[llvm-exegesis][NFC] Add missing header guard + cosmetics.

Reviewers: gchatelet

Reviewed By: gchatelet

Subscribers: tschuett, llvm-commits

Differential Revision: https://reviews.llvm.org/D54252

llvm-svn: 346400
diff --git a/llvm/tools/llvm-exegesis/lib/SnippetGenerator.cpp b/llvm/tools/llvm-exegesis/lib/SnippetGenerator.cpp
index eb6a857..88ba315 100644
--- a/llvm/tools/llvm-exegesis/lib/SnippetGenerator.cpp
+++ b/llvm/tools/llvm-exegesis/lib/SnippetGenerator.cpp
@@ -91,7 +91,7 @@
       if (Op.isUse()) {
         const unsigned Reg = GetOpReg(Op);
         if (Reg > 0 && !DefinedRegs.test(Reg)) {
-          RIV.push_back(RegisterValue{Reg, llvm::APInt()});
+          RIV.push_back(RegisterValue::zero(Reg));
           DefinedRegs.set(Reg);
         }
       }