Translate await bytecode into call to builtin

Summary: Add translation of hhbc await instruction (we previously only called the builtin for awaits on function calls and panicked on `await $a`). This supports inferhack unawaited awaitable analysis (D45861645)

Reviewed By: aorenste

Differential Revision: D45863376

fbshipit-source-id: f9ecffa176e4dbb97ee7ca7da35e4032a6c00b18

hphp/hack/src/hackc/ir/conversions/textual/func.rs

@@ -968,7 +968,7 @@ fn write_call(state: &mut FuncState<'_, '_, '_>, iid: InstrId, call: &ir::Call)
     };
 
     if is_async {
-        output = state.call_builtin(hack::Builtin::Await, [output])?;
+        output = state.call_builtin(hack::Builtin::Hhbc(hack::Hhbc::Await), [output])?;
     }
 
     state.set_iid(iid, output);

hphp/hack/src/hackc/ir/conversions/textual/hack.rs

@@ -46,6 +46,8 @@ pub(crate) enum Hhbc {
     AddElemC,
     #[decl(fn hhbc_add_new_elem_c(*HackMixed, *HackMixed) -> *HackMixed)]
     AddNewElemC,
+    #[decl(fn hhbc_await(*HackMixed) -> *HackMixed)]
+    Await,
     #[decl(fn hhbc_await_all(...) -> *HackMixed)]
     AwaitAll,
     #[decl(fn hhbc_cast_keyset(*HackMixed) -> *HackMixed)]
@@ -209,9 +211,6 @@ pub(crate) enum Builtin {
     /// pointer-sized value).
     #[decl(fn alloc_words(int) -> *void)]
     AllocWords,
-    /// Await for a value returned by an async function.
-    #[decl(fn await(*HackMixed) -> *HackMixed)]
-    Await,
     /// Get the superglobal as a base.
     #[decl(fn hack_base_get_superglobal(name: *HackMixed) -> **HackMixed)]
     BaseGetSuperglobal,

hphp/hack/src/hackc/ir/conversions/textual/lower/instrs.rs

@@ -97,6 +97,7 @@ impl LowerInstrs<'_> {
             Hhbc::Add(..) => hack::Hhbc::Add,
             Hhbc::AddElemC(..) => hack::Hhbc::AddElemC,
             Hhbc::AddNewElemC(..) => hack::Hhbc::AddNewElemC,
+            Hhbc::Await(..) => hack::Hhbc::Await,
             Hhbc::AwaitAll(..) => hack::Hhbc::AwaitAll,
             Hhbc::CastKeyset(..) => hack::Hhbc::CastKeyset,
             Hhbc::CastVec(..) => hack::Hhbc::CastVec,

hphp/hack/src/hackc/test/infer/async.hack

@@ -2,23 +2,38 @@
 
 // TEST-CHECK-BAL: define $root.test_async
 // CHECK: define $root.test_async($this: *void) : *HackInt {
-// CHECK: local $a: *void, $b: *void
+// CHECK: local $a: *void, $a2: *void, $b: *void
 // CHECK: #b0:
 // CHECK:   n0 = $root.bar(null)
-// CHECK:   n1 = $builtins.await(n0)
+// CHECK:   n1 = $builtins.hhbc_await(n0)
 // CHECK:   store &$a <- n1: *HackMixed
 // CHECK:   n2: *HackMixed = load &$a
 // CHECK:   n3 = $root.baz(null, n2)
-// CHECK:   n4 = $builtins.await(n3)
+// CHECK:   n4 = $builtins.hhbc_await(n3)
 // CHECK:   store &$b <- n4: *HackMixed
-// CHECK:   n5: *HackMixed = load &$b
-// CHECK:   n6 = $builtins.hhbc_is_type_int(n5)
-// CHECK:   n7 = $builtins.hhbc_verify_type_pred(n5, n6)
-// CHECK:   ret n5
+// CHECK:   n5 = $root.bar(null)
+// CHECK:   store &$a2 <- n5: *HackMixed
+// CHECK:   n6: *HackMixed = load &$a2
+// CHECK:   n7 = $builtins.hhbc_is_type_null(n6)
+// CHECK:   jmp b1, b2
+// CHECK: #b1:
+// CHECK:   prune $builtins.hack_is_true(n7)
+// CHECK:   jmp b3(n6)
+// CHECK: #b2:
+// CHECK:   prune ! $builtins.hack_is_true(n7)
+// CHECK:   n8 = $builtins.hhbc_await(n6)
+// CHECK:   jmp b3(n8)
+// CHECK: #b3(n9: *HackMixed):
+// CHECK:   n10: *HackMixed = load &$b
+// CHECK:   n11 = $builtins.hhbc_is_type_int(n10)
+// CHECK:   n12 = $builtins.hhbc_verify_type_pred(n10, n11)
+// CHECK:   ret n10
 // CHECK: }
 async function test_async(): Awaitable<int> {
   $a = await bar();
   $b = await baz($a);
+  $a2 = bar();
+  await $a2;
   return $b;
 }