb_expr.cpp b/src/gallium/drivers/r600/sb/sb_expr.cpp
> > > index 3dd3a4815b..7a5d62c8e8 100644
> > > --- a/src/gallium/drivers/r600/sb/sb_expr.cpp
> > > +++ b/src/gallium/drivers/r600/sb/sb_expr.cpp
> > > @@ -753,7 +753,9 @@ bool expr_handler::fold_alu_op2(alu_node& n) {
> > >  				n.bc.src[0].abs == n.bc.src[1].abs) {
> > >  			switch (n.bc.op) {
> > >  			case ALU_OP2_MIN: // (MIN x, x) => (MOV x)
> > > +			case ALU_OP2_MIN_DX10:
> > >  			case ALU_OP2_MAX:
> > > +			case ALU_OP2_MAX_DX10:
> > >  				convert_to_mov(n, v0, n.bc.src[0].neg, n.bc.src[0].abs);
> > >  				return fold_alu_op1(n);
> > >  			case ALU_OP2_ADD:  // (ADD x, x) => (MUL x, 2)
> 
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