DebugInfo: Make DICompositeTypes distinct most of the time

Since elements of most kinds of DICompositeType have back references,
most are involved in uniquing cycles.  Except via the ODR 'identifier:'
field, which doesn't care about the storage type (see r266549),
they have no hope of being uniqued.

Distinct nodes are far more efficient, so use them for most kinds of
DICompositeType definitions (i.e., when DIType::isForwardDecl is false).
The exceptions:

  - DW_TAG_array_type, since their elements never have back-references
    and they never have ODR 'identifier:' fields;

  - DW_TAG_enumeration_type when there is no ODR 'identifier:' field,
    since their elements usually don't have back-references.

This breaks the last major uniquing cycle I'm aware of in the debug info
graph.  The impact won't be enormous for C++ because references to
ODR-uniqued nodes still use string-based DITypeRefs; but this should
prevent a regression in C++ when we drop the string-based references.

This wouldn't have been reasonable until r266549, when composite types
stopped relying on being uniqued by structural equivalence to prevent
blow-ups at LTO time.

llvm-svn: 266556

12 files changed, 46 insertions, 22 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 6fd0032f84c..ae95dd8ed66 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -2374,6 +2374,30 @@ llvm::DICompositeType *CGDebugInfo::CreateLimitedType(const RecordType *Ty) {
       getTagForRecord(RD), RDName, RDContext, DefUnit, Line, 0, Size, Align, 0,
       FullName);
 
+  // Elements of composite types usually have back to the type, creating
+  // uniquing cycles.  Distinct nodes are more efficient.
+  switch (RealDecl->getTag()) {
+  default:
+    llvm_unreachable("invalid composite type tag");
+
+  case llvm::dwarf::DW_TAG_array_type:
+  case llvm::dwarf::DW_TAG_enumeration_type:
+    // Array elements and most enumeration elements don't have back references,
+    // so they don't tend to be involved in uniquing cycles and there is some
+    // chance of merging them when linking together two modules.  Only make
+    // them distinct if they are ODR-uniqued.
+    if (FullName.empty())
+      break;
+
+  case llvm::dwarf::DW_TAG_structure_type:
+  case llvm::dwarf::DW_TAG_union_type:
+  case llvm::dwarf::DW_TAG_class_type:
+    // Immediatley resolve to a distinct node.
+    RealDecl =
+        llvm::MDNode::replaceWithDistinct(llvm::TempDICompositeType(RealDecl));
+    break;
+  }
+
   RegionMap[Ty->getDecl()].reset(RealDecl);
   TypeCache[QualType(Ty, 0).getAsOpaquePtr()].reset(RealDecl);
 
diff --git a/clang/test/CodeGenCXX/debug-info-anon-union-vars.cpp b/clang/test/CodeGenCXX/debug-info-anon-union-vars.cpp
index 80742250d84..b844d429447 100644
--- a/clang/test/CodeGenCXX/debug-info-anon-union-vars.cpp
+++ b/clang/test/CodeGenCXX/debug-info-anon-union-vars.cpp
@@ -56,7 +56,7 @@ void instantiate(int x) {
 // CHECK: !DILocalVariable(
 // CHECK-NOT: name:
 // CHECK: type: ![[UNION:[0-9]+]]
-// CHECK: ![[UNION]] = !DICompositeType(tag: DW_TAG_union_type,
+// CHECK: ![[UNION]] = distinct !DICompositeType(tag: DW_TAG_union_type,
 // CHECK-NOT: name:
 // CHECK: elements
 // CHECK: !DIDerivedType(tag: DW_TAG_member, name: "i", scope: ![[UNION]],
diff --git a/clang/test/CodeGenCXX/debug-info-artificial-arg.cpp b/clang/test/CodeGenCXX/debug-info-artificial-arg.cpp
index c840df672aa..e927dc5d734 100644
--- a/clang/test/CodeGenCXX/debug-info-artificial-arg.cpp
+++ b/clang/test/CodeGenCXX/debug-info-artificial-arg.cpp
@@ -22,7 +22,7 @@ int main(int argc, char **argv) {
   A reallyA (500);
 }
 
-// CHECK: ![[CLASSTYPE:.*]] = !DICompositeType(tag: DW_TAG_class_type, name: "A",
+// CHECK: ![[CLASSTYPE:.*]] = distinct !DICompositeType(tag: DW_TAG_class_type, name: "A",
 // CHECK-SAME:                                 identifier: "_ZTS1A"
 // CHECK: ![[ARTARG:.*]] = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !"_ZTS1A",
 // CHECK-SAME:                            DIFlagArtificial
diff --git a/clang/test/CodeGenCXX/debug-info-class.cpp b/clang/test/CodeGenCXX/debug-info-class.cpp
index ed52fd05238..ece5c945449 100644
--- a/clang/test/CodeGenCXX/debug-info-class.cpp
+++ b/clang/test/CodeGenCXX/debug-info-class.cpp
@@ -101,7 +101,7 @@ int main(int argc, char **argv) {
 
 // CHECK: ![[INT:[0-9]+]] = !DIBasicType(name: "int"
 
-// CHECK: [[C:![0-9]*]] = !DICompositeType(tag: DW_TAG_structure_type, name: "C",
+// CHECK: [[C:![0-9]*]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "C",
 // CHECK-NOT:                              DIFlagFwdDecl
 // CHECK-SAME:                             elements: [[C_MEM:![0-9]*]]
 // CHECK-SAME:                             vtableHolder: !"_ZTS1C"
diff --git a/clang/test/CodeGenCXX/debug-info-template-limit.cpp b/clang/test/CodeGenCXX/debug-info-template-limit.cpp
index 5c4ac0cc3e1..7e3a4a6959c 100644
--- a/clang/test/CodeGenCXX/debug-info-template-limit.cpp
+++ b/clang/test/CodeGenCXX/debug-info-template-limit.cpp
@@ -1,7 +1,7 @@
 // RUN: %clang_cc1 -emit-llvm -debug-info-kind=limited -triple %itanium_abi_triple %s -o - | FileCheck %s
 
 // Check that this pointer type is TC<int>
-// CHECK: ![[LINE:[0-9]+]] = !DICompositeType(tag: DW_TAG_class_type, name: "TC<int>"{{.*}}, identifier: "_ZTS2TCIiE")
+// CHECK: ![[LINE:[0-9]+]] = distinct !DICompositeType(tag: DW_TAG_class_type, name: "TC<int>"{{.*}}, identifier: "_ZTS2TCIiE")
 // CHECK: !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !"_ZTS2TCIiE"
 
 template<typename T>
diff --git a/clang/test/CodeGenCXX/debug-info-template-member.cpp b/clang/test/CodeGenCXX/debug-info-template-member.cpp
index a6ba82aa943..dcc464629fd 100644
--- a/clang/test/CodeGenCXX/debug-info-template-member.cpp
+++ b/clang/test/CodeGenCXX/debug-info-template-member.cpp
@@ -24,7 +24,7 @@ inline int add3(int x) {
 // CHECK-SAME:                         type: [[FOO_FUNC_TYPE:![0-9]*]]
 // CHECK: [[FOO_FUNC_TYPE]] = !DISubroutineType(types: [[FOO_FUNC_PARAMS:![0-9]*]])
 // CHECK: [[FOO_FUNC_PARAMS]] = !{null, !{{[0-9]*}}, !"[[OUTER_FOO_INNER_ID:.*]]"}
-// CHECK: !{{[0-9]*}} = !DICompositeType(tag: DW_TAG_structure_type, name: "inner"{{.*}}, identifier: "[[OUTER_FOO_INNER_ID]]")
+// CHECK: !{{[0-9]*}} = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "inner"{{.*}}, identifier: "[[OUTER_FOO_INNER_ID]]")
 
 // CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "virt<elem>"
 // CHECK-SAME:             elements: [[VIRT_MEM:![0-9]*]]
@@ -34,7 +34,7 @@ inline int add3(int x) {
 // CHECK: [[VIRT_TEMP_PARAM]] = !{[[VIRT_T:![0-9]*]]}
 // CHECK: [[VIRT_T]] = !DITemplateTypeParameter(name: "T", type: !"_ZTS4elem")
 
-// CHECK: [[C:![0-9]*]] = !DICompositeType(tag: DW_TAG_structure_type, name: "MyClass"
+// CHECK: [[C:![0-9]*]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "MyClass"
 // CHECK-SAME:                             elements: [[C_MEM:![0-9]*]]
 // CHECK-SAME:                             vtableHolder: !"_ZTS7MyClass"
 // CHECK-SAME:                             identifier: "_ZTS7MyClass")
@@ -43,7 +43,7 @@ inline int add3(int x) {
 
 // CHECK: [[C_FUNC]] = !DISubprogram(name: "func",{{.*}} line: 7,
 
-// CHECK: [[ELEM:![0-9]*]] = !DICompositeType(tag: DW_TAG_structure_type, name: "elem"
+// CHECK: [[ELEM:![0-9]*]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "elem"
 // CHECK-SAME:                                elements: [[ELEM_MEM:![0-9]*]]
 // CHECK-SAME:                                identifier: "_ZTS4elem"
 // CHECK: [[ELEM_MEM]] = !{[[ELEM_X:![0-9]*]]}
diff --git a/clang/test/CodeGenCXX/debug-info-template-quals.cpp b/clang/test/CodeGenCXX/debug-info-template-quals.cpp
index 1e8bdb1ad71..881bb0e2005 100644
--- a/clang/test/CodeGenCXX/debug-info-template-quals.cpp
+++ b/clang/test/CodeGenCXX/debug-info-template-quals.cpp
@@ -15,7 +15,7 @@ void foo (const char *c) {
   str.assign(c, str);
 }
 
-// CHECK: [[BS:.*]] = !DICompositeType(tag: DW_TAG_structure_type, name: "basic_string<char>"
+// CHECK: [[BS:.*]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "basic_string<char>"
 // CHECK-SAME:                         line: 4
 // CHECK-SAME:                         size: 8, align: 8
 // CHECK: [[TYPE:![0-9]*]] = !DISubroutineType(types: [[ARGS:.*]])
diff --git a/clang/test/CodeGenCXX/debug-info-template.cpp b/clang/test/CodeGenCXX/debug-info-template.cpp
index 74adef9a5f7..569357c0619 100644
--- a/clang/test/CodeGenCXX/debug-info-template.cpp
+++ b/clang/test/CodeGenCXX/debug-info-template.cpp
@@ -6,7 +6,7 @@
 // CHECK: [[RETAIN]] = !{!{{[0-9]]*}}, [[FOO:![0-9]*]],
 
 
-// CHECK: [[TC:![0-9]*]] = !DICompositeType(tag: DW_TAG_structure_type, name: "TC<unsigned int, 2, &glb, &foo::e, &foo::f, &foo::g, 1, 2, 3>"
+// CHECK: [[TC:![0-9]*]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "TC<unsigned int, 2, &glb, &foo::e, &foo::f, &foo::g, 1, 2, 3>"
 // CHECK-SAME:                              templateParams: [[TCARGS:![0-9]*]]
 // CHECK: [[TCARGS]] = !{[[TCARG1:![0-9]*]], [[TCARG2:![0-9]*]], [[TCARG3:![0-9]*]], [[TCARG4:![0-9]*]], [[TCARG5:![0-9]*]], [[TCARG6:![0-9]*]], [[TCARG7:![0-9]*]]}
 //
@@ -48,7 +48,7 @@
 // We could just emit a declaration of 'foo' here, rather than the entire
 // definition (same goes for any time we emit a member (function or data)
 // pointer type)
-// CHECK: [[FOO]] = !DICompositeType(tag: DW_TAG_structure_type, name: "foo", {{.*}}identifier: "_ZTS3foo")
+// CHECK: [[FOO]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "foo", {{.*}}identifier: "_ZTS3foo")
 // CHECK: !DISubprogram(name: "f", linkageName: "_ZN3foo1fEv", {{.*}}type: [[FTYPE:![0-9]*]]
 //
 
diff --git a/clang/test/CodeGenCXX/debug-lambda-expressions.cpp b/clang/test/CodeGenCXX/debug-lambda-expressions.cpp
index 3efdee54c98..985234f481f 100644
--- a/clang/test/CodeGenCXX/debug-lambda-expressions.cpp
+++ b/clang/test/CodeGenCXX/debug-lambda-expressions.cpp
@@ -23,7 +23,7 @@ int d(int x) { D y[10]; return [x,y] { return y[x].x; }(); }
 // CHECK: !DIGlobalVariable(name: "cvar"
 // CHECK-SAME:              line: [[CVAR_LINE:[0-9]+]]
 // CHECK-SAME:              type: ![[CVAR_T:[0-9]+]]
-// CHECK: ![[CVAR_T]] = !DICompositeType(tag: DW_TAG_class_type
+// CHECK: ![[CVAR_T]] = distinct !DICompositeType(tag: DW_TAG_class_type
 // CHECK-SAME:                           line: [[CVAR_LINE]],
 // CHECK-SAME:                           elements: ![[CVAR_ARGS:[0-9]+]]
 // CHECK: ![[CVAR_ARGS]] = !{!{{[0-9]+}}}
@@ -32,7 +32,7 @@ int d(int x) { D y[10]; return [x,y] { return y[x].x; }(); }
 // CHECK: !DIGlobalVariable(name: "var"
 // CHECK-SAME:              line: [[VAR_LINE:[0-9]+]]
 // CHECK-SAME:              type: ![[VAR_T:[0-9]+]]
-// CHECK: ![[VAR_T]] = !DICompositeType(tag: DW_TAG_class_type
+// CHECK: ![[VAR_T]] = distinct !DICompositeType(tag: DW_TAG_class_type
 // CHECK-SAME:                          line: [[VAR_LINE]],
 // CHECK-SAME:                          elements: ![[VAR_ARGS:[0-9]+]]
 // CHECK: ![[VAR_ARGS]] = !{!{{[0-9]+}}}
@@ -41,7 +41,7 @@ int d(int x) { D y[10]; return [x,y] { return y[x].x; }(); }
 // CHECK: ![[A_FUNC:.*]] = distinct !DISubprogram(name: "a"{{.*}}, line: [[A_LINE:[0-9]+]]{{.*}}, isDefinition: true
 
 // Back to A. -- 78
-// CHECK: ![[LAM_A:.*]] = !DICompositeType(tag: DW_TAG_class_type{{.*}}, scope: ![[A_FUNC]]{{.*}}, line: [[A_LINE]],
+// CHECK: ![[LAM_A:.*]] = distinct !DICompositeType(tag: DW_TAG_class_type{{.*}}, scope: ![[A_FUNC]]{{.*}}, line: [[A_LINE]],
 // CHECK-SAME:                             elements: ![[LAM_A_ARGS:[0-9]+]]
 // CHECK: ![[LAM_A_ARGS]] = !{![[CON_LAM_A:[0-9]+]]}
 // CHECK: ![[CON_LAM_A]] = !DISubprogram(name: "operator()"
@@ -53,7 +53,7 @@ int d(int x) { D y[10]; return [x,y] { return y[x].x; }(); }
 // CHECK: ![[B_FUNC:.*]] = distinct !DISubprogram(name: "b"{{.*}}, line: [[B_LINE:[0-9]+]]{{.*}}, isDefinition: true
 
 // Back to B. -- 67
-// CHECK: ![[LAM_B:.*]] = !DICompositeType(tag: DW_TAG_class_type{{.*}}, scope: ![[B_FUNC]]{{.*}}, line: [[B_LINE]],
+// CHECK: ![[LAM_B:.*]] = distinct !DICompositeType(tag: DW_TAG_class_type{{.*}}, scope: ![[B_FUNC]]{{.*}}, line: [[B_LINE]],
 // CHECK-SAME:                             elements: ![[LAM_B_ARGS:[0-9]+]]
 // CHECK: ![[LAM_B_ARGS]] = !{![[CAP_B:[0-9]+]], ![[CON_LAM_B:[0-9]+]]}
 // CHECK: ![[CAP_B]] = !DIDerivedType(tag: DW_TAG_member, name: "x"
@@ -69,7 +69,7 @@ int d(int x) { D y[10]; return [x,y] { return y[x].x; }(); }
 // CHECK: ![[C_FUNC:.*]] = distinct !DISubprogram(name: "c"{{.*}}, line: [[C_LINE:[0-9]+]]{{.*}}, isDefinition: true
 
 // Back to C. -- 55
-// CHECK: ![[LAM_C:.*]] = !DICompositeType(tag: DW_TAG_class_type{{.*}}, scope: ![[C_FUNC]]{{.*}}, line: [[C_LINE]],
+// CHECK: ![[LAM_C:.*]] = distinct !DICompositeType(tag: DW_TAG_class_type{{.*}}, scope: ![[C_FUNC]]{{.*}}, line: [[C_LINE]],
 // CHECK-SAME:                             elements: ![[LAM_C_ARGS:[0-9]+]]
 // CHECK: ![[LAM_C_ARGS]] = !{![[CAP_C:[0-9]+]], ![[CON_LAM_C:[0-9]+]]}
 // CHECK: ![[CAP_C]] = !DIDerivedType(tag: DW_TAG_member, name: "x"
@@ -86,7 +86,7 @@ int d(int x) { D y[10]; return [x,y] { return y[x].x; }(); }
 // CHECK: ![[D_FUNC:.*]] = distinct !DISubprogram(name: "d"{{.*}}, line: [[D_LINE:[0-9]+]]{{.*}}, isDefinition: true
 
 // Back to D. -- 24
-// CHECK: ![[LAM_D:.*]] = !DICompositeType(tag: DW_TAG_class_type{{.*}}, scope: ![[D_FUNC]]{{.*}}, line: [[D_LINE]],
+// CHECK: ![[LAM_D:.*]] = distinct !DICompositeType(tag: DW_TAG_class_type{{.*}}, scope: ![[D_FUNC]]{{.*}}, line: [[D_LINE]],
 // CHECK-SAME:                             elements: ![[LAM_D_ARGS:[0-9]+]]
 // CHECK: ![[LAM_D_ARGS]] = !{![[CAP_D_X:[0-9]+]], ![[CAP_D_Y:[0-9]+]], ![[CON_LAM_D:[0-9]+]]}
 // CHECK: ![[CAP_D_X]] = !DIDerivedType(tag: DW_TAG_member, name: "x"
diff --git a/clang/test/Modules/ExtDebugInfo.cpp b/clang/test/Modules/ExtDebugInfo.cpp
index 3b4547a87e0..6c38e7f464a 100644
--- a/clang/test/Modules/ExtDebugInfo.cpp
+++ b/clang/test/Modules/ExtDebugInfo.cpp
@@ -91,11 +91,11 @@ void foo() {
 
 // CHECK: !DIGlobalVariable(name: "GlobalUnion",
 // CHECK-SAME:              type: ![[GLOBAL_UNION:[0-9]+]]
-// CHECK: ![[GLOBAL_UNION]] = !DICompositeType(tag: DW_TAG_union_type,
+// CHECK: ![[GLOBAL_UNION]] = distinct !DICompositeType(tag: DW_TAG_union_type,
 // CHECK-SAME:                elements: !{{[0-9]+}})
 // CHECK: !DIGlobalVariable(name: "GlobalStruct",
 // CHECK-SAME:              type: ![[GLOBAL_STRUCT:[0-9]+]]
-// CHECK: ![[GLOBAL_STRUCT]] = !DICompositeType(tag: DW_TAG_structure_type,
+// CHECK: ![[GLOBAL_STRUCT]] = distinct !DICompositeType(tag: DW_TAG_structure_type,
 // CHECK-SAME:                elements: !{{[0-9]+}})
 
 // CHECK: !DIGlobalVariable(name: "anon",
diff --git a/clang/test/Modules/ExtDebugInfo.m b/clang/test/Modules/ExtDebugInfo.m
index d758bfda831..3b907ac729a 100644
--- a/clang/test/Modules/ExtDebugInfo.m
+++ b/clang/test/Modules/ExtDebugInfo.m
@@ -32,12 +32,12 @@ int foo(ObjCClass *c) {
 // CHECK: !DIGlobalVariable(name: "GlobalUnion",
 // CHECK-SAME:              type: ![[GLOBAL_UNION:[0-9]+]]
 // CHECK: ![[MOD:.*]] = !DIModule(scope: null, name: "DebugObjC
-// CHECK: ![[GLOBAL_UNION]] = !DICompositeType(tag: DW_TAG_union_type,
+// CHECK: ![[GLOBAL_UNION]] = distinct !DICompositeType(tag: DW_TAG_union_type,
 // CHECK-SAME:                elements: !{{[0-9]+}})
 
 // CHECK: !DIGlobalVariable(name: "GlobalStruct",
 // CHECK-SAME:              type: ![[GLOBAL_STRUCT:[0-9]+]]
-// CHECK: ![[GLOBAL_STRUCT]] = !DICompositeType(tag: DW_TAG_structure_type,
+// CHECK: ![[GLOBAL_STRUCT]] = distinct !DICompositeType(tag: DW_TAG_structure_type,
 // CHECK-SAME:                elements: !{{[0-9]+}})
 
 // CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "TypedefUnion",
diff --git a/clang/test/Modules/ModuleDebugInfo.m b/clang/test/Modules/ModuleDebugInfo.m
index 02ae93feb79..360db919ab9 100644
--- a/clang/test/Modules/ModuleDebugInfo.m
+++ b/clang/test/Modules/ModuleDebugInfo.m
@@ -50,7 +50,7 @@
 // CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "FwdDeclared"
 // CHECK-SAME:             elements:
 
-// CHECK: ![[TD_UNION:.*]] = !DICompositeType(tag: DW_TAG_union_type,
+// CHECK: ![[TD_UNION:.*]] = distinct !DICompositeType(tag: DW_TAG_union_type,
 // CHECK-NOT:              name:
 // CHECK-SAME:             elements:
 // CHECK-SAME:             )
@@ -61,7 +61,7 @@
 // CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "TypedefEnum",
 // CHECK-SAME:           baseType: ![[TD_ENUM:.*]])
 
-// CHECK: ![[TD_STRUCT:.*]] = !DICompositeType(tag: DW_TAG_structure_type,
+// CHECK: ![[TD_STRUCT:.*]] = distinct !DICompositeType(tag: DW_TAG_structure_type,
 // CHECK-NOT:              name:
 // CHECK-SAME:             elements:
 // CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "TypedefStruct",