Emit compiler-generated debug locations for outlined transparent functions.

In the majority of the use-cases transparent functions are inlined by
the mandatory inliner which by design drops all debug info and
pretends the inlined instructions were always part of the
caller. Since an outlined copy of the function is often still
generated, attaching debug locations to it is inconsistent and can
create the false impression that it were possible to set a breakpoint
in such a function when in reality these functions are only there for
very few edge cases.

<rdar://problem/40258813>

Author: adrian-prantl

lib/IRGen/GenProto.cpp

@@ -3332,7 +3332,8 @@ irgen::emitAssociatedTypeMetadataRef(IRGenFunction &IGF,
   FunctionPointer witnessFnPtr(witness, sig);
 
   // Call the accessor.
-  assert((!IGF.IGM.DebugInfo || IGF.Builder.getCurrentDebugLocation()) &&
+  assert((!IGF.IGM.DebugInfo || IGF.Builder.getCurrentDebugLocation() ||
+          !IGF.CurFn->getSubprogram()) &&
          "creating a function call without a debug location");
   auto call = IGF.Builder.CreateCall(witnessFnPtr,
                                      { request.get(IGF),

lib/IRGen/IRGenDebugInfo.cpp

@@ -286,6 +286,9 @@ class IRGenDebugInfoImpl : public IRGenDebugInfo {
 
     auto L = decodeDebugLoc(CS->Loc);
     auto Scope = getOrCreateScope(CS->Parent.dyn_cast<const SILDebugScope *>());
+    // Pretend transparent functions don't exist.
+    if (!Scope)
+      return createInlinedAt(CS);
     auto InlinedAt =
         llvm::DebugLoc::get(L.Line, L.Column, Scope, createInlinedAt(CS));
     InlinedAtCache.insert(
@@ -1563,7 +1566,7 @@ void IRGenDebugInfoImpl::setCurrentLoc(IRBuilder &Builder,
 
   SILLocation::DebugLoc L;
   SILFunction *Fn = DS->getInlinedFunction();
-  if (Fn && Fn->isThunk()) {
+  if (Fn && (Fn->isThunk() || Fn->isTransparent())) {
     L = SILLocation::getCompilerGeneratedDebugLoc();
   } else if (DS == LastScope && Loc.isAutoGenerated()) {
     // Reuse the last source location if we are still in the same
@@ -1735,6 +1738,7 @@ IRGenDebugInfoImpl::emitFunction(const SILDebugScope *DS, llvm::Function *Fn,
   // Some IRGen-generated helper functions don't have a corresponding
   // SIL function, hence the dyn_cast.
   auto *SILFn = DS ? DS->Parent.dyn_cast<SILFunction *>() : nullptr;
+
   StringRef LinkageName;
   if (Fn)
     LinkageName = Fn->getName();
@@ -1754,17 +1758,18 @@ IRGenDebugInfoImpl::emitFunction(const SILDebugScope *DS, llvm::Function *Fn,
   /// The source line used for the function prologue.
   unsigned ScopeLine = 0;
   SILLocation::DebugLoc L;
-  if (DS && (!SILFn || (!SILFn->isBare() && !SILFn->isThunk()))) {
+  if (!DS || (SILFn && (SILFn->isBare() || SILFn->isThunk() ||
+                        SILFn->isTransparent()))) {
     // Bare functions and thunks should not have any line numbers. This
     // is especially important for shared functions like reabstraction
     // thunk helpers, where DS->Loc is an arbitrary location of whichever use
     // was emitted first.
+    L = SILLocation::getCompilerGeneratedDebugLoc();
+  } else {
     L = decodeDebugLoc(DS->Loc);
     ScopeLine = L.Line;
     if (!DS->Loc.isDebugInfoLoc())
       L = decodeSourceLoc(DS->Loc.getSourceLoc());
-  } else {
-    L = SILLocation::getCompilerGeneratedDebugLoc();
   }
 
   auto Line = L.Line;
@@ -1882,7 +1887,7 @@ void IRGenDebugInfoImpl::emitVariableDeclaration(
   if (!DbgTy.size)
     DbgTy.size = getStorageSize(IGM.DataLayout, Storage);
 
-  auto *Scope = dyn_cast<llvm::DILocalScope>(getOrCreateScope(DS));
+  auto *Scope = dyn_cast_or_null<llvm::DILocalScope>(getOrCreateScope(DS));
   assert(Scope && "variable has no local scope");
   auto Loc = getDebugLoc(*this, VarDecl);
 
@@ -2028,13 +2033,17 @@ void IRGenDebugInfoImpl::emitTypeMetadata(IRGenFunction &IGF,
   if (Opts.DebugInfoKind <= IRGenDebugInfoKind::LineTables)
     return;
 
+  // Don't emit debug info in transparent functions.
+  auto *DS = IGF.getDebugScope();
+  if (!DS || DS->getInlinedFunction()->isTransparent())
+    return;
+
   auto TName = BumpAllocatedString(("$swift.type." + Name).str());
   auto DbgTy = DebugTypeInfo::getMetadata(
       getMetadataType()->getDeclaredInterfaceType().getPointer(),
       Metadata->getType(), Size(CI.getTargetInfo().getPointerWidth(0)),
       Alignment(CI.getTargetInfo().getPointerAlign(0)));
-  emitVariableDeclaration(IGF.Builder, Metadata, DbgTy, IGF.getDebugScope(),
-                          nullptr, TName, 0,
+  emitVariableDeclaration(IGF.Builder, Metadata, DbgTy, DS, nullptr, TName, 0,
                           // swift.type is already a pointer type,
                           // having a shadow copy doesn't add another
                           // layer of indirection.

lib/IRGen/IRGenSIL.cpp

@@ -1771,8 +1771,8 @@ void IRGenSILFunction::visitSILBasicBlock(SILBasicBlock *BB) {
   for (auto &I : *BB) {
     if (IGM.DebugInfo) {
       // Set the debug info location for I, if applicable.
-      SILLocation ILoc = I.getLoc();
       auto DS = I.getDebugScope();
+      SILLocation ILoc = I.getLoc();
       // Handle cleanup locations.
       if (ILoc.is<CleanupLocation>()) {
         // Cleanup locations point to the decl of the value that is
@@ -1830,9 +1830,8 @@ void IRGenSILFunction::visitSILBasicBlock(SILBasicBlock *BB) {
         emitDebugVariableRangeExtension(BB);
     }
     visit(&I);
-
   }
-  
+
   assert(Builder.hasPostTerminatorIP() && "SIL bb did not terminate block?!");
 }
 
@@ -3647,6 +3646,9 @@ void IRGenSILFunction::visitDebugValueInst(DebugValueInst *i) {
   if (!IGM.DebugInfo)
     return;
 
+  if (i->getDebugScope()->getInlinedFunction()->isTransparent())
+    return;
+  
   auto VarInfo = i->getVarInfo();
   assert(VarInfo && "debug_value without debug info");
   auto SILVal = i->getOperand();
@@ -3689,6 +3691,10 @@ void IRGenSILFunction::visitDebugValueInst(DebugValueInst *i) {
 void IRGenSILFunction::visitDebugValueAddrInst(DebugValueAddrInst *i) {
   if (!IGM.DebugInfo)
     return;
+
+  if (i->getDebugScope()->getInlinedFunction()->isTransparent())
+    return;
+
   VarDecl *Decl = i->getDecl();
   if (!Decl)
     return;
@@ -3968,6 +3974,9 @@ void IRGenSILFunction::emitDebugInfoForAllocStack(AllocStackInst *i,
   if (!DS)
     return;
 
+  if (i->getDebugScope()->getInlinedFunction()->isTransparent())
+    return;
+  
   bool IsAnonymous = false;
   StringRef Name = getVarName(i, IsAnonymous);
 
@@ -4171,6 +4180,9 @@ void IRGenSILFunction::visitAllocBoxInst(swift::AllocBoxInst *i) {
                                              DbgName);
   setLoweredBox(i, boxWithAddr);
 
+  if (i->getDebugScope()->getInlinedFunction()->isTransparent())
+    return;
+  
   if (IGM.DebugInfo && Decl) {
     // FIXME: This is a workaround to not produce local variables for
     // capture list arguments like "[weak self]". The better solution

test/DebugInfo/autoclosure.swift

@@ -21,7 +21,7 @@ func &&&&&(lhs: Bool, rhs: @autoclosure () -> Bool) -> Bool {
 func call_me(_ input: Int64) -> Void {
 // rdar://problem/14627460
 // An autoclosure should have a line number in the debug info and a scope line of 0.
-// CHECK-DAG: !DISubprogram({{.*}}linkageName: "$S11autoclosure7call_meyys5Int64VFSbyXKfu_",{{.*}} line: [[@LINE+3]],{{.*}} isLocal: true, isDefinition: true
+// CHECK-DAG: !DISubprogram({{.*}}linkageName: "$S11autoclosure7call_meyys5Int64VFSbyXKfu_",{{.*}} isLocal: true, isDefinition: true
 // But not in the line table.
 // CHECK-DAG: ![[DBG]] = !DILocation(line: [[@LINE+1]],
   if input != 0 &&&&& ( get_truth (input * 2 + 1) > 0 ) {

test/DebugInfo/generic_enum_closure.swift

@@ -15,9 +15,8 @@ struct CErrorOr<T>
     // CHECK-SAME: !DIExpression(DW_OP_deref))
     // CHECK-DAG: store i8* %[[DYN:.*]], i8** %[[SHADOW]]
     // CHECK-DAG: %[[DYN]] = alloca i8, i{{32|64}} %
-    // CHECK: ![[T1:.*]] = !DICompositeType({{.*}}, identifier: "$S20generic_enum_closure8CErrorOrVyACQq_GD")
-    // CHECK: ![[SELF]] = !DILocalVariable(name: "self", scope:
-    // CHECK-SAME:                         type: ![[T1]])
+    // CHECK-DAG: ![[T1:.*]] = !DICompositeType({{.*}}, identifier: "$S20generic_enum_closure8CErrorOrVyACQq_GD")
+    // CHECK-DAG: ![[SELF]] = !DILocalVariable(name: "self", scope:{{.*}}, type: ![[T1]])
     value = .none
   }
 }

test/DebugInfo/transparent.swift

@@ -0,0 +1,29 @@
+// RUN: %target-swift-frontend %s -O -I %t -emit-ir -g -o - | %FileCheck %s
+
+func use<T>(_ t: T) {}
+
+@inline(never)
+public func noinline(_ x: Int64) -> Int64 { return x }
+
+@_transparent
+public func transparent(_ y: Int64) -> Int64 {
+  var local = y
+  return noinline(local)
+}
+
+let z = transparent(0)
+use(z)
+
+// Check that a transparent function has no debug information.
+// CHECK: define {{.*}}$S11transparentAA
+// CHECK-SAME: !dbg ![[SP:[0-9]+]]
+// CHECK-NEXT: entry:
+// CHECK-NEXT: !dbg ![[ZERO:[0-9]+]]
+// CHECK-NEXT: !dbg ![[ZERO]]
+// CHECK-NEXT: }
+
+// CHECK: ![[SP]] = {{.*}}name: "transparent"
+// CHECK-SAME: file: ![[FILE:[0-9]+]]
+// CHECK-NOT: line:
+// CHECK: ![[FILE]] = {{.*}}"<compiler-generated>"
+// CHECK: ![[ZERO]] = !DILocation(line: 0,