TableGen: Add !dag function for construction

This allows constructing DAG nodes with programmatically determined
names, and can simplify constructing DAG nodes in other cases as
well.

Also, add documentation and some very simple tests for the already
existing !con.

Change-Id: Ida61cd82e99752548d7109ce8da34d29da56a5f7

Differential revision: https://reviews.llvm.org/D44110

llvm-svn: 327492

1 files changed, 39 insertions, 0 deletions

diff --git a/llvm/lib/TableGen/TGParser.cpp b/llvm/lib/TableGen/TGParser.cpp
index 5d87bfdf19d..629320975a6 100644
--- a/llvm/lib/TableGen/TGParser.cpp
+++ b/llvm/lib/TableGen/TGParser.cpp
@@ -1159,6 +1159,7 @@ Init *TGParser::ParseOperation(Record *CurRec, RecTy *ItemType) {
                ->Fold(CurRec, CurMultiClass);
   }
 
+  case tgtok::XDag:
   case tgtok::XIf:
   case tgtok::XSubst: {  // Value ::= !ternop '(' Value ',' Value ',' Value ')'
     TernOpInit::TernaryOp Code;
@@ -1168,6 +1169,11 @@ Init *TGParser::ParseOperation(Record *CurRec, RecTy *ItemType) {
     Lex.Lex();  // eat the operation
     switch (LexCode) {
     default: llvm_unreachable("Unhandled code!");
+    case tgtok::XDag:
+      Code = TernOpInit::DAG;
+      Type = DagRecTy::get();
+      ItemType = nullptr;
+      break;
     case tgtok::XIf:
       Code = TernOpInit::IF;
       break;
@@ -1190,6 +1196,7 @@ Init *TGParser::ParseOperation(Record *CurRec, RecTy *ItemType) {
     }
     Lex.Lex();  // eat the ','
 
+    SMLoc MHSLoc = Lex.getLoc();
     Init *MHS = ParseValue(CurRec, ItemType);
     if (!MHS)
       return nullptr;
@@ -1200,6 +1207,7 @@ Init *TGParser::ParseOperation(Record *CurRec, RecTy *ItemType) {
     }
     Lex.Lex();  // eat the ','
 
+    SMLoc RHSLoc = Lex.getLoc();
     Init *RHS = ParseValue(CurRec, ItemType);
     if (!RHS)
       return nullptr;
@@ -1212,6 +1220,36 @@ Init *TGParser::ParseOperation(Record *CurRec, RecTy *ItemType) {
 
     switch (LexCode) {
     default: llvm_unreachable("Unhandled code!");
+    case tgtok::XDag: {
+      TypedInit *MHSt = dyn_cast<TypedInit>(MHS);
+      if (!MHSt && !isa<UnsetInit>(MHS)) {
+        Error(MHSLoc, "could not determine type of the child list in !dag");
+        return nullptr;
+      }
+      if (MHSt && !isa<ListRecTy>(MHSt->getType())) {
+        Error(MHSLoc, Twine("expected list of children, got type '") +
+                          MHSt->getType()->getAsString() + "'");
+        return nullptr;
+      }
+
+      TypedInit *RHSt = dyn_cast<TypedInit>(RHS);
+      if (!RHSt && !isa<UnsetInit>(RHS)) {
+        Error(RHSLoc, "could not determine type of the name list in !dag");
+        return nullptr;
+      }
+      if (RHSt && StringRecTy::get()->getListTy() != RHSt->getType()) {
+        Error(RHSLoc, Twine("expected list<string>, got type '") +
+                          RHSt->getType()->getAsString() + "'");
+        return nullptr;
+      }
+
+      if (!MHSt && !RHSt) {
+        Error(MHSLoc,
+              "cannot have both unset children and unset names in !dag");
+        return nullptr;
+      }
+      break;
+    }
     case tgtok::XIf: {
       RecTy *MHSTy = nullptr;
       RecTy *RHSTy = nullptr;
@@ -1728,6 +1766,7 @@ Init *TGParser::ParseSimpleValue(Record *CurRec, RecTy *ItemType,
   case tgtok::XCast:  // Value ::= !unop '(' Value ')'
   case tgtok::XIsA:
   case tgtok::XConcat:
+  case tgtok::XDag:
   case tgtok::XADD:
   case tgtok::XAND:
   case tgtok::XOR: