TableGen/DAGPatterns: Allow bit constants in addition to int constants

[nhaehnle]

Summary

Implicit casting is a simple quality of life improvement.

Change-Id: I3d2b31b8b8f12cbb1e84f691e359fa713a9c4b42

[tra]

LGTM in general.
It would be good to add a test that we can use bits w/o explicit casting now.

[nhaehnle]

I agree on the test case, unfortunately it requires a lot of setup to make the backend do anything useful at all.

[tra]

In D47432#1116186, @nhaehnle wrote:

I agree on the test case, unfortunately it requires a lot of setup to make the backend do anything useful at all.

Sorry, I've missed that it's a back-end change. LGTM.

utils/TableGen/CodeGenDAGPatterns.cpp

if (isa<UnsetInit>(TheInit)) {
     if (OpName.empty())
       error("'?' argument requires a name to match with operand list");
     TreePatternNode *Res = new TreePatternNode(TheInit, 1);
     Args.push_back(OpName);
     Res->setName(OpName);
     return Res;
   }
 
-  if (IntInit *II = dyn_cast<IntInit>(TheInit)) {
+  if (isa<IntInit>(TheInit) || isa<BitInit>(TheInit)) {
     if (!OpName.empty())
-      error("Constant int argument should not have a name!");
-    return new TreePatternNode(II, 1);
+      error("Constant int or bit argument should not have a name!");
+    if (isa<BitInit>(TheInit))
+      TheInit = TheInit->convertInitializerTo(IntRecTy::get());
+    return new TreePatternNode(TheInit, 1);
   }
 
   if (BitsInit *BI = dyn_cast<BitsInit>(TheInit)) {
     // Turn this into an IntInit.
     Init *II = BI->convertInitializerTo(IntRecTy::get());
     if (!II || !isa<IntInit>(II))
       error("Bits value must be constants!");
     return ParseTreePattern(II, OpName);