IRGen: Annotate LLVM IR of condfail with the condfail's message

`-Xfrontend -enable-cond-fail-message-annotation`
LLVM IR produced by the Swift compiler will add the `annotation`
metadata attribute to the branch instruction generated for cond_fail
builtins.

Author: aschwaighofer

include/swift/AST/IRGenOptions.h

@@ -490,6 +490,8 @@ class IRGenOptions {
 
   unsigned ConditionalRuntimeRecords : 1;
 
+  unsigned AnnotateCondFailMessage : 1;
+
   unsigned InternalizeAtLink : 1;
 
   /// Internalize symbols (static library) - do not export any public symbols.
@@ -634,6 +636,7 @@ class IRGenOptions {
         DisableStandardSubstitutionsInReflectionMangling(false),
         EnableGlobalISel(false), VirtualFunctionElimination(false),
         WitnessMethodElimination(false), ConditionalRuntimeRecords(false),
+        AnnotateCondFailMessage(false),
         InternalizeAtLink(false), InternalizeSymbols(false),
         MergeableSymbols(false), EmitGenericRODatas(true),
         NoPreallocatedInstantiationCaches(false),

include/swift/Option/FrontendOptions.td

@@ -1175,6 +1175,12 @@ def enable_arm64_corocc : Flag<["-"], "enable-arm64-corocc">,
 def disable_arm64_corocc : Flag<["-"], "disable-arm64-corocc">,
   HelpText<"Don't use swiftcorocc for yield_once_2 routines on arm64 variants.">;
 
+def enable_cond_fail_message_annotation : Flag<["-"], "enable-cond-fail-message-annotation">,
+  HelpText<"Enable large loadable types register to memory pass">;
+
+def disable_cond_fail_message_annotation : Flag<["-"], "dissable-cond-fail-message-annotation">,
+  HelpText<"Disable large loadable types register to memory pass">;
+
 let Flags = [FrontendOption, NoDriverOption, HelpHidden, ModuleInterfaceOptionIgnorable] in {
   def enable_pack_metadata_stack_promotion :
     Joined<["-"], "enable-pack-metadata-stack-promotion=">,

lib/Frontend/CompilerInvocation.cpp

@@ -3764,6 +3764,11 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
   Opts.EnableLayoutStringValueWitnessesInstantiation = Args.hasFlag(OPT_enable_layout_string_value_witnesses_instantiation,
                                       OPT_disable_layout_string_value_witnesses_instantiation,
                                       Opts.EnableLayoutStringValueWitnessesInstantiation);
+  Opts.AnnotateCondFailMessage =
+      Args.hasFlag(OPT_enable_cond_fail_message_annotation,
+                   OPT_disable_cond_fail_message_annotation,
+                   Opts.AnnotateCondFailMessage);
+
 
   if (Opts.EnableLayoutStringValueWitnessesInstantiation &&
       !Opts.EnableLayoutStringValueWitnesses) {

lib/IRGen/IRGenSIL.cpp

@@ -8249,8 +8249,11 @@ void IRGenSILFunction::visitCondFailInst(swift::CondFailInst *i) {
 
   llvm::BasicBlock *failBB = llvm::BasicBlock::Create(IGM.getLLVMContext());
   llvm::BasicBlock *contBB = llvm::BasicBlock::Create(IGM.getLLVMContext());
-  Builder.CreateCondBr(expectedCond, failBB, contBB);
-    
+  auto br = Builder.CreateCondBr(expectedCond, failBB, contBB);
+
+  if (IGM.getOptions().AnnotateCondFailMessage && !i->getMessage().empty())
+    br->addAnnotationMetadata(i->getMessage());
+
   Builder.SetInsertPoint(&CurFn->back());
   Builder.emitBlock(failBB);
   if (IGM.DebugInfo)

test/IRGen/annotated_cond_fail.swift

@@ -0,0 +1,27 @@
+// RUN: %target-swift-frontend -module-name A -enable-cond-fail-message-annotation -primary-file %s -O -emit-ir | %FileCheck %s
+
+// REQUIRES: swift_stdlib_no_asserts,optimized_stdlib
+// REQUIRES: PTRSIZE=64
+
+public func test(_ a: [Int], _ i: Int) -> Int {
+    return a[i + 1]
+}
+
+// CHECK: define{{.*}} swiftcc i64 @"$s1A4testySiSaySiG_SitF"(ptr{{.*}} %0, i64 %1)
+
+// CHECK:  [[ADD:%.*]] = tail call { i64, i1 } @llvm.sadd.with.overflow.i64(i64 %1, i64 1)
+// CHECK:  [[IDX:%.*]] = extractvalue { i64, i1 } [[ADD]], 0
+// CHECK:  [[OVERFLOW:%.*]] = extractvalue { i64, i1 } [[ADD]], 1
+// CHECK:  br i1 [[OVERFLOW]], {{.*}}!annotation ![[ARITH_OVERFLOW:[0-9]+]]
+
+// CHECK:  [[C0:%.*]] = icmp slt i64 [[IDX]], 0
+// CHECK:  br i1 [[C0]], {{.*}}!annotation ![[ARRAY_INDEX_OUT_OF_BOUNDS:[0-9]+]]
+
+// CHECK:  [[SIZE_ADDR:%.*]] = getelementptr
+// CHECK:  [[SIZE:%.*]] = load i64, ptr [[SIZE_ADDR]]
+// CHECK:  [[C1:%.*]] = icmp ult i64 [[IDX]], [[SIZE]]
+// CHECK:  br i1 [[C1]], {{.*}}!annotation ![[ARRAY_INDEX_OUT_OF_BOUNDS]]
+
+
+// CHECK-DAG: ![[ARITH_OVERFLOW]] = !{!"arithmetic overflow"}
+// CHECK-DAG: ![[ARRAY_INDEX_OUT_OF_BOUNDS]] = !{!"Index out of range"}