[mlir][Python][linalg] Fix to limit size of SmallVector.

[gysit]

Summary

Stack allocate at most two ScalarAssign elements. Using the default number of inlined elements triggered a static assert in some setups (https://reviews.llvm.org/D102075).

[mehdi_amini]

That seems fairly ad-hoc as a fix: what are the conditions where this is a problem more precisely?

[NathanielMcVicar]

In D102827#2771837, @mehdi_amini wrote:

That seems fairly ad-hoc as a fix: what are the conditions where this is a problem more precisely?

I was only able to repro on Windows debug. See here: https://reviews.llvm.org/D102075#2769791

[gysit]

In D102827#2771837, @mehdi_amini wrote:

That seems fairly ad-hoc as a fix: what are the conditions where this is a problem more precisely?

On some systems (windows debug) ScalarAssign is > 256 bytes. On Linux we are slightly below. For example, since the nested std::vector carries more debug info. In case the struct continuous to grow we probably want to switch to std::vector.

mlir/tools/mlir-linalg-ods-gen/mlir-linalg-ods-yaml-gen.cpp

struct ScalarAssign {
   std::string arg;
   ScalarExpression value;
 };
 
 struct LinalgStructuredOpConfig {
   SmallVector<LinalgTensorDef> args;
   LinalgIndexingMapsConfig indexingMaps;
   SmallVector<LinalgIteratorTypeDef> iteratorTypes;
-  SmallVector<ScalarAssign> assignments;
+  SmallVector<ScalarAssign, 2> assignments;
 };
 
 struct LinalgOpConfig {
   Optional<LinalgOpMetadata> metadata;
   Optional<LinalgStructuredOpConfig> structuredOp;
 };
 
 } // namespace