[mlir] Use empty() calls where possible.

These are based on findings from the ClangTidy
readability-container-size-empty check.

Author: akuegel

mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp

@@ -82,7 +82,7 @@ parseOperandList(OpAsmParser &parser, StringRef keyword,
 static void printOperandList(Operation::operand_range operands,
                              StringRef listName, OpAsmPrinter &printer) {
 
-  if (operands.size() > 0) {
+  if (!operands.empty()) {
     printer << " " << listName << "(";
     llvm::interleaveComma(operands, printer, [&](Value op) {
       printer << op << ": " << op.getType();
@@ -692,7 +692,7 @@ static LogicalResult verify(acc::DataOp dataOp) {
   // 2.6.5. Data Construct restriction
   // At least one copy, copyin, copyout, create, no_create, present, deviceptr,
   // attach, or default clause must appear on a data construct.
-  if (dataOp.getOperands().size() == 0 && !dataOp.defaultAttr())
+  if (dataOp.getOperands().empty() && !dataOp.defaultAttr())
     return dataOp.emitError("at least one operand or the default attribute "
                             "must appear on the data operation");
   return success();
@@ -838,8 +838,7 @@ static LogicalResult verify(acc::ShutdownOp op) {
 
 static LogicalResult verify(acc::UpdateOp updateOp) {
   // At least one of host or device should have a value.
-  if (updateOp.hostOperands().size() == 0 &&
-      updateOp.deviceOperands().size() == 0)
+  if (updateOp.hostOperands().empty() && updateOp.deviceOperands().empty())
     return updateOp.emitError("at least one value must be present in"
                               " hostOperands or deviceOperands");
 
@@ -851,10 +850,10 @@ static LogicalResult verify(acc::UpdateOp updateOp) {
 
   // The wait attribute represent the wait clause without values. Therefore the
   // attribute and operands cannot appear at the same time.
-  if (updateOp.waitOperands().size() > 0 && updateOp.wait())
+  if (!updateOp.waitOperands().empty() && updateOp.wait())
     return updateOp.emitError("wait attribute cannot appear with waitOperands");
 
-  if (updateOp.waitDevnum() && updateOp.waitOperands().size() == 0)
+  if (updateOp.waitDevnum() && updateOp.waitOperands().empty())
     return updateOp.emitError("wait_devnum cannot appear without waitOperands");
 
   return success();