Merge pull request swiftlang#30748 from aschwaighofer/irgen_disable_typelayout_witness_at_onone

IRGen: Disable type layout based value witness generation at Onone

Author: aschwaighofer

lib/Frontend/CompilerInvocation.cpp

@@ -1292,6 +1292,9 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
                                OPT_disable_type_layouts)) {
     Opts.UseTypeLayoutValueHandling
       = A->getOption().matches(OPT_enable_type_layouts);
+  } else if (Opts.OptMode == OptimizationMode::NoOptimization) {
+    // Disable type layouts at Onone except if explictly requested.
+    Opts.UseTypeLayoutValueHandling = false;
   }
 
   Opts.UseSwiftCall = Args.hasArg(OPT_enable_swiftcall);

test/IRGen/typelayout_based_value_witness.swift

@@ -1,5 +1,6 @@
 // RUN: %target-swift-frontend -enable-type-layout -primary-file %s -emit-ir | %FileCheck %s --check-prefix=CHECK
 // RUN: %target-swift-frontend -enable-type-layout -primary-file %s -O -emit-ir | %FileCheck %s --check-prefix=OPT --check-prefix=OPT-%target-ptrsize
+// RUN: %target-swift-frontend -primary-file %s -emit-ir | %FileCheck %s --check-prefix=NOTL
 
 public struct B<T> {
   var x: T
@@ -11,6 +12,10 @@ public struct A<T> {
   var b:  B<T>
 }
 
+// NOTL-LABEL: define{{.*}} %swift.opaque* @"$s30typelayout_based_value_witness1AVwCP"(
+// NOTL:   @"$s30typelayout_based_value_witness1BVMa"(
+// NOTL: }
+
 // CHECK-LABEL: define{{.*}} %swift.opaque* @"$s30typelayout_based_value_witness1AVwCP"(
 // CHECK-NOT:   @"$s30typelayout_based_value_witness1BVMa"(
 // CHECK: }