[mlir][Transforms] Dialect Conversion: Add replaceOpWithMultiple (#115816)

This commit adds a new function
`ConversionPatternRewriter::replaceOpWithMultiple`. This function is
similar to `replaceOp`, but it accepts multiple `ValueRange`
replacements, one per op result.

Note: This function is not an overload of `replaceOp` because of
ambiguous overload resolution that would make the API difficult to use.

This commit aligns "block signature conversions" with "op replacements":
both support 1:N replacements now. Due to incomplete 1:N support in the
dialect conversion driver, an argument materialization is inserted when
an SSA value is replaced with multiple values; same as block signature
conversions already work around the problem. These argument
materializations are going to be removed in a subsequent commit that
adds full 1:N support. The purpose of this PR is to add missing features
gradually in small increments.

This commit also updates two MLIR transformations that have their custom
workarounds around missing 1:N support. These can already start using
`replaceOpWithMultiple`.

Co-authored-by: Markus Böck <markus.boeck02@gmail.com>

mlir/lib/Dialect/SparseTensor/Transforms/SparseTensorCodegen.cpp

@@ -600,8 +600,8 @@ public:
     flattenOperands(adaptor.getOperands(), flattened);
     auto newCall = rewriter.create<func::CallOp>(loc, op.getCallee(),
                                                  finalRetTy, flattened);
-    // (2) Create cast operation for sparse tensor returns.
-    SmallVector<Value> castedRet;
+    // (2) Gather sparse tensor returns.
+    SmallVector<SmallVector<Value>> packedResultVals;
     // Tracks the offset of current return value (of the original call)
     // relative to the new call (after sparse tensor flattening);
     unsigned retOffset = 0;
@@ -618,21 +618,22 @@ public:
       assert(!sparseFlat.empty());
       if (sparseFlat.size() > 1) {
         auto flatSize = sparseFlat.size();
-        ValueRange fields(iterator_range<ResultRange::iterator>(
-            newCall.result_begin() + retOffset,
-            newCall.result_begin() + retOffset + flatSize));
-        castedRet.push_back(genTuple(rewriter, loc, retType, fields));
+        packedResultVals.emplace_back();
+        llvm::append_range(packedResultVals.back(),
+                           newCall.getResults().slice(retOffset, flatSize));
         retOffset += flatSize;
       } else {
         // If this is an 1:1 conversion, no need for casting.
-        castedRet.push_back(newCall.getResult(retOffset));
+        packedResultVals.emplace_back();
+        packedResultVals.back().push_back(newCall.getResult(retOffset));
         retOffset++;
       }
       sparseFlat.clear();
     }
 
-    assert(castedRet.size() == op.getNumResults());
-    rewriter.replaceOp(op, castedRet);
+    assert(packedResultVals.size() == op.getNumResults());
+    rewriter.replaceOpWithMultiple(
+        op, llvm::to_vector_of<ValueRange>(packedResultVals));
     return success();
   }
 };
@@ -776,7 +777,7 @@ public:
       // Reuses specifier.
       fields.push_back(desc.getSpecifier());
       assert(fields.size() == desc.getNumFields());
-      rewriter.replaceOp(op, genTuple(rewriter, loc, resType, fields));
+      rewriter.replaceOpWithMultiple(op, {fields});
       return success();
     }
 
@@ -796,7 +797,7 @@ public:
                       sizeHint, lvlSizesValues, fields);
 
     // Replace operation with resulting memrefs.
-    rewriter.replaceOp(op, genTuple(rewriter, loc, resType, fields));
+    rewriter.replaceOpWithMultiple(op, {fields});
     return success();
   }
 
@@ -837,7 +838,7 @@ public:
                       sizeHint, lvlSizesValues, fields);
 
     // Replace operation with resulting memrefs.
-    rewriter.replaceOp(op, genTuple(rewriter, loc, resType, fields));
+    rewriter.replaceOpWithMultiple(op, {fields});
     return success();
   }
 
@@ -893,7 +894,7 @@ public:
     if (op.getHasInserts())
       genEndInsert(rewriter, op.getLoc(), desc);
     // Replace operation with resulting memrefs.
-    rewriter.replaceOp(op, genTuple(rewriter, op.getLoc(), desc));
+    rewriter.replaceOpWithMultiple(op, {desc.getFields()});
     return success();
   }
 };
@@ -1006,7 +1007,6 @@ public:
     rewriter.create<scf::YieldOp>(loc, insertRet);
 
     rewriter.setInsertionPointAfter(loop);
-    Value result = genTuple(rewriter, loc, dstType, loop->getResults());
     // Deallocate the buffers on exit of the full loop nest.
     Operation *parent = getTop(op);
     rewriter.setInsertionPointAfter(parent);
@@ -1014,7 +1014,7 @@ public:
     rewriter.create<memref::DeallocOp>(loc, filled);
     rewriter.create<memref::DeallocOp>(loc, added);
     // Replace operation with resulting memrefs.
-    rewriter.replaceOp(op, result);
+    rewriter.replaceOpWithMultiple(op, {loop->getResults()});
     return success();
   }
 };
@@ -1041,8 +1041,7 @@ public:
                                     params, /*genCall=*/true);
     SmallVector<Value> ret = insertGen.genCallOrInline(rewriter, loc);
     // Replace operation with resulting memrefs.
-    rewriter.replaceOp(op,
-                       genTuple(rewriter, loc, op.getDest().getType(), ret));
+    rewriter.replaceOpWithMultiple(op, {ret});
     return success();
   }
 };
@@ -1215,8 +1214,7 @@ public:
           return true;
         });
 
-    rewriter.replaceOp(
-        op, genTuple(rewriter, loc, op.getResult().getType(), fields));
+    rewriter.replaceOpWithMultiple(op, {fields});
     return success();
   }
 };
@@ -1271,8 +1269,7 @@ public:
     // NOTE: we can not generate tuples directly from descriptor here, as the
     // descriptor is holding the original type, yet we want the slice type
     // here (they shared every memref but with an updated specifier).
-    rewriter.replaceOp(op, genTuple(rewriter, loc, op.getResult().getType(),
-                                    desc.getFields()));
+    rewriter.replaceOpWithMultiple(op, {desc.getFields()});
     return success();
   }
 };
@@ -1403,7 +1400,7 @@ struct SparseAssembleOpConverter : public OpConversionPattern<AssembleOp> {
     }
     desc.setValMemSize(rewriter, loc, memSize);
 
-    rewriter.replaceOp(op, genTuple(rewriter, loc, desc));
+    rewriter.replaceOpWithMultiple(op, {desc.getFields()});
     return success();
   }
 };
@@ -1577,7 +1574,7 @@ struct SparseNewConverter : public OpConversionPattern<NewOp> {
                    EmitCInterface::Off);
 
     // Replace operation with resulting memrefs.
-    rewriter.replaceOp(op, genTuple(rewriter, loc, dstTp, fields));
+    rewriter.replaceOpWithMultiple(op, {fields});
     return success();
   }
 };