Add a new bit that ImmLeaf's can opt into, which allows them to duck out of

the generated FastISel.  X86 doesn't need to generate code to match ADD16ri8 
since ADD16ri will do just fine.  This is a small codesize win in the generated
instruction selector.

llvm-svn: 129692

1 files changed, 10 insertions, 2 deletions

diff --git a/llvm/utils/TableGen/FastISelEmitter.cpp b/llvm/utils/TableGen/FastISelEmitter.cpp
index ce821765a2c..e3d47aa49a0 100644
--- a/llvm/utils/TableGen/FastISelEmitter.cpp
+++ b/llvm/utils/TableGen/FastISelEmitter.cpp
@@ -190,14 +190,22 @@ struct OperandsSignature {
       if (!Op->isLeaf() && Op->getOperator()->getName() == "imm") {
         unsigned PredNo = 0;
         if (!Op->getPredicateFns().empty()) {
+          TreePredicateFn PredFn = Op->getPredicateFns()[0];
           // If there is more than one predicate weighing in on this operand
           // then we don't handle it.  This doesn't typically happen for
           // immediates anyway.
           if (Op->getPredicateFns().size() > 1 ||
-              !Op->getPredicateFns()[0].isImmediatePattern())
+              !PredFn.isImmediatePattern())
+            return false;
+          // Ignore any instruction with 'FastIselShouldIgnore', these are
+          // not needed and just bloat the fast instruction selector.  For
+          // example, X86 doesn't need to generate code to match ADD16ri8 since
+          // ADD16ri will do just fine.
+          Record *Rec = PredFn.getOrigPatFragRecord()->getRecord();
+          if (Rec->getValueAsBit("FastIselShouldIgnore"))
             return false;
         
-          PredNo = ImmediatePredicates.getIDFor(Op->getPredicateFns()[0])+1;
+          PredNo = ImmediatePredicates.getIDFor(PredFn)+1;
         }
         
         // Handle unmatched immediate sizes here.