[WebAssembly] Expand BUILD_PAIR nodes

Reviewers: aheejin

Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, sunfish

Differential Revision: https://reviews.llvm.org/D57276

llvm-svn: 352442
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
index 7186d29..1a8b598 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyISelLowering.cpp
@@ -225,6 +225,9 @@
     }
   }
 
+  // Don't do anything clever with build_pairs
+  setOperationAction(ISD::BUILD_PAIR, MVT::i64, Expand);
+
   // Trap lowers to wasm unreachable
   setOperationAction(ISD::TRAP, MVT::Other, Legal);