make IRBuilder zap "X|0" and "X&-1" when building IR, this happens

during bitfield codegen and slows down -O0 compile times by making
useless IR.  rdar://7362516

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86006 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Support/IRBuilder.h b/include/llvm/Support/IRBuilder.h
index 8f26cea34cf7725d34d794a5423ac3694e4fdb6e..4652e8fb941706b9cd8402387ce7a6f04964d643 100644 (file)
--- a/include/llvm/Support/IRBuilder.h
+++ b/include/llvm/Support/IRBuilder.h
@@ -390,15 +390,21 @@ public:
     return Insert(BinaryOperator::CreateAShr(LHS, RHS), Name);
   }
   Value *CreateAnd(Value *LHS, Value *RHS, const Twine &Name = "") {
-    if (Constant *LC = dyn_cast<Constant>(LHS))
-      if (Constant *RC = dyn_cast<Constant>(RHS))
+    if (Constant *RC = dyn_cast<Constant>(RHS)) {
+      if (isa<ConstantInt>(RC) && cast<ConstantInt>(RC)->isAllOnesValue())
+        return LHS;  // LHS & -1 -> LHS
+      if (Constant *LC = dyn_cast<Constant>(LHS))
         return Folder.CreateAnd(LC, RC);
+    }
     return Insert(BinaryOperator::CreateAnd(LHS, RHS), Name);
   }
   Value *CreateOr(Value *LHS, Value *RHS, const Twine &Name = "") {
-    if (Constant *LC = dyn_cast<Constant>(LHS))
-      if (Constant *RC = dyn_cast<Constant>(RHS))
+    if (Constant *RC = dyn_cast<Constant>(RHS)) {
+      if (RC->isNullValue())
+        return LHS;  // LHS | 0 -> LHS
+      if (Constant *LC = dyn_cast<Constant>(LHS))
         return Folder.CreateOr(LC, RC);
+    }
     return Insert(BinaryOperator::CreateOr(LHS, RHS), Name);
   }
   Value *CreateXor(Value *LHS, Value *RHS, const Twine &Name = "") {