[mlir][spirv] Implement vector type legalization for function signatures (#98337)

### Description
This PR implements a minimal version of function signature conversion to
unroll vectors into 1D and with a size supported by SPIR-V (2, 3 or 4
depending on the original dimension). This PR also includes new unit
tests that only check for function signature conversion.

### Future Plans
- Check for capabilities that support vectors of size 8 or 16.
- Set up `OneToNTypeConversion` and `DialectConversion` to replace the
current implementation that uses `GreedyPatternRewriteDriver`.
- Introduce other vector unrolling patterns to cancel out the
`vector.insert_strided_slice` and `vector.extract_strided_slice` ops and
fully legalize the vector types in the function body.
- Handle `func::CallOp` and declarations.
- Restructure the code in `SPIRVConversion.cpp`.
- Create test passes for testing sets of patterns in isolation.
- Optimize the way original shape is splitted into target shapes, e.g.
`vector<5xi32>` can be splitted into `vector<4xi32>` and
`vector<1xi32>`.

---------

Co-authored-by: Jakub Kuderski <[email protected]>

Author: obtuseangleAZ

mlir/include/mlir/Conversion/Passes.td

@@ -40,7 +40,15 @@ def ConvertToSPIRVPass : Pass<"convert-to-spirv"> {
   let description = [{
     This is a generic pass to convert to SPIR-V.
   }];
-  let dependentDialects = ["spirv::SPIRVDialect"];
+  let dependentDialects = [
+    "spirv::SPIRVDialect",
+    "vector::VectorDialect",
+  ];
+  let options = [
+    Option<"runSignatureConversion", "run-signature-conversion", "bool",
+    /*default=*/"true",
+    "Run function signature conversion to convert vector types">
+  ];
 }
 
 //===----------------------------------------------------------------------===//

mlir/include/mlir/Dialect/SPIRV/Transforms/SPIRVConversion.h

@@ -17,7 +17,9 @@
 #include "mlir/Dialect/SPIRV/IR/SPIRVOps.h"
 #include "mlir/Dialect/SPIRV/IR/SPIRVTypes.h"
 #include "mlir/Dialect/SPIRV/IR/TargetAndABI.h"
+#include "mlir/Dialect/Vector/Transforms/VectorRewritePatterns.h"
 #include "mlir/Transforms/DialectConversion.h"
+#include "mlir/Transforms/OneToNTypeConversion.h"
 #include "llvm/ADT/SmallSet.h"
 
 namespace mlir {
@@ -134,6 +136,10 @@ class SPIRVConversionTarget : public ConversionTarget {
 void populateBuiltinFuncToSPIRVPatterns(SPIRVTypeConverter &typeConverter,
                                         RewritePatternSet &patterns);
 
+void populateFuncOpVectorRewritePatterns(RewritePatternSet &patterns);
+
+void populateReturnOpVectorRewritePatterns(RewritePatternSet &patterns);
+
 namespace spirv {
 class AccessChainOp;
 

mlir/lib/Conversion/ConvertToSPIRV/ConvertToSPIRVPass.cpp

@@ -39,18 +39,31 @@ namespace {
 /// A pass to perform the SPIR-V conversion.
 struct ConvertToSPIRVPass final
     : impl::ConvertToSPIRVPassBase<ConvertToSPIRVPass> {
+  using ConvertToSPIRVPassBase::ConvertToSPIRVPassBase;
 
   void runOnOperation() override {
     MLIRContext *context = &getContext();
     Operation *op = getOperation();
 
+    if (runSignatureConversion) {
+      // Unroll vectors in function signatures to native vector size.
+      RewritePatternSet patterns(context);
+      populateFuncOpVectorRewritePatterns(patterns);
+      populateReturnOpVectorRewritePatterns(patterns);
+      GreedyRewriteConfig config;
+      config.strictMode = GreedyRewriteStrictness::ExistingOps;
+      if (failed(applyPatternsAndFoldGreedily(op, std::move(patterns), config)))
+        return signalPassFailure();
+    }
+
     spirv::TargetEnvAttr targetAttr = spirv::lookupTargetEnvOrDefault(op);
+    std::unique_ptr<ConversionTarget> target =
+        SPIRVConversionTarget::get(targetAttr);
     SPIRVTypeConverter typeConverter(targetAttr);
-
     RewritePatternSet patterns(context);
     ScfToSPIRVContext scfToSPIRVContext;
 
-    // Populate patterns.
+    // Populate patterns for each dialect.
     arith::populateCeilFloorDivExpandOpsPatterns(patterns);
     arith::populateArithToSPIRVPatterns(typeConverter, patterns);
     populateBuiltinFuncToSPIRVPatterns(typeConverter, patterns);
@@ -60,9 +73,6 @@ struct ConvertToSPIRVPass final
     populateSCFToSPIRVPatterns(typeConverter, scfToSPIRVContext, patterns);
     ub::populateUBToSPIRVConversionPatterns(typeConverter, patterns);
 
-    std::unique_ptr<ConversionTarget> target =
-        SPIRVConversionTarget::get(targetAttr);
-
     if (failed(applyPartialConversion(op, *target, std::move(patterns))))
       return signalPassFailure();
   }

mlir/lib/Dialect/SPIRV/Transforms/CMakeLists.txt

@@ -16,9 +16,15 @@ add_mlir_dialect_library(MLIRSPIRVConversion
   ${MLIR_MAIN_INCLUDE_DIR}/mlir/Dialect/SPIRV
 
   LINK_LIBS PUBLIC
+  MLIRArithDialect
+  MLIRDialectUtils
   MLIRFuncDialect
+  MLIRIR
   MLIRSPIRVDialect
+  MLIRSupport
   MLIRTransformUtils
+  MLIRVectorDialect
+  MLIRVectorTransforms
 )
 
 add_mlir_dialect_library(MLIRSPIRVTransforms