Debug Info: Support updates to debug values.

This allows SIL transformations to describe one source variable with more
than one debug_value instruction.

rdar://problem/22705966

Author: adrian-prantl

lib/IRGen/IRGenSIL.cpp

@@ -292,6 +292,9 @@ class IRGenSILFunction :
 
   /// All alloc_ref instructions which allocate the object on the stack.
   llvm::SmallPtrSet<SILInstruction *, 8> StackAllocs;
+  /// Keeps track of the mapping of source variables to -O0 shadow copy allocas.
+  llvm::SmallDenseMap<std::pair<const SILDebugScope *, StringRef>, Address, 8>
+      ShadowStackSlots;
 
   /// Accumulative amount of allocated bytes on the stack. Used to limit the
   /// size for stack promoted objects.
@@ -483,6 +486,7 @@ class IRGenSILFunction :
   /// register pressure is high.  There is a trade-off to this: With
   /// shadow copies, we lose the precise lifetime.
   llvm::Value *emitShadowCopy(llvm::Value *Storage,
+                              const SILDebugScope *Scope,
                               StringRef Name,
                               Alignment Align = Alignment(0)) {
     auto Ty = Storage->getType();
@@ -495,16 +499,21 @@ class IRGenSILFunction :
     if (Align.isZero())
       Align = IGM.getPointerAlignment();
 
-    auto Alloca = createAlloca(Ty, Align, Name+".addr");
+    auto &Alloca = ShadowStackSlots[{Scope, Name}];
+    if (!Alloca.isValid())
+      Alloca = createAlloca(Ty, Align, Name+".addr");
     Builder.CreateStore(Storage, Alloca.getAddress(), Align);
     return Alloca.getAddress();
   }
 
-  llvm::Value *emitShadowCopy(Address storage, StringRef name) {
-    return emitShadowCopy(storage.getAddress(), name, storage.getAlignment());
+  llvm::Value *emitShadowCopy(Address Storage, const SILDebugScope *Scope,
+                              StringRef Name) {
+    return emitShadowCopy(Storage.getAddress(), Scope, Name,
+                          Storage.getAlignment());
   }
 
-  void emitShadowCopy(ArrayRef<llvm::Value *> vals, StringRef name,
+  void emitShadowCopy(ArrayRef<llvm::Value *> vals, const SILDebugScope *scope,
+                      StringRef name,
                       llvm::SmallVectorImpl<llvm::Value *> &copy) {
     // Only do this at -O0.
     if (IGM.Opts.Optimize) {
@@ -515,7 +524,7 @@ class IRGenSILFunction :
     // Single or empty values.
     if (vals.size() <= 1) {
       for (auto val : vals)
-        copy.push_back(emitShadowCopy(val, name));
+        copy.push_back(emitShadowCopy(val, scope, name));
       return;
     }
 
@@ -1402,8 +1411,9 @@ void IRGenSILFunction::emitFunctionArgDebugInfo(SILBasicBlock *BB) {
     unsigned ArgNo =
         countArgs(CurSILFn->getDeclContext()) + 1 + BB->getBBArgs().size();
     IGM.DebugInfo->emitVariableDeclaration(
-        Builder, emitShadowCopy(ErrorResultSlot.getAddress(), Name), DTI,
-        getDebugScope(), Name, ArgNo, IndirectValue, ArtificialValue);
+        Builder,
+        emitShadowCopy(ErrorResultSlot.getAddress(), getDebugScope(), Name),
+        DTI, getDebugScope(), Name, ArgNo, IndirectValue, ArtificialValue);
   }
 }
 
@@ -2935,24 +2945,29 @@ void IRGenSILFunction::visitDebugValueInst(DebugValueInst *i) {
   if (!IGM.DebugInfo)
     return;
 
-  VarDecl *Decl = i->getDecl();
-  if (!Decl)
-    return;
-
   auto SILVal = i->getOperand();
   if (isa<SILUndef>(SILVal))
     return;
 
   StringRef Name = i->getVarInfo().Name;
-  Explosion e = getLoweredExplosion(SILVal);
-  DebugTypeInfo DbgTy(Decl, Decl->getType(), getTypeInfo(SILVal.getType()));
+  DebugTypeInfo DbgTy;
+  SILType SILTy = SILVal.getType();
+  if (VarDecl *Decl = i->getDecl())
+    DbgTy = DebugTypeInfo(Decl, Decl->getType(), getTypeInfo(SILTy));
+  else if (i->getFunction()->isBare() &&
+           !SILTy.getSwiftType()->hasArchetype() && !Name.empty())
+    // Preliminary support for .sil debug information.
+    DbgTy = DebugTypeInfo(SILTy.getSwiftType(), getTypeInfo(SILTy), nullptr);
+  else
+    return;
   // An inout/lvalue type that is described by a debug value has been
   // promoted by an optimization pass. Unwrap the type.
   DbgTy.unwrapLValueOrInOutType();
 
   // Put the value into a stack slot at -Onone.
-  llvm::SmallVector<llvm::Value *, 8> Copy;
-  emitShadowCopy(e.claimAll(), Name, Copy);
+  llvm::SmallVector<llvm::Value *, 8> Copy; 
+  Explosion e = getLoweredExplosion(SILVal);
+  emitShadowCopy(e.claimAll(), i->getDebugScope(), Name, Copy);
   emitDebugVariableDeclaration(Copy, DbgTy, i->getDebugScope(), Name,
                                i->getVarInfo().ArgNo);
 }
@@ -2972,9 +2987,9 @@ void IRGenSILFunction::visitDebugValueAddrInst(DebugValueAddrInst *i) {
   auto Addr = getLoweredAddress(SILVal).getAddress();
   DebugTypeInfo DbgTy(Decl, Decl->getType(), getTypeInfo(SILVal.getType()));
   // Put the value into a stack slot at -Onone and emit a debug intrinsic.
-  emitDebugVariableDeclaration(emitShadowCopy(Addr, Name), DbgTy,
-                               i->getDebugScope(), Name,
-                               i->getVarInfo().ArgNo, IndirectValue);
+  emitDebugVariableDeclaration(
+      emitShadowCopy(Addr, i->getDebugScope(), Name), DbgTy,
+      i->getDebugScope(), Name, i->getVarInfo().ArgNo, IndirectValue);
 }
 
 void IRGenSILFunction::visitLoadWeakInst(swift::LoadWeakInst *i) {
@@ -3390,7 +3405,7 @@ void IRGenSILFunction::visitAllocBoxInst(swift::AllocBoxInst *i) {
       return;
 
     IGM.DebugInfo->emitVariableDeclaration(
-        Builder, emitShadowCopy(addr.getAddress(), Name),
+        Builder, emitShadowCopy(addr.getAddress(), i->getDebugScope(), Name),
         DebugTypeInfo(Decl, i->getElementType().getSwiftType(), type),
         i->getDebugScope(), Name, 0, IndirectValue);
   }

test/DebugInfo/value-update.sil

@@ -0,0 +1,47 @@
+// RUN: %target-swift-frontend %s -emit-ir -module-name test -g -o - | FileCheck %s
+// REQUIRES: CPU=x86_64
+sil_stage canonical
+
+import Builtin
+import Swift
+import SwiftShims
+
+// test.foo () -> ()
+sil @_TF4test3fooFT_T_ : $@convention(thin) () -> () {
+bb0:
+  %1 = integer_literal $Builtin.Int64, 23
+  %2 = struct $Int (%1 : $Builtin.Int64)
+  debug_value %2 : $Int, var, name "v"
+  // CHECK: store i64 23, i64* %[[ALLOCA:.*]], align 8, !dbg
+  // CHECK: dbg.declare
+  // function_ref StdlibUnittest._blackHole <A> (A) -> ()
+  %5 = function_ref @_TF14StdlibUnittest10_blackHoleurFxT_ : $@convention(thin) <τ_0_0> (@in τ_0_0) -> () // user: %8
+  %6 = tuple ()
+  %7 = alloc_stack $()                            // users: %8, %9
+  %8 = apply %5<()>(%7#1) : $@convention(thin) <τ_0_0> (@in τ_0_0) -> ()
+  dealloc_stack %7#0 : $*@local_storage ()        // id: %9
+
+  // CHECK: store i64 42, i64* %[[ALLOCA]], align 8, !dbg
+  // CHECK-NOT: dbg.declare
+  %9 = integer_literal $Builtin.Int64, 42         // user: %10
+  %10 = struct $Int (%9 : $Builtin.Int64)         // user: %11
+  debug_value %10 : $Int, var, name "v"
+
+  // function_ref StdlibUnittest._blackHole <A> (A) -> ()
+  %13 = function_ref @_TF14StdlibUnittest10_blackHoleurFxT_ : $@convention(thin) <τ_0_0> (@in τ_0_0) -> () // user: %16
+  %14 = tuple ()
+  %15 = alloc_stack $()                           // users: %16, %17
+  %16 = apply %13<()>(%15#1) : $@convention(thin) <τ_0_0> (@in τ_0_0) -> ()
+  dealloc_stack %15#0 : $*@local_storage ()       // id: %17
+
+  %18 = tuple ()                                  // user: %21
+  return %18 : $()                                // id: %21
+  // CHECK: {{^}}}
+}
+
+// Swift.Int.init (_builtinIntegerLiteral : Builtin.Int2048) -> Swift.Int
+sil [transparent] [fragile] @_TFSiCfT22_builtinIntegerLiteralBi2048__Si : $@convention(thin) (Builtin.Int2048, @thin Int.Type) -> Int
+
+// StdlibUnittest._blackHole <A> (A) -> ()
+sil @_TF14StdlibUnittest10_blackHoleurFxT_ : $@convention(thin) <τ_0_0> (@in τ_0_0) -> ()
+