[AMDGPU] Make __GCC_DESTRUCTIVE_SIZE 128 on AMDGPU

Summary:
The cache line size on AMDGPU varies between 64 and 128 (The lowest L2
cache also goes to 256 on some architectures.) This macro is intended to
present a size that will not cause destructive interference, so we
choose the larger of those values.

Author: jhuber6

clang/lib/Basic/Targets/AMDGPU.h

@@ -462,6 +462,10 @@ class LLVM_LIBRARY_VISIBILITY AMDGPUTargetInfo final : public TargetInfo {
   }
 
   bool hasHIPImageSupport() const override { return HasImage; }
+
+  std::pair<unsigned, unsigned> hardwareInterferenceSizes() const override {
+    return std::make_pair(128, 128);
+  }
 };
 
 } // namespace targets