[clang] [clang][DebugInfo] Attach DW_AT_const_value to static data-member definitions if available (PR #72730)

[Michael Buch via cfe-commits]

https://github.com/Michael137 updated https://github.com/llvm/llvm-project/pull/72730

>From 6dcb09dcc50a9b9e92640412242927b3e226929e Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Sat, 18 Nov 2023 00:20:05 +0000
Subject: [PATCH 1/4] [clang][DebugInfo][NFC] Create
 evaluateConstantInitializer helper function

---
 clang/lib/CodeGen/CGDebugInfo.cpp | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 0b52d99ad07f164..4840581b5d03f89 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -69,6 +69,19 @@ static uint32_t getDeclAlignIfRequired(const Decl *D, const ASTContext &Ctx) {
   return D->hasAttr<AlignedAttr>() ? D->getMaxAlignment() : 0;
 }
 
+APValue const * evaluateConstantInitializer(clang::VarDecl const * VD) {
+  assert (VD != nullptr);
+
+  VD = VD->getCanonicalDecl();
+  if (!VD)
+    return nullptr;
+
+  if (!VD->hasConstantInitialization() || !VD->hasInit())
+    return nullptr;
+
+  return VD->evaluateValue();
+}
+
 CGDebugInfo::CGDebugInfo(CodeGenModule &CGM)
     : CGM(CGM), DebugKind(CGM.getCodeGenOpts().getDebugInfo()),
       DebugTypeExtRefs(CGM.getCodeGenOpts().DebugTypeExtRefs),
@@ -5596,14 +5609,11 @@ void CGDebugInfo::EmitGlobalVariable(const VarDecl *VD) {
   if (VD->hasAttr<NoDebugAttr>())
     return;
 
-  if (!VD->hasInit())
-    return;
-
   const auto CacheIt = DeclCache.find(VD);
   if (CacheIt != DeclCache.end())
     return;
 
-  auto const *InitVal = VD->evaluateValue();
+  auto const * InitVal = evaluateConstantInitializer(VD);
   if (!InitVal)
     return;
 

>From fcc6e19d108798fb18c1973e4d4cc3800da07f9f Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Sat, 18 Nov 2023 00:52:24 +0000
Subject: [PATCH 2/4] fixup! clang-format

---
 clang/lib/CodeGen/CGDebugInfo.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 4840581b5d03f89..9bba6e6b13e9318 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -69,8 +69,8 @@ static uint32_t getDeclAlignIfRequired(const Decl *D, const ASTContext &Ctx) {
   return D->hasAttr<AlignedAttr>() ? D->getMaxAlignment() : 0;
 }
 
-APValue const * evaluateConstantInitializer(clang::VarDecl const * VD) {
-  assert (VD != nullptr);
+APValue const *evaluateConstantInitializer(clang::VarDecl const *VD) {
+  assert(VD != nullptr);
 
   VD = VD->getCanonicalDecl();
   if (!VD)
@@ -5613,7 +5613,7 @@ void CGDebugInfo::EmitGlobalVariable(const VarDecl *VD) {
   if (CacheIt != DeclCache.end())
     return;
 
-  auto const * InitVal = evaluateConstantInitializer(VD);
+  auto const *InitVal = evaluateConstantInitializer(VD);
   if (!InitVal)
     return;
 

>From 148ab1793a866111060f77807ff065040fad92d8 Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Sat, 18 Nov 2023 00:22:06 +0000
Subject: [PATCH 3/4] [clang][DebugInfo] Attach DW_AT_const_value to static
 data-member definitions if available

---
 clang/lib/CodeGen/CGDebugInfo.cpp                      | 10 ++++++++--
 .../CodeGenCXX/debug-info-static-inline-member.cpp     |  2 +-
 clang/test/CodeGenCXX/inline-dllexport-member.cpp      |  2 +-
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 9bba6e6b13e9318..e01c57baef19931 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -5516,11 +5516,17 @@ void CGDebugInfo::EmitGlobalVariable(llvm::GlobalVariable *Var,
     }
     AppendAddressSpaceXDeref(AddressSpace, Expr);
 
+    llvm::DIExpression *E = nullptr;
+    if (Expr.empty()) {
+      if (auto const *InitVal = evaluateConstantInitializer(D))
+        E = createConstantValueExpression(D, *InitVal);
+    } else
+      E = DBuilder.createExpression(Expr);
+
     llvm::DINodeArray Annotations = CollectBTFDeclTagAnnotations(D);
     GVE = DBuilder.createGlobalVariableExpression(
         DContext, DeclName, LinkageName, Unit, LineNo, getOrCreateType(T, Unit),
-        Var->hasLocalLinkage(), true,
-        Expr.empty() ? nullptr : DBuilder.createExpression(Expr),
+        Var->hasLocalLinkage(), true, E,
         getOrCreateStaticDataMemberDeclarationOrNull(D), TemplateParameters,
         Align, Annotations);
     Var->addDebugInfo(GVE);
diff --git a/clang/test/CodeGenCXX/debug-info-static-inline-member.cpp b/clang/test/CodeGenCXX/debug-info-static-inline-member.cpp
index f2d4d9408a8297a..950ea9b302b290c 100644
--- a/clang/test/CodeGenCXX/debug-info-static-inline-member.cpp
+++ b/clang/test/CodeGenCXX/debug-info-static-inline-member.cpp
@@ -43,7 +43,7 @@ int main() {
 // CHECK:      @{{.*}}cexpr_struct_with_addr{{.*}} = 
 // CHECK-SAME    !dbg ![[EMPTY_GLOBAL:[0-9]+]]
 
-// CHECK:      !DIGlobalVariableExpression(var: ![[INT_VAR:[0-9]+]], expr: !DIExpression())
+// CHECK:      !DIGlobalVariableExpression(var: ![[INT_VAR:[0-9]+]], expr: !DIExpression(DW_OP_constu, 25, DW_OP_stack_value))
 // CHECK:      ![[INT_VAR]] = distinct !DIGlobalVariable(name: "cexpr_int_with_addr", linkageName:
 // CHECK-SAME:                isLocal: false, isDefinition: true, declaration: ![[INT_DECL:[0-9]+]])
 
diff --git a/clang/test/CodeGenCXX/inline-dllexport-member.cpp b/clang/test/CodeGenCXX/inline-dllexport-member.cpp
index d6b004d66dc6cbd..6bc01599c466780 100644
--- a/clang/test/CodeGenCXX/inline-dllexport-member.cpp
+++ b/clang/test/CodeGenCXX/inline-dllexport-member.cpp
@@ -7,7 +7,7 @@ struct __declspec(dllexport) s {
   static const unsigned int ui = 0;
 };
 
-// CHECK: [[UI]] = !DIGlobalVariableExpression(var: [[UIV:.*]], expr: !DIExpression())
+// CHECK: [[UI]] = !DIGlobalVariableExpression(var: [[UIV:.*]], expr: !DIExpression(DW_OP_constu, 0, DW_OP_stack_value))
 // CHECK: [[UIV]] = distinct !DIGlobalVariable(name: "ui", linkageName: "?ui at s@@2IB", scope: ![[SCOPE:[0-9]+]],
 // CHECK: ![[SCOPE]] = distinct !DICompileUnit(
 

>From d654d67012fa3370904c440a7045885d237b2389 Mon Sep 17 00:00:00 2001
From: Michael Buch <michaelbuch12 at gmail.com>
Date: Sat, 18 Nov 2023 00:55:01 +0000
Subject: [PATCH 4/4] fixup! make helper static

---
 clang/lib/CodeGen/CGDebugInfo.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index e01c57baef19931..b0460c93acb4f67 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -69,7 +69,7 @@ static uint32_t getDeclAlignIfRequired(const Decl *D, const ASTContext &Ctx) {
   return D->hasAttr<AlignedAttr>() ? D->getMaxAlignment() : 0;
 }
 
-APValue const *evaluateConstantInitializer(clang::VarDecl const *VD) {
+static APValue const *evaluateConstantInitializer(clang::VarDecl const *VD) {
   assert(VD != nullptr);
 
   VD = VD->getCanonicalDecl();