runtime: precisely scan globals on all platforms

transform/testdata/optimizer-alloc-uses.ll

@@ -0,0 +1,20 @@
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown-wasm"
+
+@allocFunction = constant ptr @runtime.alloc
+
+declare ptr @runtime.alloc(i32, ptr)
+
+declare void @use(ptr)
+
+define void @passAllocator() {
+entry:
+  call void @use(ptr @runtime.alloc)
+  ret void
+}
+
+define ptr @allocate() {
+entry:
+  %allocation = call ptr @runtime.alloc(i32 4, ptr inttoptr (i32 5 to ptr))
+  ret ptr %allocation
+}