Reviewed-by: Chris Forbes <chr...@ijw.co.nz> On Aug 17, 2014 10:14 AM, "Kenneth Graunke" <kenn...@whitecape.org> wrote:
> The optimization relies on CMP setting the destination to 0, which is > equivalent to 0.0f. However, early platforms only set the least > significant byte, leaving the other bits undefined. So, we must disable > the optimization on those platforms. > > Oddly, Sandybridge wasn't reported as broken, even though it's > documented to only set the LSB. It's unclear whether it follows ILK on > IVB behavior. > > +32 piglits on Ironlake. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?=79963 > Signed-off-by: Kenneth Graunke <kenn...@whitecape.org> > --- > src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp > b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp > index f22d38d..33cb9a9 100644 > --- a/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp > +++ b/src/mesa/drivers/dri/i965/brw_vec4_visitor.cpp > @@ -1135,6 +1135,13 @@ vec4_visitor::try_emit_mad(ir_expression *ir) > bool > vec4_visitor::try_emit_b2f_of_compare(ir_expression *ir) > { > + /* This optimization relies on CMP setting the destination to 0 when > + * false. Early hardware only sets the least significant bit, and > + * leaves the other bits undefined. So we can't use it. > + */ > + if (brw->gen < 7) > + return false; > + > ir_expression *const cmp = ir->operands[0]->as_expression(); > > if (cmp == NULL) > -- > 1.9.2 > > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/mesa-dev >
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