[TableGen][ISel] When factoring ScopeMatcher, if the child of the ScopeMatcher we're working on is also a ScopeMatcher, merge all its children into the one we're working on.

There were several cases in X86 where we were unable to fully factor a ScopeMatcher but created nested ScopeMatchers for some portions of it. Then we created a SwitchType that split it up and further factored it so that we ended up with something like this:

SwitchType
  Scope
    Scope
      Sequence of matchers
      Some other sequence of matchers
    EndScope
    Another sequence of matchers
  EndScope
...Next type

This change turns it into this:

SwitchType
  Scope
    Sequence of matchers
    Some other sequence of matchers
    Another sequence of matchers
  EndScope
...Next type

Several other in-tree targets had similar nested scopes like this. Overall this doesn't save many bytes, but makes the isel output a little more regular.

llvm-svn: 287624

1 files changed, 9 insertions, 2 deletions

diff --git a/llvm/utils/TableGen/DAGISelMatcherOpt.cpp b/llvm/utils/TableGen/DAGISelMatcherOpt.cpp
index 74370c077f8..783b35e745f 100644
--- a/llvm/utils/TableGen/DAGISelMatcherOpt.cpp
+++ b/llvm/utils/TableGen/DAGISelMatcherOpt.cpp
@@ -200,8 +200,15 @@ static void FactorNodes(std::unique_ptr<Matcher> &MatcherPtr) {
     std::unique_ptr<Matcher> Child(Scope->takeChild(i));
     FactorNodes(Child);
     
-    if (Matcher *N = Child.release())
-      OptionsToMatch.push_back(N);
+    if (Child) {
+      // If the child is a ScopeMatcher we can just merge its contents.
+      if (auto *SM = dyn_cast<ScopeMatcher>(Child.get())) {
+        for (unsigned j = 0, e = SM->getNumChildren(); j != e; ++j)
+          OptionsToMatch.push_back(SM->takeChild(j));
+      } else {
+        OptionsToMatch.push_back(Child.release());
+      }
+    }
   }
   
   SmallVector<Matcher*, 32> NewOptionsToMatch;