[wasm] Make compilation more predictable

If predictable compilation is requested (via --predictable,
--single-threaded, or --wasm-num-compilation-tasks=0), do compile and
commit one function at a time. This makes function allocation
independent of the timing.

R=ahaas@chromium.org

Bug: v8:9751, v8:9752
Change-Id: I451a436800c19574caa5e03901bd900d80e53eee
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1809371Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63884}

src/wasm/module-compiler.cc

@@ -964,6 +964,10 @@ bool ExecuteJSToWasmWrapperCompilationUnits(
   return true;
 }
 
+bool NeedsDeterministicCompile() {
+  return FLAG_trace_wasm_decoder || FLAG_wasm_num_compilation_tasks <= 1;
+}
+
 // Run by the main thread and background tasks to take part in compilation.
 // Returns whether any units were executed.
 bool ExecuteCompilationUnits(
@@ -991,6 +995,7 @@ bool ExecuteCompilationUnits(
   // These fields are initialized in a {BackgroundCompileScope} before
   // starting compilation.
   double deadline = 0;
+  const bool deterministic = NeedsDeterministicCompile();
   base::Optional<CompilationEnv> env;
   std::shared_ptr<WireBytesStorage> wire_bytes;
   std::shared_ptr<const WasmModule> module;
@@ -1084,7 +1089,7 @@ bool ExecuteCompilationUnits(
       }
 
       // Get next unit.
-      if (deadline < platform->MonotonicallyIncreasingTime()) {
+      if (deterministic || deadline < platform->MonotonicallyIncreasingTime()) {
         unit = {};
       } else {
         unit = compile_scope.compilation_state()->GetNextCompilationUnit(
@@ -1196,10 +1201,6 @@ void InitializeCompilationUnits(Isolate* isolate, NativeModule* native_module) {
   builder.Commit();
 }
 
-bool NeedsDeterministicCompile() {
-  return FLAG_trace_wasm_decoder || FLAG_wasm_num_compilation_tasks <= 1;
-}
-
 bool MayCompriseLazyFunctions(const WasmModule* module,
                               const WasmFeatures& enabled_features,
                               bool lazy_module) {