[NFC] Fix unused warning.

Differential Revision: https://reviews.llvm.org/D100449
diff --git a/llvm/lib/Target/X86/X86TileConfig.cpp b/llvm/lib/Target/X86/X86TileConfig.cpp
index 44b7418..d5e6e33 100644
--- a/llvm/lib/Target/X86/X86TileConfig.cpp
+++ b/llvm/lib/Target/X86/X86TileConfig.cpp
@@ -151,6 +151,7 @@
       // 55     tile7.rows Tile 7 rows.
       // 56-63  reserved, must be zero
       int ImmCount = 0;
+      (void)ImmCount;
       int Offset = IsRow ? 48 + I : 16 + I * 2;
       for (auto &DefMI : MRI.def_instructions(R)) {
         MachineBasicBlock &MBB = *DefMI.getParent();