[MLIR] Add C API for navigating up the IR tree

[GeorgeLyon]

Add context accessor on operation

[mehdi_amini]

Can you add tests for all of the APIs added?

[GeorgeLyon]

Add Tests

[GeorgeLyon]

Missed a few

[GeorgeLyon]

Missed one

[GeorgeLyon]

Rebase

mlir/include/mlir-c/IR.h

 /// Checks whether the underlying operation is null.
 static inline bool mlirOperationIsNull(MlirOperation op) { return !op.ptr; }
 
 /// Checks whether two operation handles point to the same operation. This does
 /// not perform deep comparison.
 MLIR_CAPI_EXPORTED bool mlirOperationEqual(MlirOperation op,
                                            MlirOperation other);
 
+/// Gets the context this operation is associated with
+MLIR_CAPI_EXPORTED MlirContext mlirOperationGetContext(MlirOperation op);
+
 /// Gets the name of the operation as an identifier.
 MLIR_CAPI_EXPORTED MlirIdentifier mlirOperationGetName(MlirOperation op);
 
 /// Gets the block that owns this operation, returning null if the operation is
 /// not owned.
 MLIR_CAPI_EXPORTED MlirBlock mlirOperationGetBlock(MlirOperation op);
 
 /// Gets the operation that owns this operation, returning null if the operation

 
 /// Checks whether a block is null.
 static inline bool mlirBlockIsNull(MlirBlock block) { return !block.ptr; }
 
 /// Checks whether two blocks handles point to the same block. This does not
 /// perform deep comparison.
 MLIR_CAPI_EXPORTED bool mlirBlockEqual(MlirBlock block, MlirBlock other);
 
+/// Returns the closest surrounding operation that contains this block.
+MLIR_CAPI_EXPORTED MlirOperation mlirBlockGetParentOperation(MlirBlock);
+
 /// Returns the block immediately following the given block in its parent
 /// region.
 MLIR_CAPI_EXPORTED MlirBlock mlirBlockGetNextInRegion(MlirBlock block);
 
 /// Returns the first operation in the block.
 MLIR_CAPI_EXPORTED MlirOperation mlirBlockGetFirstOperation(MlirBlock block);
 
 /// Returns the terminator operation in the block or null if no terminator.

mlir/lib/CAPI/IR/IR.cpp

 }
 
 void mlirOperationDestroy(MlirOperation op) { unwrap(op)->erase(); }
 
 bool mlirOperationEqual(MlirOperation op, MlirOperation other) {
   return unwrap(op) == unwrap(other);
 }
 
+MlirContext mlirOperationGetContext(MlirOperation op) {
+  return wrap(unwrap(op)->getContext());
+}
+
 MlirIdentifier mlirOperationGetName(MlirOperation op) {
   return wrap(unwrap(op)->getName().getIdentifier());
 }
 
 MlirBlock mlirOperationGetBlock(MlirOperation op) {
   return wrap(unwrap(op)->getBlock());
 }
 
for (intptr_t i = 0; i < nArgs; ++i)
     b->addArgument(unwrap(args[i]));
   return wrap(b);
 }
 
 bool mlirBlockEqual(MlirBlock block, MlirBlock other) {
   return unwrap(block) == unwrap(other);
 }
 
+MlirOperation mlirBlockGetParentOperation(MlirBlock block) {
+  return wrap(unwrap(block)->getParentOp());
+}
+
 MlirBlock mlirBlockGetNextInRegion(MlirBlock block) {
   return wrap(unwrap(block)->getNextNode());
 }
 
 MlirOperation mlirBlockGetFirstOperation(MlirBlock block) {
   Block *cppBlock = unwrap(block);
   if (cppBlock->empty())
     return wrap(static_cast<Operation *>(nullptr));

mlir/test/CAPI/ir.c

if (stdNs.length != alsoStdNs.length ||
     return 5;
 
   fprintf(stderr, "@registration\n");
   // CHECK-LABEL: @registration
 
   return 0;
 }
 
+/// Tests backreference APIs
+static int testBackreferences() {
+  fprintf(stderr, "@test_backreferences\n");
+
+  MlirContext ctx = mlirContextCreate();
+  mlirContextSetAllowUnregisteredDialects(ctx, true);
+  MlirLocation loc = mlirLocationUnknownGet(ctx);
+
+  MlirOperationState opState = mlirOperationStateGet(mlirStringRefCreateFromCString("invalid.op"), loc);
+  MlirRegion region = mlirRegionCreate();
+  MlirBlock block = mlirBlockCreate(0, NULL);
+  mlirRegionAppendOwnedBlock(region, block);
+  mlirOperationStateAddOwnedRegions(&opState, 1, &region);
+  MlirOperation op = mlirOperationCreate(&opState);
+
+  if (!mlirContextEqual(ctx, mlirOperationGetContext(op))) {
+    fprintf(stderr, "ERROR: Getting context from operation failed\n");
+    return 1;
+  }
+  if (!mlirOperationEqual(op, mlirBlockGetParentOperation(block))) {
+    fprintf(stderr, "ERROR: Getting parent operation from block failed\n");
+    return 2;
+  }
+  
+  mlirOperationDestroy(op);
+  mlirContextDestroy(ctx);
+
+  // CHECK-LABEL: @test_backreferences
+  return 0;
+}
+
 // Wraps a diagnostic into additional text we can match against.
 MlirLogicalResult errorHandler(MlirDiagnostic diagnostic, void *userData) {
   fprintf(stderr, "processing diagnostic (userData: %ld) <<\n", (long)userData);
   mlirDiagnosticPrint(diagnostic, printToStderr, NULL);
   fprintf(stderr, "\n");
   MlirLocation loc = mlirDiagnosticGetLocation(diagnostic);
   mlirLocationPrint(loc, printToStderr, NULL);
   assert(mlirDiagnosticGetNumNotes(diagnostic) == 0);
int main() {
   if (printAffineExpr(ctx))
     return 6;
   if (affineMapFromExprs(ctx))
     return 7;
   if (printIntegerSet(ctx))
     return 8;
   if (registerOnlyStd())
     return 9;
+  if (testBackreferences())
+    return 10;
 
   mlirContextDestroy(ctx);
 
   testDiagnostics();
   return 0;
 }