[MLIR] Improve support for 0-dimensional Affine Maps.

[jbruestle]

Summary

Modified AffineMap::get to remove support for the overload which allowed
an ArrayRef of AffineExpr but no context (and gathered the context from a
presumed first entry, resulting in bugs when there were 0 results).

Instead, we support only a ArrayRef and a context, and a version which
takes a single AffineExpr.

Additionally, removed some now needless case logic which previously
special cased which call to AffineMap::get to use.

[rriddle]

mlir/include/mlir/Dialect/Utils/StructuredOpsUtils.h

34 ↗

(On Diff #257783)

Unrelated to this revision, but I don't see why this ArrayAttr needs to be generated.

mlir/lib/IR/AffineMap.cpp

130 ↗

(On Diff #257783)

nit: prefer empty instead of size.

mlir/lib/IR/Builders.cpp

300 ↗

(On Diff #257783)

Is this wrapped at 80 characters?

mlir/lib/Transforms/PipelineDataTransfer.cpp

102 ↗

(On Diff #257783)

Same here, is this formatted?

[flaub]

mlir/lib/Dialect/Vector/VectorTransforms.cpp

1350–1351

This comment appears obsolete.

[jbruestle]

Fixes from code review

[jbruestle]

Another minor issue found during review

[ftynse]

mlir/lib/Dialect/Linalg/IR/LinalgOps.cpp

527 ↗

(On Diff #257783)

Nit: consider adding a message to the assertion, as in assert(condition && "message")

[jbruestle]

Having issues with arcanist and git, attempting to resolve.

[jbruestle]

Trying to fix arc happy

mlir/lib/Dialect/Vector/VectorTransforms.cpp

static AffineMap adjustMap(AffineMap map, int64_t index,
     for (int64_t i = 0, e = map.getNumResults(); i < e; ++i) {
       int64_t idx = map.getResult(i).cast<AffineDimExpr>().getPosition();
       if (idx == index)
         continue;
       // Re-insert remaining indices, but renamed when occurring
       // after the removed index.
       auto targetExpr = getAffineDimExpr(idx < index ? idx : idx - 1, ctx);
       results.push_back(targetExpr);
     }
-    // The (...) -> () affine map has its own factory method.
     return AffineMap::get(map.getNumDims() - 1, 0, results, ctx);
   }
 
   // Helper to drop dimension from vector type.
   static Type adjustType(VectorType tp, int64_t index) {
     int64_t rank = tp.getRank();
     Type eltType = tp.getElementType();
     if (rank == 1) {
       assert(index == 0 && "index for scalar result out of bounds");