[TableGen][SelectionDAG] Remove the `implicit` DAG node (#115295)

The node was introduced in 59c39dc1 and was intended to allow writing
patterns like this:
`[(set AL, (mul AL, GR8:$src1)), (implicit EFLAGS)]`

However, it does not introduce new functionality because the same
pattern can be equivalently expressed as:
`[(set AL, EFLAGS, (mul AL, GR8:$src1))]`

The latter form is also more flexible as it allows reordering output
operands.

In most places uses of `implicit` were redundant -- removing them didn't
change anything in the generated DAG tables. The only three cases where
it did have effect are in X86InstrArithmetic.td and X86InstrSystem.td --
those were rewritten to use `set` node.

Removing `implicit` from some patterns made them importable by GISel,
hence the change in a test.

1 files changed, 2 insertions, 18 deletions

diff --git a/llvm/utils/TableGen/Common/CodeGenDAGPatterns.cpp b/llvm/utils/TableGen/Common/CodeGenDAGPatterns.cpp
index f17c62d..c8186d6 100644
--- a/llvm/utils/TableGen/Common/CodeGenDAGPatterns.cpp
+++ b/llvm/utils/TableGen/Common/CodeGenDAGPatterns.cpp
@@ -1838,7 +1838,7 @@ MVT::SimpleValueType SDNodeInfo::getKnownType(unsigned ResNo) const {
 
 static unsigned GetNumNodeResults(const Record *Operator,
                                   CodeGenDAGPatterns &CDP) {
-  if (Operator->getName() == "set" || Operator->getName() == "implicit")
+  if (Operator->getName() == "set")
     return 0; // All return nothing.
 
   if (Operator->isSubClassOf("Intrinsic"))
@@ -2945,8 +2945,7 @@ TreePatternNodePtr TreePattern::ParseTreePattern(const Init *TheInit,
       !Operator->isSubClassOf("Instruction") &&
       !Operator->isSubClassOf("SDNodeXForm") &&
       !Operator->isSubClassOf("Intrinsic") &&
-      !Operator->isSubClassOf("ComplexPattern") &&
-      Operator->getName() != "set" && Operator->getName() != "implicit")
+      !Operator->isSubClassOf("ComplexPattern") && Operator->getName() != "set")
     error("Unrecognized node '" + Operator->getName() + "'!");
 
   //  Check to see if this is something that is illegal in an input pattern.
@@ -3456,21 +3455,6 @@ void CodeGenDAGPatterns::FindPatternInputsAndOutputs(
     return;
   }
 
-  if (Pat->getOperator()->getName() == "implicit") {
-    for (unsigned i = 0, e = Pat->getNumChildren(); i != e; ++i) {
-      TreePatternNode &Dest = Pat->getChild(i);
-      if (!Dest.isLeaf())
-        I.error("implicitly defined value should be a register!");
-
-      const DefInit *Val = dyn_cast<DefInit>(Dest.getLeafValue());
-      if (!Val || !Val->getDef()->isSubClassOf("Register"))
-        I.error("implicitly defined value should be a register!");
-      if (Val)
-        InstImpResults.push_back(Val->getDef());
-    }
-    return;
-  }
-
   if (Pat->getOperator()->getName() != "set") {
     // If this is not a set, verify that the children nodes are not void typed,
     // and recurse.