WebAssembly: add a generic CPU

Summary: WebAssemblySubtarget.cpp expects a default 'generic' CPU to exist, and this seems to be prevalent with other targets. It makes sense to have something between MVP and bleeding-edge, even though for now it's the same as MVP. This removes a warning that's currently generated.

Subscribers: jfb, llvm-commits, sunfish

Differential Revision: http://reviews.llvm.org/D11546

llvm-svn: 243345
diff --git a/llvm/lib/Target/WebAssembly/WebAssembly.td b/llvm/lib/Target/WebAssembly/WebAssembly.td
index a123bf6..53dd929 100644
--- a/llvm/lib/Target/WebAssembly/WebAssembly.td
+++ b/llvm/lib/Target/WebAssembly/WebAssembly.td
@@ -50,6 +50,9 @@
 // Minimal Viable Product.
 def : ProcessorModel<"mvp", NoSchedModel, []>;
 
+// Generic processor: latest stable version.
+def : ProcessorModel<"generic", NoSchedModel, []>;
+
 // Latest and greatest experimental version of WebAssembly. Bugs included!
 def : ProcessorModel<"bleeding-edge", NoSchedModel, [FeatureSIMD128]>;