This CL starts by replacing AffineExpr* with value-type AffineExprRef in a few
places in the IR. By a domino effect that is pretty telling of the
inconsistencies in the codebase, const is removed where it makes sense.
The rationale is that the decision was concisously made that unique'd types
have pointer semantics without const specifier. This is fine but we should be
consistent. In the end, the only logical invariant is that there should never
be such a thing as a const AffineExpr*, const AffineMap* or const IntegerSet*
in our codebase.
This CL takes a number of shortcuts to killing const with fire, in particular
forcing const AffineExprRef to return the underlying non-const
AffineExpr*. This will be removed once AffineExpr* has disappeared in
containers but for now such shortcuts allow a bit of sanity in this long quest
for cleanups.
The **only** places where const AffineExpr*, const AffineMap* or const
IntegerSet* may still appear is by transitive needs from containers,
comparison operators etc.
There is still one major thing remaining here: figure out why cast/dyn_cast
return me a const AffineXXX*, which in turn requires a bunch of ugly
const_casts. I suspect this is due to the classof
taking const AffineXXXExpr*. I wonder whether this is a side effect of 1., if
it is coming from llvm itself (I'd doubt it) or something else (clattner@?)
In light of this, the whole discussion about const makes total sense to me now
and I would systematically apply the rule that in the end, we should never
have any const XXX in our codebase for unique'd types (assuming we can remove
them all in containers and no additional constness constraint is added on us
from the outside world).
PiperOrigin-RevId: 215811554
This CL implements AffineExprBaseRef as a templated type to allow LLVM-style
casts to work properly. This also allows making AffineExprBaseRef::expr
private.
To achieve this, it is necessary to use llvm::simplify_type and make
AffineConstExpr derive from both AffineExpr and llvm::simplify<AffineExprRef>.
Note that llvm::simplify_type is just an interface to enable the proper
template resolution of isa/cast/dyn_cast but it otherwise holds no value.
Lastly note that certain dyn_cast operations wanted the const AffineExpr* form
of AffineExprBaseRef so I made the implicit constructor take that by default
and documented the immutable behavior. I think this is consistent with the
decision to make unique'd type immutable by convention and never use const on
them.
PiperOrigin-RevId: 215642247
This CL uniformizes the uses of AffineExprWrap outside of IR.
The public API of AffineExpr builder is modified to only use AffineExprWrap.
A few places access AffineExprWrap.expr, this is only while the API is in
transition to easily keep track (i.e. make expr private and let the compiler
track the errors).
Parser.cpp exhibits patterns that are dependent on nullptr values so
converting it is left for another CL.
PiperOrigin-RevId: 215642005
- introduce mlir::{floorDiv, ceilDiv, mod} for constant inputs in
mlir/Support/MathExtras.h
- consistently use these everywhere in IR, Analysis, and Transforms.
PiperOrigin-RevId: 215580677
Use these methods to simplify existing code. Rename getConstantMap
getConstantAffineMap. Move declarations to group similar ones together.
PiperOrigin-RevId: 212814829
unroll/unroll-and-jam more powerful; add additional affine expr builder methods
- use previously added analysis/simplification to infer multiple of unroll
factor trip counts, making loop unroll/unroll-and-jam more general.
- for loop unroll, support bounds that are single result affine map's with the
same set of operands. For unknown loop bounds, loop unroll will now work as
long as trip count can be determined to be a multiple of unroll factor.
- extend getConstantTripCount to deal with single result affine map's with the
same operands. move it to mlir/Analysis/LoopAnalysis.cpp
- add additional builder utility methods for affine expr arithmetic
(difference, mod/floordiv/ceildiv w.r.t postitive constant). simplify code to
use the utility methods.
- move affine analysis routines to AffineAnalysis.cpp/.h from
AffineStructures.cpp/.h.
- Rename LoopUnrollJam to LoopUnrollAndJam to match class name.
- add an additional simplification for simplifyFloorDiv, simplifyCeilDiv
- Rename AffineMap::getNumOperands() getNumInputs: an affine map by itself does
not have operands. Operands are passed to it through affine_apply, from loop
bounds/if condition's, etc., operands are stored in the latter.
This should be sufficiently powerful for now as far as unroll/unroll-and-jam go for TPU
code generation, and can move to other analyses/transformations.
Loop nests like these are now unrolled without any cleanup loop being generated.
for %i = 1 to 100 {
// unroll factor 4: no cleanup loop will be generated.
for %j = (d0) -> (d0) (%i) to (d0) -> (5*d0 + 3) (%i) {
%x = "foo"(%j) : (affineint) -> i32
}
}
for %i = 1 to 100 {
// unroll factor 4: no cleanup loop will be generated.
for %j = (d0) -> (d0) (%i) to (d0) -> (d0 - d mod 4 - 1) (%i) {
%y = "foo"(%j) : (affineint) -> i32
}
}
for %i = 1 to 100 {
for %j = (d0) -> (d0) (%i) to (d0) -> (d0 + 128) (%i) {
%x = "foo"() : () -> i32
}
}
TODO(bondhugula): extend this to LoopUnrollAndJam as well in the next CL (with minor
changes).
PiperOrigin-RevId: 212661212
Outside of IR/
- simplify a MutableAffineMap by flattening the affine expressions
- add a simplify affine expression pass that uses this analysis
- update the FlatAffineConstraints API (to be used in the next CL)
In IR:
- add isMultipleOf and getKnownGCD for AffineExpr, and make the in-IR
simplication of simplifyMod simpler and more powerful.
- rename the AffineExpr visitor methods to distinguish b/w visiting and
walking, and to simplify API names based on context.
The next CL will use some of these for the loop unrolling/unroll-jam to make
the detection for the need of cleanup loop powerful/non-trivial.
A future CL will finally move this simplification to FlatAffineConstraints to
make it more powerful. For eg., currently, even if a mod expr appearing in a
part of the expression tree can't be simplified, the whole thing won't be
simplified.
PiperOrigin-RevId: 211012256
This revamps implementation of the loop bounds in the ForStmt, using general representation that supports operands. The frequent case of constant bounds is supported
via special access methods.
This also includes:
- Operand iterators for the Statement class.
- OpPointer::is() method to query the class of the Operation.
- Support for the bound shorthand notation parsing and printing.
- Validity checks for the bound operands used as dim ids and symbols
I didn't mean this CL to be so large. It just happened this way, as one thing led to another.
PiperOrigin-RevId: 210204858
FlatAffineConstraints, and MutableAffineMap.
All four classes introduced reside in lib/Analysis and are not meant to be
used in the IR (from lib/IR or lib/Parser/). They are all mutable, alloc'ed,
dealloc'ed - although with their fields pointing to immutable affine
expressions (AffineExpr *).
While on this, update simplifyMod to fold mod to a zero when possible.
PiperOrigin-RevId: 209618437
- simplify operations with identity elements (multiply by 1, add with 0).
- simplify successive add/mul: fold constants, propagate constants to the
right.
- simplify floordiv and ceildiv when divisors are constants, and the LHS is a
multiply expression with RHS constant.
- fix an affine expression printing bug on paren emission.
- while on this, fix affine-map test cases file (memref's using layout maps
that were duplicates of existing ones should be emitted pointing to the
unique'd one).
PiperOrigin-RevId: 207046738
- Drop sub-classing of affine binary op expressions.
- Drop affine expr op kind sub. Represent it as multiply by -1 and add. This
will also be in line with the math form when we'll need to represent a system of
linear equalities/inequalities: the negative number goes into the coefficient
of an affine form. (For eg. x_1 + (-1)*x_2 + 3*x_3 + (-2) >= 0). The folding
simplification will transparently deal with multiplying the -1 with any other
constants. This also means we won't need to simplify a multiply expression
like in x_1 + (-2)*x_2 to a subtract expression (x_1 - 2*x_2) for
canonicalization/uniquing.
- When we print the IR, we will still pretty print to a subtract when possible.
PiperOrigin-RevId: 205298958
- fold constants when possible.
- for a mul expression, canonicalize to always keep the LHS as the
constant/symbolic term, and similarly, the RHS for an add expression to keep
it closer to the mathematical form. (Eg: f(x) = 3*x + 5)); other similar simplifications;
- verify binary op expressions at creation time.
TODO: we can completely drop AffineSubExpr, and instead use add and mul by -1.
This way something like x - 4 and -4 + x get canonicalized to x + -1 * 4
instead of being x - 4 and x + -4. (The other alternative if wanted to retain
AffineSubExpr would be to simplify x + -1*y to x - y and x + <neg number> to x
- <pos number>).
PiperOrigin-RevId: 204240258
- check for non-affine expressions
- handle negative numbers and negation of id's, expressions
- functions to check if a map is pure affine or semi-affine
- simplify/clean up affine map parsing code
- report more errors messages, more accurate error messages
PiperOrigin-RevId: 203773633
A recursive descent parser for affine maps/expressions with operator precedence and
associativity. (While on this, sketch out uniqui'ing functionality for affine maps
and affine binary op expressions (partly).)
PiperOrigin-RevId: 203222063
Run test case:
$ mlir-opt test/IR/parser-affine-map.mlir
test/IR/parser-affine-map.mlir:3:30: error: expect '(' at start of map range
#hello_world2 (i, j) [s0] -> i+s0, j)
^
PiperOrigin-RevId: 202736856
- parsing affine map identifiers
- place-holder classes for AffineMap
- module contains a list of affine maps (defined at the top level).
PiperOrigin-RevId: 202336919
Nicolas Vasilache