Remove a top-level "using namespace" from TargetTransformInfoImpl.h

Move it into the implementation of the function that needs it.

Avoids polluting the namespace of all files including the header.

Author: labath

llvm/include/llvm/Analysis/TargetTransformInfoImpl.h

@@ -24,8 +24,6 @@
 #include "llvm/IR/PatternMatch.h"
 #include <utility>
 
-using namespace llvm::PatternMatch;
-
 namespace llvm {
 
 class Function;
@@ -960,6 +958,8 @@ class TargetTransformInfoImplCRTPBase : public TargetTransformInfoImplBase {
 
   InstructionCost getUserCost(const User *U, ArrayRef<const Value *> Operands,
                               TTI::TargetCostKind CostKind) {
+    using namespace llvm::PatternMatch;
+
     auto *TargetTTI = static_cast<T *>(this);
     // Handle non-intrinsic calls, invokes, and callbr.
     // FIXME: Unlikely to be true for anything but CodeSize.