Remap ssa RealPredicate to llvm RealPredicate

to avoid relying on the discriminant of the former for FFI purposes

compiler/rustc_codegen_llvm/src/builder.rs

@@ -828,6 +828,7 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
     }
 
     fn fcmp(&mut self, op: RealPredicate, lhs: &'ll Value, rhs: &'ll Value) -> &'ll Value {
+        let op = llvm::RealPredicate::from_generic(op);
         unsafe { llvm::LLVMBuildFCmp(self.llbuilder, op as c_uint, lhs, rhs, UNNAMED) }
     }