[TableGen] Eliminate the dependency on SDNode definition orderusers/atrosinenko/tablegen-fix-operandwithdefaultops

Fix CodeGenDAGPatterns::ParseDefaultOperands() not to depend on the
first SDNode defined being usable as an output pattern operator.

Presently, each `OperandWithDefaultOps` record is processed by
constructing an instance of TreePattern from its `DefaultOps` argument
that has the form `(ops ...)`. Nevertheless the result of processing
the root operator of that DAG is not inspected by `ParseDefaultOperands()`
function itself, that operator has to be parseable by the underlying
`TreePattern::ParseTreePattern()` function. For that reason, a temporary
DAG is created by replacing the root operator of `DefaultOps` argument
from `ops` to the first SDNode defined, which is usually `def imm : ...`
defined in `TargetSelectionDAG.td` file.

This results in misleading errors being reported when defining new
`SDNode` types, if the new definition happens to be added before the
`def imm : ...` line. The error is reported by several test cases
executed by `check-llvm` target, as well as if one of the targets
being built inherits its operand type from `OperandWithDefaultOps`:

    OptionalIntOperand: ../llvm/test/TableGen/DAGDefaultOps.td:28:5: error: In OptionalIntOperand: Cannot use 'unexpected_node' in an output pattern!
    def OptionalIntOperand: OperandWithDefaultOps<i32, (ops (i32 0))>;

This commit implements a dedicated constructor of `TreePattern` to be
used if the caller does not care about the particular root operator of
the pattern being processed.

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/utils/TableGen/Common/CodeGenDAGPatterns.h b/llvm/utils/TableGen/Common/CodeGenDAGPatterns.h
index aa9a0a442424..f69a606a8406 100644
--- a/llvm/utils/TableGen/Common/CodeGenDAGPatterns.h
+++ b/llvm/utils/TableGen/Common/CodeGenDAGPatterns.h
@@ -925,6 +925,9 @@ public:
               CodeGenDAGPatterns &ise);
   TreePattern(const Record *TheRec, const DagInit *Pat, bool isInput,
               CodeGenDAGPatterns &ise);
+  TreePattern(const Record *TheRec, ArrayRef<const Init *> Args,
+              ArrayRef<const StringInit *> ArgNames, bool isInput,
+              CodeGenDAGPatterns &ise);
   TreePattern(const Record *TheRec, TreePatternNodePtr Pat, bool isInput,
               CodeGenDAGPatterns &ise);
 
@@ -989,6 +992,9 @@ public:
 
 private:
   TreePatternNodePtr ParseTreePattern(const Init *DI, StringRef OpName);
+  TreePatternNodePtr
+  ParseRootlessTreePattern(ArrayRef<const Init *> Args,
+                           ArrayRef<const StringInit *> ArgNames);
   void ComputeNamedNodes();
   void ComputeNamedNodes(TreePatternNode &N);
 };