There are some algebraic transformations that we want to do but only if
certain things are constants. For instance, we may want to replace
a * (b + c) with (a * b) + (a * c) as long as a and either b or c is constant.
While this generates more instructions, some of it will get constant
folded.
nir_algebraic.py doesn't handle this yet, but that's ok because the C
language will make sure that false is the default for now.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This framework provides a simple way to do simple search-and-replace
operations on NIR code. The nir_search.h header provides four simple data
structures for representing expressions: nir_value and four subtypes:
nir_variable, nir_constant, and nir_expression. An expression tree can
then be represented by nesting these data structures as needed. The
nir_replace_instr function takes an instruction, an expression, and a
value; if the instruction matches the expression, it is replaced with a new
chain of instructions to generate the given replacement value. The
framework keeps track of swizzles on sources and automatically generates
the currect swizzles for the replacement value.
Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
