[DebugInfo] Add debug info support for recursive SIL SROA

This removes the restriction that only one fragment is allowed at
the end of a SIL DIExpression.

rdar://100046900

Author: Snowy1803

include/swift/SIL/SILDebugVariable.h

@@ -76,6 +76,10 @@ struct SILDebugVariable {
   static std::optional<SILDebugVariable>
   createFromAllocation(const AllocationInst *AI);
 
+  /// Return the underlying variable declaration that this denotes,
+  /// or nullptr if we don't have one.
+  VarDecl *getDecl() const;
+
   // We're not comparing DIExpr here because strictly speaking,
   // DIExpr is not part of the debug variable. We simply piggyback
   // it in this class so that's it's easier to carry DIExpr around.

lib/IRGen/IRGenDebugInfo.cpp

@@ -2938,21 +2938,19 @@ bool IRGenDebugInfoImpl::buildDebugInfoExpression(
     llvm::DIExpression::FragmentInfo &Fragment) {
   assert(VarInfo.DIExpr && "SIL debug info expression not found");
 
-#ifndef NDEBUG
-  bool HasFragment = VarInfo.DIExpr.hasFragment();
-#endif
-
   const auto &DIExpr = VarInfo.DIExpr;
   for (const SILDIExprOperand &ExprOperand : DIExpr.operands()) {
+    llvm::DIExpression::FragmentInfo SubFragment = {0, 0};
     switch (ExprOperand.getOperator()) {
     case SILDIExprOperator::Fragment:
-      assert(HasFragment && "Fragment must be the last part of a DIExpr");
-#ifndef NDEBUG
-      // Trigger the assert above if we have more than one fragment expression.
-      HasFragment = false;
-#endif
-      if (!handleFragmentDIExpr(ExprOperand, Fragment))
+      if (!handleFragmentDIExpr(ExprOperand, SubFragment))
         return false;
+      assert(!Fragment.SizeInBits
+             || (SubFragment.OffsetInBits + SubFragment.SizeInBits
+              <= Fragment.SizeInBits)
+             && "Invalid nested fragments");
+      Fragment.OffsetInBits += SubFragment.OffsetInBits;
+      Fragment.SizeInBits = SubFragment.SizeInBits;
       break;
     case SILDIExprOperator::Dereference:
       Operands.push_back(llvm::dwarf::DW_OP_deref);

lib/IRGen/IRGenSIL.cpp

@@ -5463,9 +5463,16 @@ void IRGenSILFunction::visitDebugValueInst(DebugValueInst *i) {
       assert(isa<SILBoxType>(RealTy));
     }
 
+  VarDecl *VD = i->getDecl();
+  if (!VD) {
+    // The source location of a DebugValueInst inserted by the SIL optimizer is
+    // not necessarily the VarDecl, as it can be the source location of the
+    // update point this DebugValueInst represents.
+    VD = VarInfo->getDecl();
+  }
   // Figure out the debug variable type
-  if (VarDecl *Decl = i->getDecl()) {
-    DbgTy = DebugTypeInfo::getLocalVariable(Decl, RealTy, getTypeInfo(SILTy),
+  if (VD) {
+    DbgTy = DebugTypeInfo::getLocalVariable(VD, RealTy, getTypeInfo(SILTy),
                                             IGM, IsFragmentType);
   } else if (!SILTy.hasArchetype() && !VarInfo->Name.empty()) {
     // Handle the cases that read from a SIL file

lib/SIL/IR/SILInstructions.cpp

@@ -208,10 +208,6 @@ SILDebugVariable::createFromAllocation(const AllocationInst *AI) {
   if (!VarInfo)
     return {};
 
-  // TODO: Support variables with expressions.
-  if (VarInfo->DIExpr)
-    return {};
-
   // Coalesce the debug loc attached on AI into VarInfo
   SILType Type = AI->getType();
   SILLocation InstLoc = AI->getLoc();
@@ -495,6 +491,12 @@ VarDecl *DebugValueInst::getDecl() const {
   return getLoc().getAsASTNode<VarDecl>();
 }
 
+VarDecl *SILDebugVariable::getDecl() const {
+  if (!Loc)
+    return nullptr;
+  return Loc->getAsASTNode<VarDecl>();
+}
+
 AllocExistentialBoxInst *AllocExistentialBoxInst::create(
     SILDebugLocation Loc, SILType ExistentialType, CanType ConcreteType,
     ArrayRef<ProtocolConformanceRef> Conformances,

lib/SIL/Verifier/SILVerifier.cpp

@@ -1469,6 +1469,7 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
 
     // Check debug info expression
     if (const auto &DIExpr = varInfo->DIExpr) {
+      bool HasFragment = false;
       for (auto It = DIExpr.element_begin(), ItEnd = DIExpr.element_end();
            It != ItEnd;) {
         require(It->getKind() == SILDIExprElement::OperatorKind,
@@ -1483,8 +1484,10 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
                   "di-expression operand kind mismatch");
 
         if (Op == SILDIExprOperator::Fragment)
-          require(It == ItEnd, "op_fragment directive needs to be at the end "
-                               "of a di-expression");
+          HasFragment = true;
+        else
+          require(!HasFragment, "no directive allowed after op_fragment"
+                  " in a di-expression");
       }
     }
   }

lib/SILOptimizer/Utils/InstOptUtils.cpp

@@ -1933,10 +1933,7 @@ void swift::createDebugFragments(SILValue oldValue, Projection proj,
     if (!debugVal)
       continue;
 
-    // Can't create a fragment of a fragment.
     auto varInfo = debugVal->getVarInfo();
-    if (!varInfo || varInfo->DIExpr.hasFragment())
-      continue;
 
     SILType baseType = oldValue->getType();
 

test/DebugInfo/sil_based_dbg.swift

@@ -29,13 +29,12 @@ struct TheStruct {
 }
 // CHECK_DBG_SCOPE-LABEL: sil {{.*}}test_debug_scope
 public func test_debug_scope(val : Int) -> Int {
-    // TODO: Repeated SROA of the same variable is currently disabled.
-    // CHECK_DBG_SCOPE: alloc_stack $Builtin.Int{{[0-9]+}}, 
-    // CHECK_DBG_SCOPE-NOT:                          var,
-    // DISABLED_DBG_SCOPE-SAME:                      var, (name "the_struct",
-    // DISABLED_DBG_SCOPE-SAME:                      loc
+    // CHECK_DBG_SCOPE: alloc_stack $Builtin.Int{{[0-9]+}},
+    // CHECK_DBG_SCOPE-SAME:  var, (name "the_struct",
+    // CHECK_DBG_SCOPE-SAME:  loc
+    // CHECK_DBG_SCOPE-SAME:  expr op_fragment:#TheStruct.the_member:op_fragment:#Int._value
     // The auxiliary debug scope should be removed
-    // DISABLED_DBG_SCOPE-NOT:                       scope {{[0-9]+}})
+    // CHECK_DBG_SCOPE-NOT:   scope {{[0-9]+}})
     var the_struct = TheStruct(the_member: 0)
     the_struct.the_member = val + 13
     return the_struct.the_member

test/DebugInfo/srosroa_mem2reg.sil

@@ -31,11 +31,10 @@ bb0(%0 : $Int64, %1 : $Int64):
   debug_value %0 : $Int64, let, name "in_x", argno 1, loc "sroa.swift":7:10, scope 2
   debug_value %1 : $Int64, let, name "in_y", argno 2, loc "sroa.swift":7:21, scope 2
   %4 = alloc_stack $MyStruct, var, name "my_struct", type $*MyContainer, expr op_fragment:#MyContainer.z, loc "sroa.swift":8:9, scope 2
-  // Recursive SROA of already SROA-ed aggregates is not yet supported.
   // CHECK-SROA:      alloc_stack $Int64
-  // CHECK-SROA-NOT:  var,
+  // CHECK-SROA-SAME: var,
   // CHECK-SROA:      alloc_stack $Int64
-  // CHECK-SROA-NOT:  var,
+  // CHECK-SROA-SAME: var,
   // CHECK-SROA:      metatype
   %5 = metatype $@thin MyStruct.Type, loc "sroa.swift":8:21, scope 2
   %6 = integer_literal $Builtin.Int64, 0, loc "sroa.swift":8:33, scope 2

test/DebugInfo/verifier_debug_info_expression.sil

@@ -1,4 +1,4 @@
-// RUN: not --crash %target-swift-frontend %s -sil-verify-all -g -emit-sil
+// RUN: %target-swift-frontend %s -sil-verify-all -g -emit-sil | %FileCheck %s
 import Builtin
 import Swift
 
@@ -11,11 +11,12 @@ sil_scope 1 { loc "file.swift":7:6 parent @test_fragment : $@convention(thin) ()
 
 sil hidden @test_fragment : $@convention(thin) () -> () {
 bb0:
-  %2 = alloc_stack $MyStruct, var, name "my_struct", loc "file.swift":8:9, scope 1
-  %3 = struct_element_addr %2 : $*MyStruct, #MyStruct.x, loc "file.swift":9:17, scope 1
-  // every op_fragment should be the last di-expression operand
-  debug_value %3 : $*Builtin.Int64, var, name "my_struct", expr op_deref:op_fragment:#MyStruct.y:op_fragment:#MyStruct.x
-  dealloc_stack %2 : $*MyStruct
+  %0 = alloc_stack $MyStruct, var, name "my_struct", loc "file.swift":8:9, scope 1
+  %1 = struct_element_addr %0 : $*MyStruct, #MyStruct.x, loc "file.swift":9:17, scope 1
+  // nested op_fragments at the end are allowed
+  // CHECK: debug_value %1 : $*Builtin.Int64, var, name "my_struct", expr op_deref:op_fragment:#MyStruct.y:op_fragment:#MyStruct.x
+  debug_value %1 : $*Builtin.Int64, var, name "my_struct", expr op_deref:op_fragment:#MyStruct.y:op_fragment:#MyStruct.x
+  dealloc_stack %0 : $*MyStruct
   %r = tuple()
   return %r : $()
 }

test/DebugInfo/verifier_debug_info_expression_start_fragment.sil

@@ -0,0 +1,21 @@
+// RUN: not --crash %target-swift-frontend %s -sil-verify-all -g -emit-sil
+import Builtin
+import Swift
+
+struct MyStruct {
+  var x: Builtin.Int64
+  var y: Builtin.Int64
+}
+
+sil_scope 1 { loc "file.swift":7:6 parent @test_fragment : $@convention(thin) () -> () }
+
+sil hidden @test_fragment : $@convention(thin) () -> () {
+bb0:
+  %0 = alloc_stack $MyStruct, var, name "my_struct", loc "file.swift":8:9, scope 1
+  %1 = struct_element_addr %0 : $*MyStruct, #MyStruct.x, loc "file.swift":9:17, scope 1
+  // every op_fragment should be the last di-expression operand
+  debug_value %1 : $*Builtin.Int64, var, name "my_struct", expr op_deref:op_fragment:#MyStruct.y:op_constu:42:op_plus
+  dealloc_stack %0 : $*MyStruct
+  %r = tuple()
+  return %r : $()
+}