[WebAssembly][NFC] Fix signed/unsigned comparison warning

llvm-svn: 344459
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
index af5c035..b0fd6ca 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyInstrSIMD.td
@@ -30,7 +30,9 @@
 
 // Constrained immediate argument types
 foreach SIZE = [8, 16] in
-def ImmI#SIZE : ImmLeaf<i32, "return (Imm & ((1UL << "#SIZE#") - 1)) == Imm;">;
+def ImmI#SIZE : ImmLeaf<i32,
+  "return ((uint64_t)Imm & ((1UL << "#SIZE#") - 1)) == (uint64_t)Imm;"
+>;
 foreach SIZE = [2, 4, 8, 16, 32] in
 def LaneIdx#SIZE : ImmLeaf<i32, "return 0 <= Imm && Imm < "#SIZE#";">;