Emit a redundant check for immediates at root context, e.g. (imm 0).

This allows formation of OpcodeSwitch for top level patterns, in
particular on X86.  This saves about 1K of data space in the x86
table and makes the dispatch much more efficient.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97440 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 1 deletions

diff --git a/utils/TableGen/DAGISelMatcherGen.cpp b/utils/TableGen/DAGISelMatcherGen.cpp
index 95cfa5b..62442d0 100644
--- a/utils/TableGen/DAGISelMatcherGen.cpp
+++ b/utils/TableGen/DAGISelMatcherGen.cpp
@@ -205,8 +205,17 @@ void MatcherGen::EmitLeafMatchCode(const TreePatternNode *N) {
     AddMatcher(new CheckPredicateMatcher(N->getPredicateFns()[i]));
   
   // Direct match against an integer constant.
-  if (IntInit *II = dynamic_cast<IntInit*>(N->getLeafValue()))
+  if (IntInit *II = dynamic_cast<IntInit*>(N->getLeafValue())) {
+    // If this is the root of the dag we're matching, we emit a redundant opcode
+    // check to ensure that this gets folded into the normal top-level
+    // OpcodeSwitch.
+    if (N == Pattern.getSrcPattern()) {
+      const SDNodeInfo &NI = CGP.getSDNodeInfo(CGP.getSDNodeNamed("imm"));
+      AddMatcher(new CheckOpcodeMatcher(NI));
+    }
+
     return AddMatcher(new CheckIntegerMatcher(II->getValue()));
+  }
   
   DefInit *DI = dynamic_cast<DefInit*>(N->getLeafValue());
   if (DI == 0) {